May 2011 

Emission Estimation Protocol 

for Petroleum Refineries 

Version 2.1.1 

Final ICR Version – Corrected 

Version 2.1: Final ICR Version 

Form Approved: 03/28/2011 

OMB Control No.: 2060-0657 

Approval Expires: 03/31/2014 

Submitted to: 

Office of Air Quality Planning and Standards 

U.S. Environmental Protection Agency 

Research Triangle Park, NC 27711 

Submitted by: 

RTI International 

3040 Cornwallis Road 

Research Triangle Park, NC 27709-2194 
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Table of Contents 

1. Introduction ......................................................................................................................................... 1-1

1.1 Completeness ............................................................................................................................ 1-1

1.2 Data Quality .............................................................................................................................. 1-9

1.3 Calculations and Significant Digits ........................................................................................ 1-10

2. Equipment Leaks ................................................................................................................................. 2-1

2.1 Methodology Rank 1 for Equipment Leaks.............................................................................. 2-2

2.2 Methodology Rank 2 for Equipment Leaks.............................................................................. 2-3

2.2.1 Speciating Equipment Leak Emissions ....................................................................... 2-5

2.2.2 Calculating Hourly and Annual Equipment Leak Emissions ..................................... 2-7

2.3 Methodology Rank 3 for Equipment Leaks............................................................................ 2-10

2.3.1 Speciating Equipment Leak Emissions ..................................................................... 2-12

2.3.2 Calculating Hourly and Annual Equipment Leak Emissions ................................... 2-12

2.4 Methodology Ranks 4 and 5 for Equipment Leaks ................................................................ 2-13

2.4.1 Speciating Equipment Leak Emissions ..................................................................... 2-14

2.4.2 Calculating Hourly and Annual Equipment Leak Emissions ................................... 2-17

3. Storage Tanks ...................................................................................................................................... 3-1

3.1 Methodology Rank 1 for Storage Tanks ................................................................................... 3-1

3.2 Methodology Rank 2 for Storage Tanks ................................................................................... 3-2

3.3 Methodology Rank 3 for Storage Tanks ................................................................................... 3-4

4. Stationary Combustion Sources .......................................................................................................... 4-1

4.1 Methodology Rank 1 for Stationary Combustion Sources ....................................................... 4-2

4.2 Methodology Rank 2 for Stationary Combustion Sources ....................................................... 4-5

4.3 Methodology Rank 3A for Stationary Combustion Sources .................................................... 4-9

4.4 Methodology Rank 3B for Stationary Combustion Sources .................................................. 4-10

4.5 Methodology Rank 4 for Stationary Combustion Sources ..................................................... 4-11

4.5.1 Default Emission Factors for Process Heaters .......................................................... 4-12

4.5.2 Default Emission Factor for Internal Combustion Engines ...................................... 4-18

4.5.3 Default Emission Factors for Combustion Turbines ................................................. 4-18

5. Process Vents ...................................................................................................................................... 5-1

5.1 Catalytic Cracking Units .......................................................................................................... 5-1

5.1.1 Methodology Ranks 1 and 2 for Catalytic Cracking Units ......................................... 5-2

5.1.2 Methodology Ranks 3 and 4 for Catalytic Cracking Units ......................................... 5-2

5.1.3 Methodology Rank 5A for CCU Metal HAP Emissions Estimates ............................ 5-7

5.1.4 Methodology Rank 5B for Catalytic Cracking Units ................................................ 5-10

5.2 Fluid Coking Units ................................................................................................................. 5-11

5.2.1 Methodology Ranks 1 and 2 for Fluid Coking Units ................................................ 5-12

5.2.2 Methodology Ranks 3 and 4 for Fluid Coking Units ................................................ 5-12

5.2.3 Methodology Rank 5 for Fluid Coking Units ........................................................... 5-12

5.3 Delayed Coking Units ............................................................................................................ 5-12

5.3.1 Methodology Ranks 1 and 2 for Delayed Coking Units ........................................... 5-13

5.3.2 Methodology Ranks 3 and 4 for Delayed Coking Units ........................................... 5-13

5.3.3 Methodology Rank 5 for Delayed Coking Units ...................................................... 5-13

5.4 Catalytic Reforming Units ...................................................................................................... 5-14

5.4.1 Emissions Estimation Methodology for Catalytic Reforming Units ........................ 5-15

5.5 Sulfur Recovery Plants ........................................................................................................... 5-17

5.5.1 Methodology Ranks 1 and 2 for Sulfur Recovery Plants .......................................... 5-17
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5.5.2 Methodology Ranks 3 and 4 for Sulfur Recovery Plants .......................................... 5-17

5.5.3 Methodology Rank 5 for Sulfur Recovery Plants ..................................................... 5-18

5.6 Other Miscellaneous Process Vents ....................................................................................... 5-18

5.6.1 Hydrogen Plant Vents ............................................................................................... 5-19

5.6.2 Asphalt Plant Vents ................................................................................................... 5-19

5.6.3 Coke Calcining .......................................................................................................... 5-21

5.6.4 Blowdown Systems ................................................................................................... 5-23

5.6.5 Vacuum Producing Systems ..................................................................................... 5-24

6. Flares ................................................................................................................................................... 6-1

6.1 Methodology Rank 1 for Flares ................................................................................................ 6-2

6.2 Methodology Rank 2 for Flares ................................................................................................ 6-3

6.3 Methodology Rank 3 for Flares ................................................................................................ 6-4

6.4 Methodology Rank 4 for Flares ................................................................................................ 6-6

6.5 Methodology Ranks 5 and 6 for Flares .................................................................................... 6-7

7. Wastewater Collection and Treatment Systems .................................................................................. 7-1

7.1 Methodology Rank 1 for Wastewater Treatment Units ............................................................ 7-2

7.2 Methodology Rank 2 for Wastewater Treatment Units ............................................................ 7-2

7.2.1 Wastewater Collection Systems .................................................................................. 7-3

7.2.2 Primary Weirs ............................................................................................................. 7-5

7.2.3 Oil-Water Separators .................................................................................................. 7-5

7.2.4 Dissolved Air Flotation Units ..................................................................................... 7-6

7.2.5 Equalization Tanks ...................................................................................................... 7-6

7.2.6 Biological Treatment Units ......................................................................................... 7-6

7.2.7 Polishing Ponds ........................................................................................................... 7-8

7.2.8 Site-Specific Factors ................................................................................................... 7-8

7.2.9 Model Validation ........................................................................................................ 7-9

7.3 Methodology Rank 3 for Uncovered Units .............................................................................. 7-9

7.3.1 Engineering Estimates Based on Wastewater Treatment Plant Load ......................... 7-9

7.3.2 Engineering Estimates Based on Process Capacities .................................................. 7-9

8. Cooling Towers ................................................................................................................................... 8-1

8.1 Methodology Ranks 1 and 2 for Cooling Towers .................................................................... 8-2

8.2 Methodology Rank 3 for Cooling Towers ................................................................................ 8-8

8.3 Methodology Rank 4 for Cooling Towers .............................................................................. 8-10

8.4 Methodology Rank 5 for Cooling Towers .............................................................................. 8-11

8.4.1 VOC and Volatile Organic HAP ............................................................................... 8-12

8.4.2 Particulate Matter Emissions .................................................................................... 8-13

8.4.3 Non-volatile Organic HAP Emissions ...................................................................... 8-16

8.4.4 Chlorine Emissions ................................................................................................... 8-16

9. Loading Operations ............................................................................................................................. 9-1

9.1 Data Available on Product Composition and Properties .......................................................... 9-2

9.2 Methodology Rank 1 for Loading Operations .......................................................................... 9-2

9.3 Methodology Ranks 2 and 3 for Loading operations ............................................................... 9-3

9.4 Methodology Rank 4 for Loading operations ........................................................................... 9-4

9.4.1 AP-42 Emission Factors for “Product” or “Total Hydrocarbon” Emissions .............. 9-5

9.4.2 Estimate Uncontrolled Emissions and Speciate .......................................................... 9-6

9.4.3 Capture Efficiency ...................................................................................................... 9-6

9.4.4 Overall Control Efficiency .......................................................................................... 9-7
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10. Fugitive Dust Sources ....................................................................................................................... 10-1

11. Startup and Shutdown ....................................................................................................................... 11-1

11.1 Gaseous Process Vessel Depressurization and Purging ......................................................... 11-1

11.2 Liquid Process Vessel Depressurization and Purging ............................................................ 11-2

12. Malfunctions/Upsets .......................................................................................................................... 12-1

12.1 Control Device Malfunctions ................................................................................................. 12-2

12.2 Vessel Overpressurization ...................................................................................................... 12-3

12.3 Spills ....................................................................................................................................... 12-6

13. References ......................................................................................................................................... 13-1
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List of Figures 

Figure 2-1. Illustration of alternative methods to determine equipment leak emissions from 

routine monitoring data. ................................................................................................................ 2-8

Figure 7-1. Typical refinery wastewater treatment system. ....................................................................... 7-1

Figure 7-2. Typical refinery wastewater collection system process drainage areas. ................................. 7-4

Figure 7-3. Simplified drawing of a constituent mass balance in a biological treatment unit. .................. 7-7

List of Tables 

Table 1-1. Summary of Pollutants and Emission Sources Inclusion in a Petroleum Refinery’s 

Emission Inventory ....................................................................................................................... 1-3

Table 2-1. Summary of Equipment Leak Emission Estimates .................................................................. 2-2

Table 2-2. Equipment Leak Rate for Petroleum and SOCMI Equipment Componentsa

 ........................... 2-4

Table 2-3. Screening Ranges Emission Factorsa

 ...................................................................................... 2-11

Table 2-4. Median Equipment Leak Component Counts for Small Model Processesa

 ............................ 2-15

Table 2-5. Median Equipment Leak Component Counts for Large Model Processesa

 ............................ 2-16

Table 2-6. Refinery and SOCMI Average Component Emission Factorsa

 .............................................. 2-17

Table 2-7. Concentration of HAP in Refinery Process Unit Streamsa

 ..................................................... 2-18

Table 3-1. Summary of Typical Hierarchy of Storage Tank Emission Estimates ..................................... 3-1

Table 3-2. Default Control Efficiencies for Different VOC Control Devices ........................................... 3-4

Table 4-1. Summary of Typical Hierarchy of Stationary Combustion Source Emission Estimates .......... 4-2

Table 4-2. Molar Exhaust Volumes and Molar Heat Content of Refinery Fuel Gas Constituents ............ 4-5

Table 4-3. Summary of Emission Factors for Boilers and Process Heaters Firing Various Fuels .......... 4-13

Table 4-4. Summary of Emission Factors for Internal Combustion Engines Firing Various Fuelsa

 ....... 4-19

Table 4-5. Summary of Emission Factors for Combustion Turbines Firing Various Fuelsa

 ................... 4-23

Table 5-1. Summary of Typical Hierarchy of Process Vent Emissions Estimates .................................... 5-1

Table 5-2. Default Size Distribution for Filterable PM from CCU ........................................................... 5-6

Table 5-3. Default Ratio of Metal HAP Composition of CCU Finesa

 ....................................................... 5-8

Table 5-4. Organic HAP Emissions Factors for CCU Catalyst Regenerator Vent .................................. 5-10

Table 5-5. Average Vent Concentrations and Emissions Factors for Delayed Coking Unit Vents ......... 5-14

Table 5-6. Emissions Factors for CRU Catalyst Regeneration Vent ....................................................... 5-16

Table 5-7. Emissions Factors for Sulfur Recovery Plants ....................................................................... 5-18

Table 5-8. Emission Factors for Asphalt Blowing (U.S. EPA, 1995a) .................................................... 5-19

Table 5-9. Asphalt Blowing – Nonmethane Volatile Organic Compounds Speciationa

 .......................... 5-20

Table 5-10. Summary of Emissions Factors for Controlled Asphalt Blowing ........................................ 5-20

Table 5-11. Summary of Emissions Factors for Controlled Coke Calcining ........................................... 5-21

Table 5-12. Default Emissions Factors for Blowdown Systems .............................................................. 5-24

Table 5-13. Default Emissions Factor for Vacuum Producing Systems .................................................. 5-25

Table 6-1. Summary of Flare Emissions Estimate Methodologies ............................................................ 6-2

Table 6-2. Flare Energy Consumption-Based Emission Factors ............................................................... 6-5

Table 6-3. TCEQ Energy Consumption-Based Emission Factors for Flares ............................................. 6-5

Table 6-4. Emission Factors for Soot from Flares ..................................................................................... 6-6

Table 6-5. Flare General Emission Factorsa

 ............................................................................................... 6-8

Table 7-1. Summary of Wastewater Treatment Emission Estimates ......................................................... 7-2

Table 7-2. Critical Inputs and Chemical Properties Specific to Wastewater Collection System 

PDA Air Emission Calculations ................................................................................................... 7-5

Table 7-3. Critical Inputs, Variables, and Chemical Properties Specific to Primary Weir Air 

Emission Calculations ................................................................................................................... 7-5
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Table 7-4. Critical Inputs, Variables, and Chemical Properties Specific to Oil-Water Separators 

Air Emission Calculations ............................................................................................................ 7-5

Table 7-5. Critical Inputs, Variables, and Chemical Properties Specific to DAF Air Emission 

Calculations .................................................................................................................................. 7-6

Table 7-6. Critical Inputs, Variables, and Chemical Properties Specific to Equalization Tank Air 

Emission Calculations ................................................................................................................... 7-6

Table 7-7. Critical Inputs, Variables, and Chemical Properties Specific to Biological Treatment 

Unit Air Emission Calculations .................................................................................................... 7-8

Table 7-8. Model Process Unit Characteristics for Petroleum Refinery Wastewatera

 ............................. 7-10

Table 7-9. Refinery Wastewater Contaminant Concentrations as a Ratio to Benzene ............................ 7-10

Table 7-10. Default Mass Emission Factors for Refinery Wastewater Collection and Treatment 

Systems ....................................................................................................................................... 7-11

Table 8-1. Summary of Cooling Tower Emissions Estimation Methodologies ........................................ 8-2

Table 8-2. Data Requirements for VOC or Speciated VOC Emissions, Methodology Ranks 1 and 

2 .................................................................................................................................................... 8-3

Table 8-3. Data Requirements for Speciated Compound Emissions, Methodology Rank 3 ..................... 8-9

Table 8-4. Data Requirements for Speciated Compound Emissions, Methodology Rank 4 ................... 8-11

Table 8-5. Methodology Rank 5 Default Emission Factors ..................................................................... 8-11

Table 8-6. Data Requirements for VOC or Speciated VOC Emissions, Methodology Rank 5 ............... 8-12

Table 9-1. Summary of Loading operations Emission Estimates .............................................................. 9-2

Table 9-2. Data Requirements for VOC or Speciated Emissions, Methodology Rank 1 or 2 ................... 9-3

Table 9-3. Saturation Factorsa

 .................................................................................................................... 9-5

Table 9-4. VOC Emission Factors for Marine Vessel Loading of Gasoline at Marine Terminalsa

 ........... 9-6

Table 9-5. Capture Efficiencies for Vapor Collection Systemsa

 ................................................................ 9-7

Table 9-6. Sample Calculation Methodology Rank 4—Summary of Emissions (When Property 

Data Are Not Available) ............................................................................................................. 9-10

Table 10-1. Default Values for Fugitive Dust Emission Estimates ......................................................... 10-1

Table 12-1. Control Device Efficiency and Multiplier Factors for Control Device Malfunctions .......... 12-2
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List of Acronyms and Abbreviations 

μg/L micrograms per liter 

acfm actual cubic feet per minute 

API American Petroleum Institute 

atm atmosphere 

atm/in. of Hg atmospheres per inch of mercury 

bbl/cd barrels per calendar day 

bbl/sd barrels per stream day 

bbl/hr barrels per hour 

BID Background Information Document 

BOX test Batch test with oxygen addition (a type of aerated reactor test specified in 

Appendix C to 40 CFR Part 63) 

Btu/mol British thermal units per mole 

Btu/scf British thermal units per standard cubic feet 

BWON Benzene Waste Operations NESHAP 

CARB California Air Resources Board 

CCU catalytic cracking unit 

CEMS continuous emission monitoring system 

CERMS continuous emission rate monitoring system 

CFR Code of Federal Regulations 

CH4 methane 

Cl2 chlorine 

CO carbon monoxide 

COS carbonyl sulfide 

Cr+6 hexavalent chromium 

CRU catalytic reforming unit 

CS2 carbon disulfide 

DAF dissolved air flotation 

DIAL Differential Absorption Light Detection and Ranging 

DNF dissolved nitrogen flotation 

dscf/MMBtu dry standard cubic feet per million British thermal unit 

dscf/mol dry standard cubic feet per mole 

dscfm dry standard cubic feet per minute 

E-cat equilibrium catalyst 

EPA U.S. Environmental Protection Agency 

ESP electrostatic precipitator 

FCCU fluid catalytic cracking unit 

FCU fluid coking unit 

FID flame ionization detection 

g/hr grams per hour 
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g/mol grams per mole 

gal/bbl gallons of wastewater per barrel of capacity at a given process unit 

GC gas chromatograph 

GC/MS gas chromatography/mass spectrometry 

GHG greenhouse gases 

H2S hydrogen sulfide 

HAP hazardous air pollutants 

HCl hydrogen chloride 

hepta-CDD heptachloro-dibenzo-p-dioxin 

Hg Mercury 

hr/yr hours per year 

IAF induced air flotation 

ICR information collection request 

in. Inches 

kg TOC/hr kilograms of TOC per hour 

kg/hr kilograms per hour 

kg/hr/source kilograms per hour per source 

kg/kg-mol kilogram per kilogram mole 

kg/yr kilograms per year 

kPa kilopascals 

lb/dscf pounds per dry standard cubic foot 

lb/lb-mol pounds per pound mole 

lb/lton pounds per long ton 

lb/Mgal pounds per thousand gallons 

lb/MMbbl pounds per million barrels 

lb/MMBtu pounds per million British thermal unit 

lb/MMcf pounds per million cubic feet 

lb/ton pounds per ton 

lb/ton coke pounds per ton of petroleum coke 

LDAR leak detection and repair 

LIDAR Light Detection and Ranging 

m3

/day cubic meters per day 

m3

/min cubic meters per minute 

MACT Maximum Achievable Control Technology 

mg/kg milligrams per kilogram 

min/hr minutes per hour 

mL/min milliliters per minute 

mL-atm/mol-K milliliters-atmospheres per mole-Kelvin 

MMBtu/scf million British thermal units per standard cubic foot 

MW molecular weight 

Ni Nickel 
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NMOC nonmethane organic compounds 

NMVOC nonmethane volatile organic compounds 

NO nitric oxide 

NO2 nitrogen dioxide 

NOx nitrogen oxides 

NSPS new source performance standards 

O2 Oxygen 

OCDD octachloro-dibenzo-p-dioxin 

OCDF octachloro-dibenzo-furan 

OVA organic vapor analyzer 

PAH polycyclic aromatic hydrocarbons 

PCB polychlorinated biphenyls 

PM particulate matter 

PM10 PM emissions that are 10 μm in diameter or less 

PM10-FIL filterable (or front-half catch) portion of the PM emissions that are 10 μm in 

diameter or less 

PM10-PRI “primary” PM emissions that are 10 μm in diameter or less 

PM2.5 PM emissions that are 2.5 μm in diameter or less 

PM2.5-FIL filterable (or front-half catch) portion of the PM emissions that are 2.5 μm in 

diameter or less 

PM2.5-PRI “primary” PM emissions that are 2.5 μm in diameter or less 

PM-CON condensable PM (or back-half catch) 

POM polycyclic organic matter 

POTW publicly owned treatment works 

ppmv parts per million by volume 

ppmw parts per million by weight 

psi pounds per square inch 

psia pounds per square inch absolute 

psig pounds per square inch gauge 

QA quality assurance 

QC quality control 

scf/kg-mol standard cubic feet per kilogram mole 

scf/lb-mol standard cubic feet per pound mole 

SCR selective catalytic reduction 

SNCR selective non-catalytic reduction 

SO2 sulfur dioxide 

SRU sulfur recovery unit 

SSM startup, shutdown, or malfunction 

SV screening value 

TCCU thermal catalytic cracking unit 

TCDD tetrachlorodibenzo-p-dioxin 
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TDS total dissolved solids 

TEQ toxic equivalents 

THC total hydrocarbons 

TOC total organic compounds 

tons/hr tons per hour 

tons/kg tons per kilogram 

tons/yr tons per year 

VOC volatile organic compounds 

vol% volume percent 

WebFIRE Internet version of the Factor Information Retrieval (FIRE) data system 

WF weight fraction 

WSPA Western States Petroleum Association 

wt% weight percent 

°C degrees Celsius 

°F degrees Fahrenheit 

°R degrees Rankine 

 
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1. Introduction 

This Refinery Emissions Protocol document is intended to provide guidance and instructions to petroleum 

refinery owners and operators for the purpose of improving emission inventories as collected through the 

U.S. Environmental Protection Agency’s (EPA’s) 2011 information collection request (ICR) for the 

petroleum refining industry. This document presents a hierarchy of emission measurement or estimation 

methods for various petroleum refinery emission sources and provides a listing of pollutants for which 

emissions are anticipated for each source type. 

For each emission source, the various emission measurement or estimation methods specific to that 

source are ranked in order of preference, with “Methodology Rank 1” being the preferred method, 

followed by “Methodology Rank 2,” and so on. Refinery owners and operators are requested to use the 

highest ranked method (with Methodology Rank 1 being the highest) for which data are available. 

Methodology Ranks 1 or 2 generally rely on continuous emission measurements. When continuous 

measurement data are not available, engineering calculations or site-specific emission factors 

(Methodology Ranks 3 and 4) are specified; these methods generally need periodic, site-specific 

measurements. When site-specific measurement or test data are not available, default emission factors 

(Methodology Rank 5) are provided. Nothing in this Refinery Emissions Protocol document should be 

construed to require additional monitoring or testing by the petroleum refinery owner or operator. Thus, if 

an emission source has continuous emission measurements, these data should be used in developing the 

emission inventory for that source; however, this Refinery Emissions Protocol document does not require 

the installation and use of continuous emission measurement systems. When no measurement data are 

available, the emission factors provided in this Refinery Emissions Protocol document should be used 

when developing emission estimates for reporting in response to the petroleum refinery ICR. 

In the development of this Refinery Emissions Protocol document, EPA reviewed available source test 

data to verify or refine existing emission factors and develop new emission factors for sources that 

currently do not have default emission factors. EPA also provided guidance on characterizing and 

quantifying emissions associated with start-up, shut-down, and malfunction events. The “peer review 

draft version” (Version 1.0) of the Refinery Emissions Protocol document was posted on the EPA Web 

site (http://www.epa.gov/ttn/chief/efpac/esttools.html) on January 7, 2010, for initial public comment. 

Public comments were received from three different commenters. The “draft ICR version” (Version 2.0) 

of the Refinery Emissions Protocol document was revised to address these comments, as appropriate, and 

was made available for additional public comments prior to the implementation of the ICR. This “final 

ICR version” (Version 2.1) of the Refinery Emissions Protocol document addresses, as appropriate, any 

additional public comments received during this review period. Refinery owners and operators 

responding to the 2011 petroleum refinery ICR should check the EPA Web site 

(http://www.epa.gov/ttn/chief/efpac/esttools.html) or the refinery ICR Web site (https://refineryicr.rti.org) 

prior to preparing the emission inventory to ensure that the most recent Refinery Emissions Protocol 

document is used. 

1.1 Completeness 

Emission estimates should be provided for each emission source at the refinery, including ancillary 

sources and non-refinery process units. While this Refinery Emissions Protocol document attempts to 

identify and provide methodologies for each emission source at a typical petroleum refinery, there may be 

certain sources located at the refinery facility (i.e., that are owned or under the common control of the 

refinery owners or operators) that are not specifically addressed within the Refinery Emissions Protocol 

document. Additionally, there are sources included in this Refinery Emissions Protocol document for 

which no emission data are available to provide default (Methodology Rank 5) methods. Emission 
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estimates should be provided for every emission source present at the refinery, even for emission sources 

that are not specifically included in this Refinery Emissions Protocol document. 

Similarly, emission estimates should be provided for each pollutant (except for greenhouse gases [GHGs], 

which are required to be reported under the Mandatory Greenhouse Gas Emissions Reporting Rule [Final 

Rule, 74 FR 56260]) emitted from a given emission source. Table 1-1 provides a listing of the pollutants 

expected to be emitted by various sources described in this protocol document. Filled circles indicate 

compound/emission source pairings for which emission estimates should be developed. Hollow circles 

indicate pairings for which data may be reported (if the chemical is present or if data are available to 

speciate to that extent), but the inventory can be deemed complete without these estimates. In general, 

speciation of volatile organic compound (VOC) emissions is preferred to overall VOC emission 

measurement methods via EPA Methods 25, 25A-E, or 305, and should be provided when these data are 

readily available; however, speciation of VOC emissions is not required. While emission estimates are 

desirable for every compound/emission source paring where there is a filled circle in Table 1-1, no new 

sampling or analyses is required to provide these emission estimates. Rather available data, supplemented 

with engineering analyses (following the guidance provided in this Protocol, where applicable), may be 

used to provide the desired speciation. 

Some criteria pollutants, such as PM10 or PM2.5 have special reporting nomenclatures to indicate the 

fraction of the particulate matter (PM) emissions that are filterable or condensable (see PM Emission 

Inventory Nomenclature text box). Other criteria pollutants, such as nitrogen dioxide (NO2), are often 

determined or regulated as a combination of chemicals. For example, nitrogen oxides (NOx), is the sum of 

NO2 and nitric oxide (NO) emissions. The inclusion of these additional nomenclatures or groupings in 

Table 1-1 is not intended to suggest that these compounds are criteria pollutants, but that these 

“pollutants” should be included in the refinery emission inventory. No new sampling or analysis is 

required to provide these estimates; available data, supplemented with engineering analyses (following 

the guidance provided in this Protocol, where applicable), may be used to develop these estimates 

PM Emission Inventory Nomenclature 

PM emissions inventories have their own nomenclature and structure. A complete PM emissions inventory 

includes the following components: 

 PM10-PRI: “Primary” PM emissions that are 10 μm in diameter or less. PM10-PRI = PM10-FIL + PM-CON. 

 PM10-FIL: Filterable (or front-half catch) portion of the PM emissions that are 10 μm in diameter or less. 

 PM-CON: Condensable PM (or back-half catch). All condensable PM is assumed to be less than 2.5 microns 

(μm) in diameter (PM2.5). 

 PM2.5-PRI: “Primary” PM emissions that are 2.5 μm in diameter or less. PM2.5-PRI = PM25-FIL + PM-CON. 

 PM2.5-FIL: Filterable (or front-half catch) portion of the PM emissions that are 2.5 μm in diameter or less. 

Although a complete PM emissions inventory includes PM emissions that are 10 μm in diameter or less, some 

measurement methods also collect PM particles that are greater than 10 μm in diameter. The following 

nomenclature is used to designate PM emissions that include PM greater than 10 μm in diameter: 

 PM-PRI: “Primary” PM emissions of any particle size. PM-PRI = PM-FIL + PM-CON. 

 PM-FIL: Filterable (or front-half catch) portion of the PM emissions of any particle size. 
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Table 1-1. Summary of Pollutants and Emission Sources Inclusion 

in a Petroleum Refinery’s Emission Inventory 

CAS 

Number or 

Pollutant 

Code Substance 

Equipment Leaks Storage Tanks Stationary Combustion 

Process Vents 

Catalytic Cracking Unit Fluid Coking Unit Delayed Coking Unit Catalytic Reforming Unit Sulfur Recovery Plants Hydrogen Plant Asphalt Plant Coke Calcining Blowdown Systems Vacuum Systems Flares Wastewater Cooling Towers Product Loading Fugitive Dust Sources Startup/Shutdown Malfunctions 

Criteria Pollutants 

630-08-0 Carbon monoxide ● ● ● ● ● ● ○ ○

7439-92-1 Lead ● ● ● ○ ○ ○ ○

PM10-PRI Particulate matter (PM) 

≤ 10 micrometers (μm) ● ● ● ● ● ● ● ● ● ○ ○

PM10-FIL Filterable PM ≤ 10 μm ● ● ● ● ● ● ● ● ● ○ ○

PM25-PRI PM ≤ 2.5 μm ● ● ● ● ● ● ● ● ● ○ ○

PM25-FIL Filterable PM ≤ 2.5 μm ● ● ● ● ● ● ● ● ● ○ ○

PM-CON Condensable PM ● ● ● ● ● ● ● ● ○ ○ ○

10102-44-0 Nitrogen dioxide ● ● ● ● ● ● ○ ○

NOX Nitrogen oxides ● ● ● ● ● ● ○ ○

7446-09-5 Sulfur dioxide ● ● ● ● ● ● ● ●

VOC Volatile organic 

compounds ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

Specific VOC Constituents (Compounds listed below plus those listed under “Volatile Organic HAPs”) 

74-85-1 Ethylene ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

74-86-2 Acetylene ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

74-98-6 Propane ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

115-07-1 Propylene ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

463-49-0 Propadiene ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

106-97-8 n-Butane ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

75-28-5 Isobutane ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

106-98-9 1-Butene ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

107-01-7 2-Butene ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

115-11-7 Isobutene ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

(continued)
Version 2.1.1 

Final ICR Version – Corrected Section 1—Introduction 

1-4 

Table 1-1. Summary of Pollutants and Emission Sources Inclusion 

in a Petroleum Refinery’s Emission Inventory (continued) 

CAS 

Number 

or Pollutant 

Code Substance 

Equipment Leaks Storage Tanks Stationary Combustion 

Process Vents 

Catalytic Cracking Unit Fluid Coking Unit Delayed Coking Unit Catalytic Reforming Unit Sulfur Recovery Plants Hydrogen Plant Asphalt Plant Coke Calcining Blowdown Systems Vacuum Systems Flares Wastewater Cooling Towers Product Loading Fugitive Dust Sources Startup/Shutdown Malfunctions 

590-19-2 1,2-Butadiene ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

109-66-0 n-pentane ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

78-78-4 2-Methylbutane ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

287-92-3 Cyclopentane ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

591-95-7 1,2-Pentadiene ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

1574-41-0 1-cis-3-Pentadiene ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

2004-70-8 1-trans-3-Pentadiene ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

591-93-5 1,4-Pentadiene ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

591-96-8 2,3-Pentadiene ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

598-25-4 3-Methyl-1,2-butadiene ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

78-79-5 2-Methyl-1,3-butadiene ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

542-92-7 Cyclopentadiene ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

110-82-7 Cyclohexane ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

108-87-2 Methylcylcohexane ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

142-82-5 Heptane (and isomers) ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

111-65-9 Octane (and isomers) ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

78-93-3 Methyl ethyl ketone ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

25551-13-7 Trimethylbenzene(s) ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

Hazardous Air Pollutants (HAPs) 

Volatile Organic HAPs 

75-07-0 Acetaldehyde ○ ○ ● ● ● ● ● ○ ● ● ● ○ ○ ● ○ ○ ○ ○ ○

107-02-8 Acrolein ○ ○ ● ● ● ● ● ○ ○ ○ ● ○ ○ ● ○ ○ ○ ○ ○

62-53-3 Analine ○ ○ ● ● ● ● ● ○ ○ ○ ● ○ ○ ● ○ ○ ○ ○ ○

71-43-2 Benzene ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

74-83-9 Bromomethane ○ ○ ○ ○ 

106-99-0 1,3-Butadiene ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

75-00-3 Chloroethane ○ ○ ○ ○ ○ 

(continued)
Version 2.1.1 

Final ICR Version – Corrected Section 1—Introduction 

1-5 

Table 1-1. Summary of Pollutants and Emission Sources Inclusion 

in a Petroleum Refinery’s Emission Inventory (continued) 

CAS 

Number 

or Pollutant 

Code Substance 

Equipment Leaks Storage Tanks Stationary Combustion 

Process Vents 

Catalytic Cracking Unit Fluid Coking Unit Delayed Coking Unit Catalytic Reforming Unit Sulfur Recovery Plants Hydrogen Plant Asphalt Plant Coke Calcining Blowdown Systems Vacuum Systems Flares Wastewater Cooling Towers Product Loading Fugitive Dust Sources Startup/Shutdown Malfunctions 

67-66-3 Chloroform ○ ○ ● ○ ○ 

74-87-3 Chloromethane ○ ○ ○ ○ ○ 

98-82-8 Cumene ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

106-93-4 1,2-Dibromoethane ○ ○ ○ ○ ○ ○ 

106-46-7 1,4-Dichlorobenzene ○ ○ ○ ○ ○ ○ 

75-34-3 1,1-Dichloroethane ○ ○ ○ ○ ○ 

107-06-2 1,2-Dichloroethane ○ ○ ○ ○ ○ 

75-35-4 1,1-Dichloroethylene ○ ○ ● ○ ○ 

78-87-5 1,2-Dichloropropane ○ ○ ○ ○ ○ 

542-75-6 1,3-Dichloropropene ○ ○ ○ ○ ○ 

111-42-2 Diethanolamine ● ● ● ○ ○ ○ ○

100-41-4 Ethylbenzene ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

50-00-0 Formaldehyde ○ ○ ● ● ● ● ● ● ● ● ○ ○ ● ○ ○ ○ ● ●

67-72-1 Hexachloroethane ○ ○ ○ ○ 

110-54-3 n-Hexane ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

67-56-1 Methanol ● ● ○ ○ 

108-10-1 Methyl isobutyl ketone ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

1634-04-4 Methyl tert-butyl ether ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

100-42-5 Styrene ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

79-34-5 1,1,2,2-

Tetrachloroethane ○ ○ ● ○ ○ 

127-18-4 Tetrachloroethylene ○ ○ ● ○ ○ 

108-88-3 Toluene ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

79-00-5 1,1,2-Trichloroethane ○ ○ ● ○ ○ 

79-01-6 Trichloroethylene ○ ○ ● ○ ○ 

121-44-8 Triethylamine ● ● ● ○ ○ ○ ○

540-84-1 2,2,4-Trimethylpentane ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

593-60-2 Vinyl bromide ○ ○ ○ ○ ○ 

(continued) 
Version 2.1.1 

Final ICR Version – Corrected Section 1—Introduction 

1-6 

Table 1-1. Summary of Pollutants and Emission Sources Inclusion 

in a Petroleum Refinery’s Emission Inventory (continued) 

CAS 

Number 

or Pollutant 

Code Substance 

Equipment Leaks Storage Tanks Stationary Combustion 

Process Vents 

Catalytic Cracking Unit Fluid Coking Unit Delayed Coking Unit Catalytic Reforming Unit Sulfur Recovery Plants Hydrogen Plant Asphalt Plant Coke Calcining Blowdown Systems Vacuum Systems Flares Wastewater Cooling Towers Product Loading Fugitive Dust Sources Startup/Shutdown Malfunctions 

75-01-4 Vinyl chloride ○ ○ ● ○ ○ 

95-47-6 o-Xylene ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

108-38-3 m-Xylene ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

106-42-3 p-Xylene ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

1330-20-7 Xylenes (total) ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● ●

Semi-volatile and Non-volatile Organic HAPs (except dioxins, furans, and polychlorinated biphenyls [PCBs]) 

83-32-9 Acenaphthene POM ● ○ ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ○ ○ ● ●

208-96-8 Acenaphthylene POM ● ○ ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ○ ○ ● ●

120-12-7 Anthracene POM ● ○ ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ○ ○ ● ●

56-55-3 Benzo(a)anthracene POM ● ○ ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ○ ○ ● ●

50-32-8 Benzo(a)pyrene POM ● ○ ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ○ ○ ● ●

205-99-2 Benzo(b)fluoranthenePOM ● ○ ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ○ ○ ● ●

192-97-2 Benzo(e)pyrene POM ● ○ ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ○ ○ ● ●

191-24-2 Benzo(g,h,i)perylenePOM ● ○ ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ○ ○ ● ●

207-08-9 Benzo(k)fluoranthenePOM ● ○ ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ○ ○ ● ●

92-52-4 Biphenyl POM ● ○ ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ○ ○ ● ●

117-81-7 Bis(2-ethyl hexyl) 

phthalate ○ ● ● ○ 

91-58-7 2-ChloronaphthalenePOM ● ○ ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ○ ○ ● ●

108-39-4 m-Cresol ● ● ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ● ● ●

95-48-7 o-Cresol ● ● ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ● ● ●

106-44-5 p-Cresol ● ● ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ● ● ●

1319-77-3 Cresols (total) ● ● ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ● ● ●

218-01-9 Chrysene POM ● ○ ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ○ ○ ● ●

53-70-3 Dibenz(a,h) 

anthracenePOM ● ○ ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ○ ○ ● ●

84-74-2 di-n-Butyl phthalate ○ ● ● ○ 

84-66-2 Diethyl-phthalate ○ ● ● ○ 

(continued) 
Version 2.1.1 

Final ICR Version – Corrected Section 1—Introduction 

1-7 

Table 1-1. Summary of Pollutants and Emission Sources Inclusion 

in a Petroleum Refinery’s Emission Inventory (continued) 

CAS 

Number 

or Pollutant 

Code Substance 

Equipment Leaks Storage Tanks Stationary Combustion 

Process Vents 

Catalytic Cracking Unit Fluid Coking Unit Delayed Coking Unit Catalytic Reforming Unit Sulfur Recovery Plants Hydrogen Plant Asphalt Plant Coke Calcining Blowdown Systems Vacuum Systems Flares Wastewater Cooling Towers Product Loading Fugitive Dust Sources Startup/Shutdown Malfunctions 

57-97-6 7,12-Dimethylbenz(a) 

anthracene POM ● ○ ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ○ ○ ● ●

206-44-0 Fluoranthene POM ● ○ ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ○ ○ ● ●

86-73-7 Fluorene POM ● ○ ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ○ ○ ● ●

193-39-5 Indeno(1,2,3-cd) 

pyrenePOM ● ○ ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ○ ○ ● ●

56-49-5 3-MethylchloranthrenePOM ● ○ ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ○ ○ ● ●

91-57-6 2-Methylnaphthalene POM ● ○ ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ○ ○ ● ●

218-01-9 Chrysene POM ● ○ ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ○ ○ ● ●

91-20-3 Naphthalene POM ● ● ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ● ○ ● ●

198-55-0 Perylene POM ● ○ ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ○ ○ ● ●

85-01-8 Phenanthrene POM ● ○ ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ○ ○ ● ●

108-95-2 Phenol ● ● ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ● ● ●

129-00-0 Pyrene POM ● ○ ● ● ● ● ● ○ ○ ● ● ○ ● ● ● ● ○ ○ ● ●

Dioxins/Furans/PCBs 

1746-01-6 Dioxin: 4D 2378j ● ● ● ● ● ○ ○ ○ 

40321-76-4 Dioxin: 5D 12378j ○ ○ ○ ○ ○ ○ ○ ○ 

39227-28-6 Dioxin: 6D 123478j ○ ○ ○ ○ ○ ○ ○ ○ 

57653-85-7 Dioxin: 6D 123678j ○ ○ ○ ○ ○ ○ ○ ○ 

19408-74-3 Dioxin: 6D 123789j ○ ○ ○ ○ ○ ○ ○ ○ 

35822-46-9 Dioxin: 7D 1234678j ○ ○ ○ ○ ○ ○ ○ ○ 

3268-87-9 Dioxin: 8Dj ○ ○ ○ ○ ○ ○ ○ ○ 

132-64-9 Dibenzofurans ● ● ● ● ● ○ ○ ○ 

51207-31-9 Furan: 4F 2378k ○ ○ ○ ○ ○ ○ ○ ○ 

57117-41-6 Furan: 5F 12378k ○ ○ ○ ○ ○ ○ ○ ○ 

57117-31-4 Furan: 5F 23478k ○ ○ ○ ○ ○ ○ ○ ○ 

70648-26-9 Furan: 6F 123478k ○ ○ ○ ○ ○ ○ ○ ○ 

57117-44-9 Furan: 6F 123678k ○ ○ ○ ○ ○ ○ ○ ○ 

(continued) 
Version 2.1.1 

Final ICR Version – Corrected Section 1—Introduction 

1-8 

Table 1-1. Summary of Pollutants and Emission Sources Inclusion 

in a Petroleum Refinery’s Emission Inventory (continued) 

CAS 

Number 

or Pollutant 

Code Substance 

Equipment Leaks Storage Tanks Stationary Combustion 

Process Vents 

Catalytic Cracking Unit Fluid Coking Unit Delayed Coking Unit Catalytic Reforming Unit Sulfur Recovery Plants Hydrogen Plant Asphalt Plant Coke Calcining Blowdown Systems Vacuum Systems Flares Wastewater Cooling Towers Product Loading Fugitive Dust Sources Startup/Shutdown Malfunctions 

72918-21-9 Furan: 6F 123789k ○ ○ ○ ○ ○ ○ ○ ○ 

60851-34-5 Furan: 6F 234678k ○ ○ ○ ○ ○ ○ ○ ○ 

67562-39-4 Furan: 7F 1234678k ○ ○ ○ ○ ○ ○ ○ ○ 

55673-89-7 Furan: 7F 1234789k ○ ○ ○ ○ ○ ○ ○ ○ 

39001-02-0 Furan: 8Fk ○ ○ ○ ○ ○ ○ ○ ○ 

1336-36-3 Polychlorinated biphenyls 

(total) ● ● ● ● ● ○ ○ ○ 

Metal HAPs 

7440-36-0 Antimony ● ● ● ○ ○ ○ ○

7440-38-2 Arsenic ● ● ● ○ ○ ○ ○

7440-41-7 Beryllium ● ● ● ○ ○ ○ ○

7440-43-9 Cadmium ● ● ● ○ ○ ○ ○

18540-29-9 Chromium (hexavalent) ● ● ● ○ ○ ○ ○

7440-47-3 Chromium (total) ● ● ● ○ ○ ○ ○

7440-48-4 Cobalt ● ● ● ○ ○ ○ ○

7439-92-1 Lead ● ● ● ○ ○ ○ ○

7439-96-5 Manganese ● ● ● ○ ○ ○ ○

7439-97-6 Mercury ● ● ● ○ ○ ○ ○

7440-02-0 Nickel ● ● ● ○ ○ ○ ○

7782-49-2 Selenium ● ● ● ○ ○ ○ ○

Other Inorganic HAPs 

75-15-0 Carbon disulfide ○ ○ ○ ○ ● ○ ○ ○ ○ ○ ○ ○ ○ ○

463-58-1 Carbonyl sulfide ○ ○ ○ ○ ● ○ ○ ○ ○ ○ ○ ○ ○ ○

7782-50-5 Chlorine ● ● 

7647-01-0 Hydrogen chloride ○ ○ ○ ○ ● ○ ○ ○ ○ ○ ○ ○ ○ ○

74-90-8 Hydrogen cyanide (& 

cyanide compounds) ● ● ● ● ○ ○ ● ● ● ○ ○ ● ○ ○ ○ ● ●

7664-39-3 Hydrogen fluoride ○ ○ ○ 

(continued) 
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Table 1-1. Summary of Pollutants and Emission Sources Inclusion 

in a Petroleum Refinery’s Emission Inventory (continued) 

CAS 

Number 

or Pollutant 

Code Substance 

Equipment Leaks Storage Tanks Stationary Combustion 

Process Vents 

Catalytic Cracking Unit Fluid Coking Unit Delayed Coking Unit Catalytic Reforming Unit Sulfur Recovery Plants Hydrogen Plant Asphalt Plant Coke Calcining Blowdown Systems Vacuum Systems Flares Wastewater Cooling Towers Product Loading Fugitive Dust Sources Startup/Shutdown Malfunctions 

7723-14-0 Phosphorus ○ ○ ○ 

Other Compounds of Interest 

7664-41-7 Ammonia ○ ○ ○ ● ● ○ ○ ○ 

74-84-0 Ethane ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○

7783-06-4 Hydrogen sulfide ● ○ ○ ○ ○ ● ● ○ ○ ○ ● ○ ○ ○

7440-39-3 Barium ○ ○ ○ ○ 

7440-50-8 Copper ○ ○ ○ ○ 

7439-98-7 Molybdenum ○ ○ ○ ○ 

7440-62-2 Vanadium ○ ● ● ○ 

7440-66-6 Zinc ○ ○ ○ ○ 

● Designates compound/source pairings for which emission estimates should be developed. 

○ Designates compound/source pairings for which emission estimates may be developed depending on the available data. 

POM Designates compounds that meet the HAP definition of polycyclic organic matter (POM). 

j

 The listed HAP is 2,3,7,8-Tetrachlorodibenzo-p-dioxin (2378-TCDD); other dioxin isomers are listed because they can be 

used to calculate a 2378 TCDD toxicity equivalence. Abbreviations used in the table are as follows: 4D 2378 = 2,3,7,8-

Tetrachlorodibenzo-p-dioxin; 5D 12378 = 1,2,3,7,8-Pentachlorodibenzo-p-dioxin; 6D 123478 = 1,2,3,4,7,8-

Hexachlorodibenzo-p-dioxin; 6D 123678 = 1,2,3,6,7,8-Hexachlorodibenzo-p-dioxin; 6D 123789 = 1,2,3,7,8,9-

Hexachlorodibenzo-p-dioxin; 7D 1234678 = 1,2,3,4,6,7,8-Heptachlorodibenzo-p-dioxin; 8D = Octachlorodibenzo-p-dioxin. k

 The listed HAP is dibenzofurans. Abbreviations used in the table are as follows: 4F 2378 = 2,3,7,8-Tetrachlorodibenzofuran; 

5F 12378 = 1,2,3,7,8-Pentachlorodibenzofuran; 5F 23478 = 2,3,4,7,8-Pentachlorodibenzofuran; 6F 123478 = 1,2,3,4,7,8-

Hexachlorodibenzofuran; 6F 123678 = 1,2,3,6,7,8-Hexachlorodibenzofuran; 6F 123789 = 1,2,3,7,8,9-

Hexachlorodibenzofuran; 6F 234678 = 2,3,4,6,7,8-Hexachlorodibenzofuran; 7F 1234678 = 1,2,3,4,6,7,8-

Heptachlorodibenzofuran; 7F 1234789 = 1,2,3,4,7,8,9-Heptachlorodibenzofuran; 8F = Octachlorodibenzofuran 

Carbon dioxide, methane (CH4), and nitrous oxide are GHGs expected to be emitted from petroleum 

refineries, but are not listed in this table. The Mandatory Greenhouse Gas Emissions Reporting Rule (74 

FR 56260) requires detailed GHG emission reporting from a variety of industry sectors and emission 

sources, including petroleum refineries and stationary combustion sources (40 Code of Federal 

Regulations [CFR] Part 98, Subparts Y and C, respectively). Consequently, this Refinery Emissions 

Protocol document focuses primarily on criteria and toxic air pollutants (i.e., the pollutants listed in 

Table 1-1). Emission estimates for GHG will be calculated and reported according to the methodologies 

and requirements in the GHG reporting rule and are not required to be reported as part of the refinery 

ICR. Note that the “tiers” used in 40 CFR Part 98 Subpart C are listed in opposite order from the “ranks” 

used in this Refinery Emissions Protocol document. That is, the Tier 4 method for stationary combustion 

sources is equivalent to Methodology Rank 1 for combustion sources in this protocol document; the 

Tier 3 method is equivalent to Methodology Rank 2, and so on. 
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While Table 1-1 is intended to provide a comprehensive list of pollutants for each emission source for 

which emission estimates should be provided, there may be pollutants released from some sources for 

which we have little or no information. If there is credible information that emissions of other pollutants 

are released from a given emission source (e.g., from a source test that was conducted on a particular 

process unit), then emission estimates for these additional pollutants should also be provided for that 

process unit, even if Table 1-1 does not include a bullet for that pollutant/emission source combination. 

Again, no new sampling or analysis is required to provide these estimates; available data, supplemented 

with engineering analyses, may be used to develop these estimates. 

1.2 Data Quality 

The consistent use of standardized methods and procedures is essential in the compilation of reliable 

emission inventories. Quality assurance (QA) and quality control (QC) of an emission inventory are 

accomplished through a set of procedures that ensure the quality and reliability of data collection and 

analysis. These procedures include the use of appropriate emission estimation techniques, applicable and 

reasonable assumptions, accuracy/logic checks of computer models, and checks of calculations and data 

reliability. Depending upon the technical approach used to estimate emissions, a checklist with all of the 

particular data needs should be prepared to verify that each piece of information is used accurately and 

appropriately. 

Appropriate metadata (data about the data) should be maintained to assist data users with assessing the 

accuracy of the reported emissions. QA/QC and other metadata records should also be maintained to 

allow verification of the reported emissions, although this information does not need to be reported unless 

specifically requested. For measured emissions, these metadata include manufacturer’s design 

specifications for accuracy, initial calibrations, periodic calibration checks, and other QA/QC procedures 

used to ensure the accuracy of the measurement device(s). For source tests used to develop site-specific 

emission factors, the metadata include results of field and laboratory blanks, duplicate analyses, method 

detection limits, isokinetic and cyclonic flow checks (if applicable), and key process operating data (e.g., 

throughput, temperature, material processed). For some pollutants, there may be different methods by 

which the emissions can be determined. For example, VOC emissions may be determined using a “total 

organics” method (e.g., using EPA Method 25, 25A through 25E, or 305) and subtracting any non-VOCs 

present or by speciating individual VOCs and summing the emissions of these compounds to determine 

the overall VOC emissions. When reporting VOC emissions, therefore, it should be clearly indicated how 

the emissions were determined. If the emissions are determined as TOC or from a TOC measurement, it 

must be indicated how the emission are being reported, i.e., “as methane” (or “as” whatever compound 

was used to calibrate the total organic analyzer). These metadata assist users of the inventory data and 

help to ensure that the inventory data are correctly used when performing subsequent analyses. 

1.3 Calculations and Significant Digits 

The methodology ranking presented in this Refinery Emissions Protocol document is designed to 

highlight and promote those methods that are expected to yield the most accurate emission data. We 

recognize that the Methodology Rank 5 methodologies may only provide emission estimates that are 

within a factor of 2 or 3 from the actual emission rate. Nonetheless, the emission factors presented in this 

document are generally presented with two significant digits. The two significant digits should not be 

construed as an expectation that these emission factors are more accurate. The emission factors are 

provided with two significant digits because it is recommended that all calculations be performed carrying 

at least one additional significant digit to minimize round-off errors. The emissions calculated using 

default emission factors may be rounded to one significant digit when reporting the emissions, but at least 

two significant digits should be carried in the calculations. For methodologies that may have uncertainties 

in the range of ±10 percent, at least three significant digits should be carried when performing the 

calculations, even though the final emission estimate may only warrant two significant digits. 
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2. Equipment Leaks 

Equipment leaks are small emission sources that occur throughout the process area of the refinery from 

various equipment components and connections that develop leaks that allow process fluids to escape into 

the atmosphere. Leaks are typically identified using EPA Method 21 (via an organic vapor analyzer 

[OVA]) or using optical leak imaging techniques; other remote sensing techniques can also be used to 

identify leaks. Although direct measurement methods provide the most accurate means of quantifying 

equipment leak emissions, few, if any, refineries have or will implement direct measurement of 

equipment leak emissions. Instead, mass emissions for several types of equipment can be estimated using 

correlation equations that relate mass emissions to leak concentrations that are obtained using an OVA. In 

the absence of concentration measurements, mass emissions can also be estimated using the number of 

equipment components and emission factors. Typically, these procedures estimate either total organic 

compound (TOC) or non-methane organic compound mass emissions. To estimate either total VOC or 

constituent-specific emissions, the process streams being monitored must be characterized at least to the 

point of identifying the typical VOC concentration. 

The most common optical leak imaging technique at this time uses passive infrared spectral imaging at a 

wavelength that is strongly absorbed by the gas of interest to produce a real-time video image of the 

emission plume. Although this technology is very useful for quickly and easily identifying the presence of 

leaks, particularly large leaks, it has not yet been developed to the point of being able to quantify 

emissions. Therefore, it must be combined with other techniques as described below to quantify 

emissions. Other remote sensing techniques include Differential Absorption Light Detection and Ranging 

(LIDAR) and Solar Occultation Flux. These techniques measure either the volumetric or mass 

concentrations of a compound or mixture of compounds in a vertical cut through a plume. Combining 

these data with wind speed can be used to estimate mass flux. However, these remote sensing techniques 

are not yet approved by EPA as a method of quantifying emissions from equipment leaks or any other 

sources. Furthermore, because the measurement is conducted some distance downwind from a source, the 

techniques alone are not practical for identifying specific leaking equipment components. When 

appropriate, we will update this document to include methodologies for any optical leak imaging or other 

remote sensing techniques that develop to the point of being able to quantify equipment leak emissions. 

Table 2-1 summarizes the hierarchy of equipment leak emission estimation techniques. The methods are 

ranked in terms of anticipated accuracy. Within a given measurement method (or rank), there may be 

alternative methods for determining the constituent-specific emissions; these compositional analysis 

methods are also provided in order of accuracy. It is anticipated that each refinery will use a mixture of 

different methods. For example, Methodology Rank 2a for equipment leaks may be used for certain 

components and Methodology Rank 2b for equipment leaks may be used for other components that are 

monitored using Method 21, depending on the availability of equipment-specific or process-specific 

concentration profiles for a given component or group of components. Additionally, Methodology Ranks 

4 or 5 for equipment leaks may be used to estimate emissions from other components that are not 

routinely monitored. 

The remainder of this section provides additional details and guidance regarding the ways to implement 

these methods. Most of the methods outlined in this section are based on the revised equipment leak 

protocol developed specifically for the petroleum refinery industry. For more information regarding the 

way in which the correlations were developed, please refer to EPA’s document, Protocol for Equipment 

Leak Emission Estimates (U.S. EPA, 1995b). 

For heavy liquid leaks (e.g., fuel oil, heavy gas oil, residual fuel oil, bitumen) that create a pool or puddle 

of liquid, emissions from the accumulated liquid pool should be estimated using the methods for spills in 

Section 12, Malfunctions, of this Refinery Emissions Protocol document in addition to using the methods 
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presented in this section to estimate the emissions that occur at the leaking component. The spill 

methodology is needed in these cases for several reasons. First, for some refinery heavy liquids, the low 

volatility of heavy liquids will result in a relatively low OVA reading using EPA Method 21, even with 

large visible leaks, so that the equipment leak methodologies are expected to understate the potential 

emissions from the pooled material. Second, emissions from the pooled material will be dominated by the 

more volatile components of the heavy liquid, and the spill methodology will more accurately assess the 

speciated emissions from the pooled material. Finally, the spill methodology will better account for the 

dimensions and duration of the liquid pool, which can be affected by the clean-up measures used. 

Table 2-1. Summary of Equipment Leak Emission Estimates 

Rank Measurement Method 

Correlation Equations 

or Emission Factor Compositional Analysis Dataa

1 Direct measurement (high-volume 

sampler or bagging) 

Not necessary Speciation of collected gas samples 

2 EPA Method 21 Correlation equation a) Process-specific, equipmentspecific concentrations 

b) Process-specific average 

concentrations 

c) Refinery average stream 

concentrations 

3 EPA Method 21 Default screening 

ranges factors 

4 No monitoring; facility-specific 

component counts 

Default average 

emission factors 

a) Process-specific, service-specific 

concentrations 

b) Process-specific average 

concentrations 

c) Refinery average stream 

concentrations 

d) Default process compositions 

5 No monitoring; default model 

process component counts 

Default average 

emission factors 

a

 The letters represent ranking sublevels. For example, rank 2a consists of using the correlation equation to 

estimate total VOC emissions and using process-specific and equipment-specific process fluid concentration 

data to estimate speciated emissions. 

2.1 Methodology Rank 1 for Equipment Leaks 

There are two primary quantitative leak measurement methods: the bagging method and high-volume 

sampling. Typically, EPA Method 21 would be used to initially screen and identify leaking components, 

and then one of these methods would be used to quantify the mass emission rate of the leak. Direct leak 

rate measurement, using either of these techniques, is accurate within ±15 percent (U.S. EPA, 2003). 

In the bagging method, the leaking component or leak opening is enclosed in a “bag” or tent. An inert 

carrier gas (e.g., nitrogen) is conveyed through the bag at a known flow rate. Once the carrier gas attains 

equilibrium, a gas sample is collected from the bag, and the TOC concentration of the sample is 

measured. That collected gas can also be analyzed for individual compound concentrations. The mass 

emission rate is calculated from the measured concentrations of the bag sample and the flow rate of the 

carrier gas. Although bagging techniques are useful for the direct measurement of larger leaks, bagging 

may not be possible for equipment components that are inaccessible, unusually shaped, or very large, and 

it is a relatively slow process (i.e., only two or three samples per hour). 

High-volume samplers are essentially vacuums that capture all of the emissions from a leaking 

component to accurately quantify leak emission rates. Leak emissions and a large-volume sample of the 

air around the leaking component are pulled into the instrument through a vacuum sampling hose. Highvolume samplers are equipped with dual hydrocarbon detectors, which measure the concentration of 

hydrocarbon gas in the captured sample and the concentration of ambient hydrocarbon gas. Sample 
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measurements are corrected for the ambient hydrocarbon concentration, and a mass leak rate is calculated 

by multiplying the flow rate of the measured sample by the difference between the ambient gas 

concentration and the gas concentration in the measured sample. Chemical speciation of the leak, using 

vacuum canisters or similar methods, can be used to apportion the TOC emission rate to individual 

constituents. High-volume samplers measure leak rates up to 0.23 cubic meters per minute (m3

/min), 

which is a rate equivalent to 330 cubic meters per day (m3/day), and can be used to quantify 10 to 20 

sources per hour. Leak rates greater than 0.23 m3

/min must be measured using bagging techniques (U.S. 

EPA, 2003). 

While bagging or high-volume sampling are more accurate than other equipment leak emission estimate 

methods, they are time consuming and impractical for routine screening of the large number of equipment 

components present at a refinery. However, some directed inspection and maintenance programs use, for 

example, optical imaging techniques to identify leaking components and then use high-volume sampling 

to quantitate the limited number of leaks identified. While these methods are more common at oil and gas 

production operations, they could also be applied at some refineries for certain sources. As the emission 

rate measured by the high-volume sampler (or bagging method) will be more accurate for that specific 

leak than emission estimates developed using any of the lower-ranked methodologies, the high-volume 

sampling (or bagging) results should be used for that specific leak if high-volume sampling (or bagging) 

is conducted. 

2.2 Methodology Rank 2 for Equipment Leaks 

Most leak detection and repair (LDAR) programs require periodic monitoring using EPA Method 21 to 

identify leaking components. The preferred methodology for estimating equipment leak emission rates 

directly from EPA Method 21 data (i.e., Methodology Rank 2 for equipment leaks) is to use the screening 

value correlations in the right column of Table 2-2 (U.S. EPA, 1995b) for each individual component as 

screened via EPA Method 21. When a screening value of zero is registered, the default zero value in the 

second column in Table 2-2 is used to estimate TOC emissions. If the monitoring instrument measures 

concentrations only up to 10,000 parts per million by volume (ppmv) or 100,000 ppmv, then the 

applicable values for pegged emission rates in Table 2-2 are used to estimate emissions. Table 2-2

includes screening value correlations for both the petroleum industry (applicable for petroleum refinery 

operations, marketing terminals, and oil and gas production) and the synthetic organic chemical 

manufacturing industry (SOCMI). Generally, most petroleum refineries will use the petroleum industry 

correlations; however, the SOCMI correlations are provided here for convenience because some refineries 

may also have chemical manufacturing processes that must be included in the facility’s emission 

inventory. 

Many refineries or monitoring specialists use software programs that directly record the TOC reading (or 

screening value) for each component. Many of these software programs will directly calculate the TOC 

emissions for each component using the screening value correlations and will even calculate componentspecific emission rates when composition data are entered for the components. The TOC rates calculated 

by the correlation equation (and the default zero and pegged emission rate values) include non-VOC 

organic compounds, primarily methane and ethane. The uncertainty of the correlations for any single 

measurement may be as much as a factor of 3 higher or a factor of 10 lower than the actual emissions for 

that component, but when summed over thousands of components, the uncertainty in the cumulative total 

emissions is expected to be much less. For example, based on Monte Carlo simulations of 100 leaking 

components and using an uncertainty of plus or minus a factor of 10, the uncertainty in the cumulative 

emissions is approximately plus or minus a factor of 1.4. The advantage of Methodology Rank 2 for 

equipment leaks is that it is not based on a presupposed distribution of equipment leaks, as are the lower 

ranked methodologies. Consequently, Methodology Rank 2 for equipment leaks is much more accurate 

than any of the lower ranked equipment leak emission estimation methods. 
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Table 2-2. Equipment Leak Rate for Petroleum and SOCMI Equipment Componentsa

Equipment Type 

(All Services) 

Default Zero 

Emission Rate 

(kg/hr/source) 

Pegged Emission Rates 

(kg/hr/source) Correlation Equationb

10,000 ppmv 100,000 ppmv (kg/hr/source) 

Leak Rates for Petroleum Industry (Refinery, Marketing Terminals, and Oil and Gas Production) 

Valve 7.8E-06 0.064 0.14 2.29E-06×SV0.746

Pump 2.4E-05 0.074 0.16 5.03E-05×SV0.610

Otherc 4.0E-06 0.073 0.11 1.36E-05×SV0.589

Connector 7.5E-06 0.028 0.030 1.53E-06×SV0.735

Flange 3.1E-07 0.085 0.084 4.61E-06×SV0.703

Open-ended line 2.0E-06 0.030 0.079 2.20E-06×SV0.704

Leak Rates for Synthetic Organic Chemical Manufacturing Industry (SOCMI) 

Gas valve 6.6E-07 0.024 0.11 1.87E-06×SV0.873

Light liquid valve 4.9E-07 0.036 0.15 6.41E-06×SV0.797

Light liquid pumpd 7.5E-06 0.14 0.62 1.90E-05×SV0.824

Connector 6.1E-07 0.044 0.22 3.05E-06×SV0.885

Note: kg/hr/source = kilograms TOC per hour per source 

a

 Data reported in U.S. EPA, 1995b. 

b

 SV is the screening value (SV, ppmv) measured by the monitoring device. 

c

 The “other” equipment type was developed from instruments, loading arms, pressure relief devices, stuffing 

boxes, vents, compressors, dump lever arms, diaphragms, drains, hatches, meters, and polished rods. This 

“other” equipment type should be applied to any equipment other than connectors, flanges, open-ended lines, 

pumps, or valves. d

 The light liquid pump factors can also be applied to compressors, pressure relief valves, agitators, and heavy 

liquid pumps. 

When an optical gas imaging camera is used to identify leaks, the emissions can be quantified under 

Methodology Rank 2 (or Methodology Rank 1 for certain components) only if both of the following 

conditions are met: (1) the equipment is monitored in accordance with the procedures in §63.11(e), and 

(2) all leaks identified by the camera are monitored before repair using Method 21 or are measured using 

high-volume sampling or bagging methods. For equipment found to be leaking when monitoring with the 

camera, either the subsequent Method 21 screening values in the applicable correlation equation should 

be used to estimate the emissions (Methodology Rank 2) or the leak rake rates measured via the highvolume sampling or bagging method (Methodology Rank 1) should be used, as applicable. For all 

equipment not found to be leaking when monitoring with the camera, emissions should be estimated 

using the screening values obtained when conducting the annual Method 21 monitoring required by 

§63.11(d)(7) in the applicable correlation equations. 
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2.2.1 Speciating Equipment Leak Emissions 

In developing constituent-specific emission estimates, the composition of the process stream in contact 

with the equipment is used to estimate the speciated equipment leak emissions. To the extent that 

compositional data are available for individual process streams, each equipment component associated 

with that process stream should be tagged with the average composition of that process stream 

(Methodology Rank 2a for equipment leaks). Although an ideal situation would be if chemical speciation 

data were available for each equipment component (i.e., each process stream associated with each 

equipment component), in many cases, this level of detail may not be available. Alternatively, average 

compositional data may be determined for all streams in a specific process unit, for groups of streams in 

different portions of a process unit, or for groups of streams in a particular service type in a process unit. 

Under this approach, all equipment associated with the applicable group of streams would be tagged with 

the same concentration profile (Methodology Rank 2b for equipment leaks). For example, an average 

composition could be determined for all gas streams, all light liquid streams, and all heavy liquid streams 

at a given refinery process unit (resulting in three composition profiles per unit). Alternatively, an overall 

average composition could be determined for all streams (regardless of the type of service) for that 

process unit (resulting in one composition profile per unit). As a last resort, a single, overall average 

Example 2-1: Calculation for Methodology Rank 2 for Equipment Leaks 

A refinery catalytic reforming unit (CRU) operating 8,000 hours per year (hr/yr) has 600 

valves. To keep the example simple, assume Method 21 monitoring registers the screening 

value readings in the following table, and assume the average weight percents of methane and 

ethane in all streams are known or estimated to be equal to 3 percent and 1 percent of the 

TOC, respectively. Also assume the TOC content of each stream is 100 percent. Using 

Methodology Rank 2b for equipment leaks (correlation approach), what is the cumulative 

hourly VOC emission rate from the valves in this process unit at the time the monitoring is 

conducted? 

To calculate the emissions, the default zero value for valves on Table 2-2 (7.8E-06) is used to 

estimate the TOC emissions from the 580 valves with a screening value of 0 ppmv. The 

pegged emission rate for valves in Table 2-2 (0.140) is used to estimate the TOC emission 

rate for the two valves with pegged readings. The correlation equation for valves in Table 2-2

(2.29E-06 x SV^0.746) is used to estimate the emissions for each of the valves with a 

measured screening value. In each case, the calculated TOC emissions are multiplied by (100-

4)/100 to calculate the VOC emissions. 

Number of Valves 

Method 21 Screening 

Value, ppmv 

Emissions, kg/hr 

TOC VOC 

580 0 0.00452 0.00434 

5 200 0.00012 0.00011 

5 400 0.00020 0.00019 

2 1,500 0.00054 0.00051 

2 7,000 0.00169 0.00162 

2 20,000 0.00370 0.00355 

2 50,000 0.00733 0.00704 

2 Pegged at 100,000 0.28000 0.26880 

Total 0.30 0.29 
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process stream composition can be estimated on a refinery-wide basis (e.g., one concentration profile for 

the entire refinery, which is Methodology Rank 2c for equipment leaks). Methodology Rank 2c for 

equipment leak emissions is very easy to implement in that the TOC emissions can be aggregated for all 

components first, and then the chemical-specific emissions can be calculated from the cumulative TOC 

emissions. However, this method greatly reduces the accuracy of the chemical-specific emission rates. 

With the automated software programs that are now available for logging equipment leak readings and 

calculating equipment leak emissions, most refineries should be able to implement Methodology Rank 2a 

or 2b for equipment leaks. 

The correlation equations for equipment leaks provided in Table 2-2 provide emissions in terms of TOC 

(including methane and ethane). To calculate the emission rate for VOC (i.e., to exclude methane and 

ethane), use Equation 2-1. 

 EVOC = ETOC × (WFVOC/WFTOC) (Eq. 2-1) 

where: 

 EVOC = Emission rate of VOC for a specific type of equipment (kilograms per year [kg/yr]) 

 ETOC = Emission rate of TOC for a specific type of equipment (kg/yr) 

 WFVOC = Average weight fraction of VOC in the stream (typically TOC minus methane and 

ethane) 

 WFTOC = Average weight fraction of TOC in the stream. 

Table 1-1 in Section 1, Introduction, lists the specific organic compounds that should be included in an 

inventory of equipment leak emissions. Either of the following equations (Equation 2-2a or Equation 

2-2b) is used to speciate emissions for specific organic compounds from a single equipment piece: 

 Ei = ETOC × (WFi/WFTOC) (Eq. 2-2a) 

 Ei = EVOC × (WFi/WFVOC) (Eq. 2-2b) 

where: 

 Ei = Mass emissions of organic chemical “i” from the equipment (kg/yr) 

 WFi = Concentration of organic chemical “i” in the equipment (weight fraction). 
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2.2.2 Calculating Hourly and Annual Equipment Leak Emissions 

The emissions estimated based on EPA Method 21 measurement data (i.e., Methodology Rank 2 for 

equipment leaks) represent the emission rate at the time when the measurements were made (i.e., hourly 

emission estimates). Thus, the direct emission rate calculated based on the monitored screening values 

should be used for the hourly emission estimate. If the components are monitored multiple times per year, 

the hourly emissions for each process unit should be calculated for each monitoring period (as the 

summation of the emissions of all components for that process unit), and the monitoring period resulting 

in the highest overall emission rate is to be reported as the hourly emission rate for that unit. There may 

be components that are monitored at different frequencies; for example, pumps may be monitored 

monthly, while valves are monitored either quarterly or semi-annually. In general, the hourly emissions 

for the process unit should only be calculated for the periods where a significant number of the 

components are monitored (in the example, quarterly or semi-annually). One should not take the highest 

hourly emission rate for each individual component, regardless of when it was monitored during the year, 

and then sum the maximum value for the individual components because this will tend to overstate the 

actual hourly emission rate from the process unit. 

The first time an LDAR program is implemented, the emission estimates from the component screening 

measurements should be used as the emission rate for the facility (or an individual component or set of 

components) for all periods prior to the screening measurements (i.e., the portions of the inventory year 

prior to the screening measurements). However, most equipment components at a refinery are expected to 

be monitored for leaks on a routine basis (i.e., monthly, quarterly, or semiannually) as part of an ongoing 

LDAR program. Leaks greater than a certain threshold are required to be repaired within certain time 

frames (although many LDAR programs allow some repairs to be delayed). After repairs are made, the 

Example 2-2: Calculation for Speciating Equipment Leak Emissions 

For Example 2-1, the measured composition of the process stream associated with one of the 

valves (Methodology Rank 2a) for which a screening value of 7,000 ppmv was obtained is: 

Hexane 10 wt% 

Toluene 8 wt% 

Benzene 2 wt% 

Other volatile organic compounds (VOCs) 60 wt% 

Methane and ethane 4 wt% 

Nitrogen 10 wt% 

Water 5 wt% 

Hydrogen 1 wt% 

The TOC weight fraction is calculated as the sum of all of the organic compounds. The VOC 

weight fraction is the sum of all of the organic compounds, minus methane and ethane, as 

shown in the following equation: 

WFVOC = (%Hexane + %Toluene + %Benzene +% Other VOC)/100% 

= (10 + 8 + 2 + 60)/100 = 0.80 

From Example 2-1, the valve’s VOC emission rate was 0.81 grams per hour (g/hr). 

Equation 2-1 is used to attribute these emissions to individual components as follows: 

EHexane = 0.81 × (0.1/0.8) = 0.10 g/hr 

EToluene = 0.81 × (0.08/0.8) = 0.08 g/hr 

EBenzene = 0.81 × (0.02/0.8) = 0.02 g/hr 

EOtherVOC = 0.81 × (0.60/0.8) = 0.61 g/hr 
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repaired components should be re-screened to verify that the leak has been repaired and to provide a new 

starting emission rate for that component. During the next routine monitoring period, new screening 

values will be determined for each component, providing new instantaneous emission rate estimates for 

each component. The variations in component emissions during the year need to be accounted for when 

developing annual emission estimates for equipment components that are routinely monitored. Figure 2-1

illustrates the three acceptable methods for estimating annual emissions from routinely (monthly, 

quarterly, semiannually) monitored equipment components. 

Figure 2-1. Illustration of alternative methods to determine equipment leak emissions 

from routine monitoring data. 

The mid-period method assumes that the initial reading represents the emission rate for the first half of 

the period between monitoring events and that the subsequent reading represents the emission rate for the 

second half of the period between monitoring events. When a leak is detected for subsequent repair, the 

“leak” monitor reading is used from the time the leak is detected to the time it is repaired (i.e., rescreened). The modified trapezoid method assumes that the mass leak rate changes linearly between any 

two monitoring points, except for periods between leak detection and repair; the leak monitor reading is 

used from the time the leak is detected to the time it is repaired (i.e., re-screened). The average period 

method uses the arithmetic average emission rate of two adjacent instantaneous emission rate estimates 
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(except for periods between leak detection and repair) for the emission rates between the measurement 

periods. As in the mid-period and modified trapezoid method, the average period method uses the leak 

monitor reading from the time the leak is detected to the time it is repaired (i.e., re-screened). In all of 

these alternatives, it is important that the emission rate be determined for each component and each 

monitoring event before extrapolating the emissions to the intervening periods. It is invalid to average the 

monitored screening values first and then to calculate the emission rate based on the average screening 

value. 

Mathematically, the calculated emissions for periods wholly within the inventory year will be identical 

regardless of the alternative selected. Provided that one can elect the “inventory year period” to start and 

end with a monitoring event, then the method selected is immaterial. The only difference in the annual 

emissions determined using the three alternative methods for routinely monitored components will occur 

if emissions must be determined for a specific time period (e.g., a calendar year), and the emissions 

determined for an intervening interval (between monitoring events at the end of one year and start of the 

next year) must be parsed between the two years. While there can be differences in the annual emissions 

calculated using these different methods for a particular component, these differences will tend to cancel 

out when emissions are summed over a large number of components. Therefore, it is only important that 

there is consistency in the application of the selected method (i.e., all components use the mid-period 

method or all components use the modified trapezoid method or all components use the average period 

method). 

If the equipment is taken out of service (e.g., no process fluid is in the piping at the location of the 

specific component), the emission rate for that component can be assumed to be zero for the time period 

the equipment in out of service. If the process unit is not operating, but fluid remains in the components, 

then no correction for operating hours should be made. There can be some differences in the emissions 

calculated for the operating periods between monitoring intervals when the components are out of service, 

but these differences are expected to be small. Again, consistency in the application of the selected 

method is of key importance. 

When emission inventories are required for a set calendar year, there are also some practical matters to 

consider when selecting an annual estimation method for components, especially when components are 

monitored semiannually or less often. The midpoint method has the advantage of not relying on the 

subsequent year’s first semiannual monitoring if the last semiannual monitoring event for the inventory 

year occurred in October or later. If the last semiannual monitoring event for the inventory year occurred 

prior to October, then the subsequent year’s first semiannual monitoring would likely occur in March or 

earlier, so that the inventory could be developed in a timely fashion, even if the subsequent year’s 

monitoring data are needed to complete the inventory for the current year. Similarly, for annual 

component monitoring, the midpoint method would not require the subsequent year’s monitoring results 

if monitoring occurred in July or later. On the other hand, the application of either the modified trapezoid 

method or the average period method requires the subsequent year’s monitoring data, regardless of when 

that monitoring event occurs; the modified trapezoid method is further complicated in that interpolation is 

required to correctly account for emissions between two inventory years. If allowed, an “equipment leak 

year” (like a fiscal year) could be established based on the typical timing of the monitoring events, so that 

the emissions for that equipment leak year can be determined based entirely on whole monitoring periods. 
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2.3 Methodology Rank 3 for Equipment Leaks 

In some older LDAR programs, the only information that is recorded is whether a leak was found. For 

these LDAR programs, leaks were defined as screening value readings greater than 10,000 ppmv. In these 

cases, generally the available data are the number of components of each type at the plant and the number 

of components of each type found with TOC readings less than 10,000 ppmv and the number of 

components of each type with TOC readings greater than or equal to 10,000 ppmv. Methodology Rank 3 

for equipment leaks estimates the emission rate using these data and the screening ranges emission factors 

in AP-42 (U.S. EPA, 1995b). Table 2-3 provides the screening ranges emission factors for refinery and 

SOCMI sources; see AP-42 for additional screening ranges emission factors for marketing terminals or oil 

and gas production operations if these sources are also part of the facility. If the number of components 

and the number of leakers are recorded by process, then this provides a more accurate method for using 

Example 2-3: Calculation for Annual Emissions Using the Midpoint Method 

The following monitoring data for a pump were recorded (Columns 1 and 2). The correlation 

equation from Table 2-2 for pumps is used (i.e., 5.03E-05×SV0.610) to calculate the emissions 

rate in Column 3 when the OVA reading is greater than zero, and the default zero rate is used 

when the OVA reading is zero. The hours between intervals were calculated; half of the hours 

were assigned to the first reading, and half were assigned to the second reading, except for 

periods before repair, which were assigned the “leak” emission rate. 

1 

Date and Time 

2 

OVA Reading 

(ppm) 

3 

TOC Emission 

Rate 

(kg/hr) 

4 

Hoursa

5 

TOC Emissions

(kg/period) 

January 2, 8:00 a.m. 200 1.27E-3 32+372 0.51 

February 2, 8:00 a.m. 300 1.63E-3 372+336 1.15 

March 2, 8:00 a.m. 280 1.56E-3 336+372 1.10 

April 2, 8:00 a.m. 22,000 2.24E-2 372+74 9.99 

April 5, 10:00 a.m.b 150 1.07E-3 323 0.35 

May 2, 8:00 a.m. 140 1.02E-3 323+372 0.71 

June 2, 8:00 a.m. 200 1.27E-3 372+360 0.93 

July 2, 8:00 a.m. 180 1.19E-3 360+372 0.87 

August 2, 8:00 a.m. 500 2.23E-3 372+372 1.66 

September 2, 8:00 a.m. 45,000 3.47E-2 372+241 21.27 

September 12, 9:00 a.m.b 0 2.4E-5 239.5 0.006 

October 2, 8:00 a.m. 0 2.4E-5 239.5+372 0.015 

November 2, 8:00 a.m. 0 2.4E-5 372+360 0.018 

December 2, 8:00 a.m. 200 1.27E-3 360+372 0.93 

January 2, 8:00 a.m. 250 1.46E-3 372-32 0.50 

Annual Totals 8,760 40.0 kg/yr 

a

 Each emission rate applies over half of the hours since the previous screening and over half of the hours 

until the next screening. For example, the results from the July 2 measurement apply to half of the hours 

since the June 2 measurement and to half of the hours before the next measurement on August 2. The 

July 2 measurements occur 30 days (720 hours) after the June 2 measurement and 31 days (744 hours) 

before the August 2 measurements. Therefore, the July 2 results apply to 732 hours during the year 

(720/2 + 744/2 = 732). b

 Indicates special Method 21 measurement reading to verify repair. 
Version 2.1.1 

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process-specific compositional data to estimate constituent-specific emission rates (Methodology Ranks 

3a and 3b). Alternatively, the average percentage of leakers facility-wide can be used, and these data can 

be coupled with process-specific component counts to estimate emissions by process (Methodology 

Rank 3c). 

Table 2-3. Screening Ranges Emission Factorsa

Equipment type Service 

Refinery Factorsb SOCMI Factorsc

≥10,000 ppmv 

emission 

factor (kg/hr/ 

source)b

<10,000 ppmv 

emission 

factor (kg/hr/ 

source)b

≥10,000 ppmv 

emission 

factor (kg/hr/ 

source)c

<10,000 ppmv 

emission 

factor (kg/hr/ 

source)c

Valves Gas 0.2626 0.0006 0.0782 0.000131 

 Light liquid 0.0852 0.0017 0.0892 0.000165 

 Heavy liquid 0.00023 0.00023 0.00023 0.00023 

Pump and agitator 

seals 

Light liquid 0.437 0.0120 0.243 0.00187 

Heavy liquid 0.3885 0.0135 0.216 0.0210 

Compressor seals All 1.608 0.0894 1.608 0.0894 

Pressure relief 

valves 

All 1.691 0.0447 1.691 0.0447 

Connectors All 0.0375 0.00006 0.113 0.000081 

Open-ended lines All 0.01195 0.00150 0.01195 0.00150 

a

 Data reported in U.S. EPA, 1995b. 

b

 These factors are for non-methane organic compound emissions. 

c

 These factors are for total organic compound emissions.

The uncertainty of the leak rates calculated using the screening ranges emission factors for any single 

measurement may be a factor of 10 or more. Although this methodology is intended to account for 

reduced emissions gained by an LDAR program, the underlying default leak rates are based on the 

distribution of leaks prior to the implementation of an LDAR program. This method is expected to be 

biased high for facilities that have implemented an LDAR program, especially an LDAR program with 

leak action levels less than 10,000 ppmv. First, the implementation of any LDAR program is expected to 

alter not only the prevalence of leaks, but the relative magnitude of leaks above the action level (i.e., the 

average component leak rate for components with screening values of 10,000 ppmv or more). 

Furthermore, if an LDAR program uses a 1,000 ppmv leak action level, the relative magnitude and 

number of leaks with screening values between 1,000 ppmv and 10,000 ppmv is expected to be much less 

than for facilities that use a 10,000 ppmv screening level or do not have an LDAR program. The 

distribution of leaks is also affected by the monitoring frequency, so components that are monitored 

quarterly are expected to have a different leak frequency distribution than components that are monitored 

annually. As such, the emissions estimated using Methodology Rank 3 for equipment leaks is expected to 

be an upper-range emission estimate of equipment leak emissions. The accuracy of this method is 

dependent on the level of LDAR program used; the more frequent the monitoring and the lower the leak 

action level is, the more likely this method will be to significantly overestimate emissions (by as much as 

a factor of 10 to 50, based on data from Lev-On et al. [2007]). 

The leak/no-leak factors presented by Lev-On et al. (2007) were evaluated for facilities that use an optical 

gas imaging camera to identify leaks as a potential Methodology Rank 3 for equipment leaks. However, 

for the same reasons the screening ranges emission factors presented in Table 2-3 are expected to 

overestimate actual emissions for facilities that have implemented a stringent LDAR program, the 

leak/no-leak factors presented by Lev-On et al. (2007) are expected to underestimate the emissions from 
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facilities that only use an optical gas imaging camera. The leak/no-leak factors presented by Lev-On et al. 

(2007) are based on a distribution of leaks for refineries that used quarterly monitoring with a leak 

definition of 1,000 ppmv. Most optical gas imaging cameras have leak detection sensitivities much higher 

than this level. As such, the distribution of leaks by screening range is expected to be much different than 

the baseline distribution used to develop the leak/no-leak factors for optical imaging cameras. Until 

leak/no-leak factors are available for a more representative distribution of leaks, there is no acceptable 

Methodology Rank 3 for quantifying emissions using an optical gas imaging camera. 

2.3.1 Speciating Equipment Leak Emissions 

The refinery screening ranges emission factors are for non-methane organic compound emissions. To 

apply the refinery screening ranges emission factor approach, use Equation 2-3 to calculate the total 

annual TOC emissions per type of equipment for which Methodology Rank 3 is used. Note: Equation 2-3 

should be applied separately to groups of equipment in streams with significantly different methane 

weight fractions. The SOCMI screening ranges emission factors are presented in terms of TOC, so 

Equation 2-3 does not apply to the SOCMI factors. For both refinery and SOCMI screening ranges 

emission factors, use Equations 2-1 and 2-2a or 2-2b (presented previously in Section 2.2.1) to calculate 

the VOC and specific compound emissions, respectively. 

⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

⎥

⎥

⎦

⎤

⎢

⎢

⎣

⎡

×⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

− + ×

⎥

⎥

⎦

⎤

⎢

⎢

⎣

⎡

×⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

− = × L

TOC m

TOC

G L

TOC m

TOC

TOC G N

WF WF

WF

N F

WF WF

WF

E F (Eq. 2-3) 

where: 

 ETOC = Emission rate of TOC for a specific type of equipment (kg/hr) 

 FG = Applicable emission factor for specific type of equipment type with screening values 

greater than or equal to 10,000 ppmv (kg/hr/source) 

 FL = Applicable emission factor for specific type of equipment with screening values less 

than 10,000 ppmv (kg/hr/source) 

 WFTOC = Average weight fraction of TOC in the stream 

 WFm = Average weight fraction of methane in the stream 

 NG = Equipment count (specific equipment type) for sources with screening values greater 

than or equal to 10,000 ppmv 

 NL = Equipment count (specific equipment type) for sources with screening values less than 

10,000 ppmv. 

2.3.2 Calculating Hourly and Annual Equipment Leak Emissions 

Typically, facilities that use Methodology Rank 3 have limited data. The instantaneous emission rate 

measured during a given monitoring event is used directly as the hourly emission rate for the process unit 

at that time. If the facility monitors annually, the instantaneous emission rate calculated for a given 

process or facility is used directly as the hourly emission rate for the process unit. The annual emissions 

for the process unit are calculated using the hourly emission rate and annual operating hours of the 

process equipment as shown in Equation 2-4. If more than one monitoring event occurs during the year, 

the instantaneous (hourly) emission rates calculated for each monitoring period are calculated and the 

highest value is reported for the hourly emissions. The annual emissions are calculated as the average of 

the calculated instantaneous emission rates multiplied by the operating hours of the equipment. 

ETOC,annual = ETOC × H (Eq. 2-4) 
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where: 

 ETOC,annual = Annual emission rate of TOC for a specific type of equipment (kilograms per year 

[kg/yr]) 

 ETOC = Emission rate of TOC for a specific type of equipment (kg/hr) 

 H = Operating hours per year (hr/yr). 

2.4 Methodology Ranks 4 and 5 for Equipment Leaks 

Methodology Ranks 4 and 5 for equipment leaks should be used only for components that are not being 

routinely monitored for leaks. For refineries, this might be processes that have low hazardous air pollutant 

(HAP) and low VOC content, or it might be specific types of components that are either classified as 

unsafe to monitor (e.g., certain pumps and valves) or are not subject to the monitoring requirements (e.g., 

Example 2-4: Calculation for Methodology Rank 3 for Equipment Leaks 

For the valves in the same reforming unit described in Example 2-1, what is the cumulative 

hourly VOC emission rate when Methodology Rank 3 is used? What are the annual VOC 

emissions? Assume that the distribution of valves in gas, light liquid, and heavy liquid service 

is as shown in the table below, and assume that the valves were monitored once during the 

year. 

To calculate hourly TOC emissions for valves in gas service with screening values less than 

10,000 ppmv, use the second half of Equation 2-3. 

 ETOC = [FL × (WFTOC/(WFTOC – WFm)) × NL] 

 = [0.0006 × (100/(100-3)) × 236] 

 = 0.146 kg TOC/hr 

Use the same procedure to calculate emissions for valves in light liquid service and heavy 

liquid service of 0.514 kilograms of TOC per hour (kg TOC/hr) and 0.015 kg TOC/hr, 

respectively. Thus, the total TOC emissions for all valves with screening values less than 

10,000 ppmv are 0.675 kg/hr. Use Equation 2-1 to calculate the VOC emissions from these 

valves. 

 EVOC = ETOC × (WFVOC/WFTOC) 

 = 0.675 × (100-4)/100 

 = 0.648 kg VOC/hr 

Use the same procedure with the first half of Equation 2-3 to estimate TOC emissions of 1.076 

kg/hr from the valves with screening values equal to or greater than 10,000 ppmv, and apply 

Equation 2-1 to calculate VOC emissions of 1.033 kg/hr. Total annual emissions are 

calculated to be 13,400 kg VOC/yr (1.68 kg/hr x 8,000 hr/yr). 

Screening 

Value, 

ppmv 

Number of Valves by Type 

of Service 

Emission Factors, 

kg/hr/source TOC 

Emissions, 

kg/hr 

VOC 

Emissions, 

Gas kg/hr 

Light 

Liquid 

Heavy 

Liquid Gas 

Light 

Liquid 

Heavy 

Liquid 

<10,000 236 293 65 0.0006 0.0017 0.00023 0.675 0.648 

≥10,000 3 3 0 0.2626 0.0852 0.00023 1.076 1.033 

 1.68 
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2-14 

connectors) in the new source performance standards (NSPS) or Petroleum Refinery Maximum 

Achievable Control Technology (MACT) I rules. Facility- or process-specific component counts 

(Methodology Rank 4 for equipment leaks) should be used when these data are available. Methodology 

Rank 4 is preferred over default component counts (Methodology Rank 5 for equipment leaks) because 

these defaults may not account for facility-specific factors (e.g., control of pressure relief valves). 

Default component counts (Methodology Rank 5 for equipment leaks) are dependent on the size of the 

refinery and the process units present. The median (default) equipment component counts for small 

refineries (those less than 50,000 barrels per calendar day [bbl/cd])1

 and large refineries (greater than 

50,000 bbl/cd) as presented in EPA’s document, Locating and Estimating Air Emissions from Sources of 

Benzene (U.S. EPA, 1998a), are presented in Tables 2-4 and 2-5, respectively. 

For both Methodology Ranks 4 and 5 for equipment leaks, default emission factors per component for 

uncontrolled or unmonitored components must be used. It is assumed that these components are not 

monitored because emissions from monitored components should be estimated using a higher ranked 

methodology (Methodology Rank 1, 2, or 3 for equipment leaks). The default emission factor per 

component for uncontrolled or unmonitored components is provided in EPA’s document, Protocol for 

Equipment Leak Emission Estimates (U.S. EPA, 1995b). These emission factors for refinery and SOCMI 

components are summarized in Table 2-6. 

2.4.1 Speciating Equipment Leak Emissions 

The emission factors for refinery components in Table 2-6 were developed to estimate emissions of nonmethane organic compounds (NMOCs). Therefore, to estimate VOC emissions, the emission factor must 

be multiplied by the ratio of the VOC-to-NMOC weight fractions. Additionally, the emission factors 

apply specifically to streams that are 100 percent TOC. To calculate VOC emissions from equipment in 

contact with a stream that contains both organic compounds and other compounds, such as nitrogen or 

water vapor, the emission factor must be multiplied by the TOC weight fraction in the stream. As a result, 

TOC, methane, and ethane weight fractions must be known or estimated in order to calculate the VOC 

emissions as shown in Equation 2-5. 

WF N

WF WF

WF WF WF E FA TOC

TOC methane

TOC ethane methane

VOC × × ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

−

− − = × (Eq. 2-5) 

where: 

 EVOC = Emission rate of VOC from all equipment in the stream of a given equipment type 

(kg/hr) 

 FA = Applicable average non-methane organic compounds emission factor for the 

equipment type (kg/hr/source) 

 WFTOC = Average weight fraction of TOC in the stream 

 WFethane = Average weight fraction of ethane in the stream 

 WFmethane = Average weight fraction of methane in the stream 

 N = Number of pieces of equipment of the applicable equipment type in the stream. 

 

 

1

 Barrels per calendar day is the amount of crude that a refinery can process under usual operating conditions and is 

expressed in terms of actual capacity during a 24-hour period (i.e., actual annual capacity divided by 365 days). The 

other typical capacity measure, barrels per stream day (bbls/sd), is the maximum number of barrels of crude that a 

refinery can process within a 24-hour period when running at full capacity. 
Version 2.1.1 

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2-15 

Table 2-4. Median Equipment Leak Component Counts for Small Model Processesa

Process Unit 

Valves Pumps 

Compressors

Pressure Relief Valves Flanges 

Gas 

Light 

Liquid 

Heavy 

Liquid 

Light 

Liquid 

Heavy 

Liquid Gas 

Light 

Liquid 

Heavy 

Liquid Gas 

Light 

Liquid 

H

Li

Crude distillation 75 251 216 8 8 2 6 6 5 164 555 Alkylation (sulfuric acid) 278 582 34 18 10 1 12 15 4 705 1,296 Alkylation (HF) 102 402 62 13 3 2 12 13 0 300 1,200 Catalytic reforming 138 234 293 8 5 3 5 3 3 345 566 Hydrocracking 300 375 306 12 9 2 9 4 4 1,038 892 Hydrotreating/hydrorefining 100 208 218 5 5 2 5 3 5 290 456 Catalytic cracking 186 375 450 13 14 2 8 8 7 490 943 Thermal cracking (visbreaking) 206 197 0 7 0 0 4 0 0 515 405 Thermal cracking (coking) 148 174 277 9 8 2 7 16 13 260 322 Hydrogen plant 168 41 0 3 0 2 4 2 0 304 78 Asphalt plant 120 334 250 5 8 2 5 10 9 187 476 Product blending 67 205 202 6 11 1 10 6 22 230 398 Sulfur plant 58 96 127 6 6 3 3 88 15 165 240 Vacuum distillation 54 26 84 6 6 2 2 5 2 105 121 Full-range distillation 157 313 118 7 4 2 5 4 6 171 481 Isomerization 270 352 64 9 2 2 7 10 1 432 971 Polymerization 224 563 15 12 0 1 10 5 3 150 450 MEK dewaxing 145 1,208 200 35 39 3 10 14 4 452 1,486 2Other lube oil processes 153 242 201 7 5 2 5 5 5 167 307 a Process component counts as presented in EPA’s document, Locating and Estimating Air Emissions from Sources of Benzene (U.S. EPA, 1998a), for refineries wi

50,000 bbl/cd. 
Version 2.1.1 

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2-16 

Table 2-5. Median Equipment Leak Component Counts for Large Model Processesa

Process Unit 

Valves Pumps 

Compressors

Pressure Relief Valves Flanges 

Gas 

Light 

Liquid 

Heavy 

Liquid 

Light 

Liquid 

Heavy 

Liquid Gas 

Light 

Liquid 

Heavy 

Liquid Gas 

Light 

Liquid 

Hea

Liq

Crude distillation 204 440 498 15 14 2 7 5 12 549 982 1,Alkylation (sulfuric acid) 192 597 0 21 0 2 13 4 0 491 1,328 Alkylation (HF) 104 624 128 13 8 1 9 11 1 330 1,300 Catalytic reforming 310 383 84 12 2 3 8 11 0 653 842 Hydrocracking 290 651 308 22 12 2 10 12 0 418 1,361 Hydrotreating/hydrorefining 224 253 200 7 6 2 9 4 8 439 581 Catalytic cracking 277 282 445 12 12 2 11 9 13 593 747 Thermal cracking (visbreaking) 110 246 130 7 6 1 6 3 15 277 563 Thermal cracking (coking) 190 309 250 12 11 1 8 5 10 627 748 Hydrogen plant 301 58 0 7 360 3 4 139 0 162 148 Asphalt plant 76 43 0 4 0 0 3 7 0 90 90 Product blending 75 419 186 10 10 2 9 16 6 227 664 Sulfur plant 100 125 110 8 3 1 4 4 4 280 460 Vacuum distillation 229 108 447 2 12 1 5 1 4 473 136 1,Full-range distillation 160 561 73 14 2 2 7 8 2 562 1,386 Isomerization 164 300 78 9 5 2 15 5 2 300 540 Polymerization 129 351 82 6 2 0 7 12 28 404 575 MEK dewaxing 419 1,075 130 29 10 4 33 6 18 1,676 3,870 Other lube oil processes 109 188 375 5 16 3 8 6 20 180 187 1,a Process component counts as presented in EPA’s document, Locating and Estimating Air Emissions from Sources of Benzene (U.S. EPA, 1998a), for refineries wi

50,000 bbl/cd. 
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2-17 

Table 2-6. Refinery and SOCMI Average Component Emission Factorsa

Equipment Type Service 

Refinery Emission Factor

(kg/hr/source)b

SOCMI Emission 

Factor 

(kg/hr/source)c

Valves Gas 0.0268 0.00597 

Light liquid 0.0109 0.00403 

Heavy liquid 0.00023 0.00023 

Pump sealsd Light liquid 0.114 0.0199 

Heavy liquid 0.021 0.00862 

Compressor seals Gas 0.636 0.228 

Pressure relief valves Gas 0.16 0.104 

Connectors All 0.00025 0.00183 

Open-ended lines All 0.0023 0.0017 

Sampling connections All 0.0150 0.0150 

Note: kg/hr/source = kilograms per hour per source 

a

 Source: U.S. EPA, 1995b. 

b

 The refinery emission factors are for non-methane organic compound emission rates. c

 The SOCMI emission factors are for TOC (including methane). 

d

 The light liquid pump seal factor can be used to estimate the leak rate from agitator seals. 

If a process stream contains no ethane, the non-methane organic fraction is equal to the VOC fraction, 

which means the emission factor can be used without the correction ratio noted above, and the equation 

simplifies to Equation 2-6: 

 EVOC = FA × WFTOC × N (Eq. 2-6) 

Two guidelines when correcting the “FA” term when applied to refineries are as follows: 

 The correction should only be applied to equipment containing a mixture of organics and 

methane. 

 The maximum correction for the methane weight fraction should not be greater than 0.10, even if 

the equipment contains greater than 10 weight percent of methane. (This reflects the fact that the 

equipment for which the average refinery emission factors in Table 2-6 were developed typically 

contained 10 weight percent or less of methane). 

When using Methodology Ranks 4 and 5, speciated emissions are calculated using the same procedures 

described in Section 2.2.1 of this document. Preferably, facility- or process-specific compositional 

analyses would be available to develop constituent-specific emission estimates. When facility-specific 

data are not available, average stream compositions presented in Table 2-7 should be used. The average 

stream compositions presented in Table 2-7 were calculated based on the Petroleum Environmental 

Research Forum (PERF) refinery process stream speciation study (API, 2002). 

2.4.2 Calculating Hourly and Annual Equipment Leak Emissions 

Equations 2-5 and 2-6 provide the hourly emission rate. Because the components for which Methodology 

Ranks 4 or 5 for equipment leaks is applicable are not monitored, there are no additional considerations 

other than operating hours of the equipment (as seen in Equation 2-4) to convert the hourly emission 

estimate into an annual value. 
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2-18 

Table 2-7. Concentration of HAP in Refinery Process Unit Streamsa

Process Unit 

Average Weight Percent of Compound in Process Unit Stream 

1,3-Butadiene 

n-Hexane 

2,2,4-Trimethyl 

pentane 

Benzene 

Toluene 

Xylenes (total) 

Ethylbenzene 

Cumene 

1,2,4-trimethyl 

benzene 

Naphthalene 

Biphenyl 

Crude/Atmospheric 

distillation 

0.01 4.3 0.05 0.9 1.7 2.0 0.63 0.12 0.63 0.25 0.06 

Vacuum distillation - 0.01 0.003 0.003 0.04 0.04 0.02 - 0.02 0.12 0.09 

Coking 0.04 2.5 0.75 0.42 1.3 1.3 1.3 0.12 0.7 0.28 - 

Hydrocracking 0.025 1.9 1.0 1.3 2.7 2.7 0.7 0.09 1.3 0.20 - 

Catalytic cracking/FCCU 0.012 1.0 0.3 1.0 3.3 4.9 1.1 0.10 1.9 0.72 0.43 

Catalytic reforming/CRU 0.009 2.8 0.25 6.3 17.4 17.6 3.9 0.42 5.9 0.87 - 

Hydrotreating/ 

Hydrode sulfurization 

- 1.9 - 0.37 1.7 1.9 0.37 0.07 0.4 0.25 0.22 

Alkylation 0.22 1.6 25 0.03 2.0 0.08 - - - - - 

Isomerization - 3.2 0.01 0.5 0.6 0.15 - - - - - 

Polymerization - 0.5 0.7 1.2 - 1.8 1.2 0.09 - - - 

a

 Source: API, 2002. 

Example 2-5: Calculation of Equipment Leak Emissions Using Refinery Average 

Emission Factors 

At a refinery, assume there are 100 gas valves in a stream that, on average, contains 80 weight 

percent non-methane organic compounds, 10 weight percent water vapor, 10 weight percent 

methane, and no ethane (thus, the TOC weight percent would be 90). If the process operates 

8,000 hours per year, what are the hourly and annual VOC emissions from the 100 gas valves? 

Because the process stream contains no ethane, the average hourly VOC emissions from the 

gas valves in the stream can be calculated using the applicable emission factor from Table 2-5

and Equation 2-6. 

 EVOC = FA × WFTOC × N 

 = 0.0268 kg NMOC/hr/gas valve × 0.9 × 100 gas valves 

 = 2.412 kg VOC/hr 

The annual emissions from the valves in the stream are calculated using Equation 2-4 (with ETOC

replaced by EVOC). 

 EVOC, annual = EVOC × H 

 = 2.412 kg VOC/hr × 8,000 hr/yr 
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3. Storage Tanks 

Storage tanks (which are also sometimes referred to as storage vessels) are used in refineries for storing 

and dispensing various liquids used in the refining process. These various liquids are typically organic 

liquids, also known as petroleum liquids, which are a mixture of hydrocarbons, such as gasoline and 

crude oil. Depending on the specific design and construction of the tank and the characteristics of the 

petroleum liquids, storage tanks may emit significant levels of VOC and HAP during typical operation, 

venting, and tank filling or dispensing. 

The basic designs for storage tanks include horizontal and vertical fixed-roof tanks, external floating roof 

tanks, internal floating roof tanks, and domed external floating roof tanks. Chapter 7.1 (Organic Liquid 

Storage Tanks) of EPA’s Compilation of Air Pollutant Emission Factors (AP-42) provides detailed 

descriptions of the characteristics specific to each tank type (U.S. EPA, 1995a [some sections were 

updated in 2006]). 

The emission estimation methods for storage tanks are presented in Table 3-1. These methods are ranked 

according to anticipated accuracy. There are three primary estimation methods: (1) direct measurement, 

(2) tank-specific modeling, and (3) default tank emission factors. Direct measurements can only be taken 

from storage tanks that are covered and vented to a control device. Tank-specific modeling can be 

accomplished with emission equations, such as those presented in AP-42 or by computer-based models 

designed to implement these equations (e.g., TANKS v4.09D; U.S. EPA, 2006). Most refinery owners 

and operators will have sufficient data to use the tank-specific modeling approach and this method should 

be used for most refinery storage vessels. In rare cases when tank-specific data are not available, 

engineering estimates can be made using actual or estimated production quantities and default emission 

factors. For the purposes of the refinery ICR, all storage tank emission estimates should be developed 

using Methodology Ranks 1 or 2. 

Table 3-1. Summary of Typical Hierarchy of Storage Tank Emission Estimates 

Rank 

Methodology 

Description Application Data Requirements 

1 Direct measurement Covered and vented 

storage tanks 

Constituent concentration and flow rate 

2 Tank-specific modeling All petroleum liquid storage 

tanks 

Tank type, tank dimensions, stored liquid 

properties and constituent concentrations, 

tank condition/fitting information, throughput 

3 Default tank modeling Not applicable for refinery 

ICR emission estimates 

3.1 Methodology Rank 1 for Storage Tanks 

Emissions from fixed-roof storage tanks may be purged (e.g., tanks under a nitrogen blanket) and vented 

to a control device; these emissions can be directly measured at the outlet of the control device using the 

direct measurement methods for process vents or combustion sources as described in Sections 4,

Stationary Combustion Sources, and 5, Process Vents, of this Refinery Emissions Protocol document. It is 

likely that the control device will serve a group of tanks; it is acceptable to report the cumulative 

emissions from the group of storage tanks if this is the case. 

For some control devices, such as flares, thermal oxidizers, or carbon adsorption systems, it may be 

possible to measure the concentration of the gas upstream of the control device and estimate the emissions 

using an assumed control device efficiency (for more details on these types of methods, see the discussion 

at the end of Section 3.2 below; Section 4, Stationary Combustion Sources; and/or Section 6, Flares). 
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This method is also recommended as a means to estimate storage tank emissions when the emissions from 

the storage tank(s) are routed to a control device that also serves other refinery emission sources. In this 

case, the concentration and flow rate of the storage tank off-gas can be measured prior to combining the 

stream with other non–storage tank emissions. The resulting constituent mass flow rates can be corrected 

for the control device efficiency using the methods described in Chapter 6 (Flares) to estimate the 

emissions associated with the storage tank(s) that are released to the atmosphere. 

There are other direct measurement methods that have been used to measure emissions from storage tanks 

even when the emissions from the tank are not vented (i.e., DIAL [Differential Absorption LIDAR] 

techniques); however, these methods do not provide continuous monitoring and have additional 

limitations (requiring consistent wind direction, etc.). Therefore, at the present time they are not 

recommended as primary techniques for annual emission estimation. 

If direct measurement methods are used, emissions from the tank during degassing, cleaning, or drained 

idle periods may or may not be included, depending on how these gases are vented. If these gases are 

routed to the same control device as used during normal operations, the measured emissions will account 

for these periods. If these emissions are not monitored using direct measurement methods, the emissions 

from the tank during degassing and cleaning should be estimated separately using the methods provided 

in Section 11, Startup and Shutdown, of this Emissions Protocol Document.

3.2 Methodology Rank 2 for Storage Tanks 

Except for the limited number of storage tanks whose emissions are collected and controlled external to 

the storage tank, EPA recommends that the emission estimation procedures detailed in Chapter 7.1 of AP42 (U.S. EPA, 1995a) be used to calculate air pollutant emissions from organic liquid storage tanks. There 

are many tools available, such as TANKS v4.09D emission estimation software that can be used to 

perform the necessary calculations. TANKS v4.09D software can be downloaded for free at: 

http://www.epa.gov/ttn/chief/software/tanks/index.html under the How to Get TANKS 4.09D link. 

Because TANKS v4.09D is widely used, Appendix C of this Refinery Emissions Protocol document 

provides tips and insights on using the TANKS program. 

Key things to consider when estimating emissions from storage tanks (whether using the AP-42 equations 

directly or when using TANKS v4.09D or other software packages) include: 

1. Each tank should be modeled individually using site-specific conditions. There may be instances in 

which a set of tanks have identical properties and materials and very similar throughputs so that the 

emissions from a single storage tank can be modeled and used as the emissions for each tank in the 

set. However, this approach should be limited to situations where the tanks, contents, and 

throughputs are effectively identical. In all other cases, it is recommended that individual tank data 

be entered into the TANKS program (or other similar software), and the emission results for 

individual tanks be reported. 

2. Each tank should be modeled based on the vapor pressure and composition of the material stored in 

the tank. The TANKS model has default vapor pressure and composition for certain streams; 

however, these defaults should not be used unless the default parameters have been specifically 

evaluated and determined to adequately represent the stored liquid. For example, it is possible that a 

specific gasoline default stream (where different defaults are available for different Reid vapor 

pressures) will match well the gasoline stored in certain tanks, but it is less likely that the single 

crude oil default in TANKS will match the crude oil stored in the crude oil tanks. 

3. For the internal floating roof tank, the external floating roof tank, and the domed external floating 

roof tank, the tank fittings should be selected to represent the specific characteristics of each 

individual storage tank. You should not use the “default” fitting settings when using TANKS 

v4.09D, particularly for the type and control for guide poles. The default fitting settings should be 
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reviewed and revised to properly account for the number and control status of the specific tank’s 

fittings. 

4. The storage tanks should be modeled using monthly parameters, including average monthly 

measured tank liquid temperatures, when available. In TANKS, selecting the city will set the 

meteorological data that will be used in the calculations. Even if you select the monthly calculation 

option, the liquid temperature remains at the annual average. As such, the TANKS program will not 

adequately account for the monthly variations in emissions. Also, for intermediate process tanks 

with floating roofs that store liquids that are generally warmer than ambient temperature, TANKS 

will underestimate the emissions.1

 Therefore, for storage tanks with throughputs that vary 

significantly with the seasons and floating roof tanks that store warm process fluids, the equations in 

Chapter 7.1 of AP-42 should be used directly to more accurately estimate the annual emissions. 

5. Special calculations should be performed to account for tank roof landings, tank degassing, and tank 

cleaning, and these estimates should be included in the final annual emissions reported for each tank. 

The TANKS model does not currently contain algorithms for estimating emissions from tank roof 

landings. These emissions should be estimated separately for each landing event using the methods 

provided in Section 7.1.3.2.2 of the 2006 update of Section 7.1 of AP-42. Tank degassing emissions 

can be calculated using the liquid heal method described in Section 11, Startup and Shutdown, of 

this Refinery Emissions Protocol document. 

6. Emission estimates should be calculated and reported for individual pollutants. The TANKS 

program typically provides total hydrocarbon emission estimates, but can also provide estimates for 

individual pollutants. 

7. Maximum hourly average emission rates for each tank should be calculated based on the reasonable 

worst-case (high emission rate) situation for a given storage tank, which will generally correspond to 

the emissions while the tank is actively filling. Factors that should be considered are the volatility of 

the material stored, the filling rate, the bulk liquid and ambient air temperature, and the wind speed. 

Higher emissions will occur when these parameters are at their highest values. Note that the TANKS 

program is primarily designed to estimate long-term, annual average emissions and cannot be easily 

manipulated to estimate the maximum hourly emission rate. Also note that the maximum hourly 

average emission rate should not be based on the tank’s degassing emission estimate. 

For fixed-roof tanks that are vented to a control device, but for which flow and composition data are not 

measured (i.e., data are not available to use Methodology Rank 1for storage tanks), the pre-control 

emissions from the fixed-roof storage tanks can be estimated using the appropriate equations for fixedroof storage tanks presented in Chapter 7.1 of AP-42 (U.S. EPA, 1995a). The post-control device 

emissions are then estimated from the pre-control emission estimates and the efficiency of the control 

device using Equation 3-1. 

⎟

⎠

⎞ ⎜

⎝

⎛ = ×

100%

CD 1- eff

i unc,i E E (Eq. 3-1) 

where: 

 Ei = Emission rate of pollutant “i” (tons/yr) 

 Eunc,i = Projected emission rate of pollutant “i” assuming storage tank or unit does not have an 

add-on control device (tons/yr) 

 CDeff,i = Control device efficiency Feff for pollutant “i” (weight percent). See Table 3-2 for 

default control efficiencies for various control devices. 

 

1 The TANKS program includes an algorithm for calculating emissions from heated tanks, but it is only applicable to 

tanks with horizontal or vertical fixed roofs. 
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Table 3-2. Default Control Efficiencies for Different VOC Control Devices 

Control Device Pollutants 

Control Device 

Efficiency 

Refrigerated Condenser All VOC constituents Variable based on 

constituents and 

operating 

temperaturea

Thermal oxidizer All VOC constituents 98% 

Catalytic oxidizer All VOC constituents 98% 

Carbon adsorption VOC constituents other than those listed in table note b 95% 

Constituents listed in table note b 0% 

a

 The control efficiency of a condenser should be determined based on the operating conditions of the condenser 

and composition of the vent stream following the methods Methods for Estimating Air Emissions from Chemical 

Manufacturing Facilities (EIIP, 2007, Section 4.2.3) 

b

 The following compounds have extremely low adsorptive capacities on activated carbon: acetaldehyde, 

acetonitrile, acetylene, bromomethane, chloroethane, chloromethane, ethylene, formaldehyde, methanol, and vinyl 

chloride. 

3.3 Methodology Rank 3 for Storage Tanks 

Refinery owners and operators are expected to have tank-specific information and should use 

Methodology Rank 2 for storage tanks. Methodology Rank 3 for storage tanks (default emission factors) 

was originally intended for state and local agency staff that may not have access to the tank-specific 

information needed to implement the AP-42 modeling equations. Because this version of the Refinery 

Emissions Protocol document is intended specifically for refinery owners and operators in completing the 

emission inventory estimates required by the ICR, the Methodology Rank 3 for storage tanks has been 

deleted from this version of the protocol. Based on the information collected as a result of the ICR, we 

will determine if a Methodology Rank 3 for storage tanks is appropriate and, if appropriate, we will 

provide the methodology and default emission factors at that time. 
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4. Stationary Combustion Sources 

Petroleum refineries include numerous stationary combustion sources, the most common of which are 

process heaters, boilers, internal combustion engines, and combustion turbines. These combustion sources 

are vent (point) sources that occur throughout the process area of the refinery. The size of the vent stack 

varies with the size of the source (typically measured in terms of the rate that fuel is burned). Process 

heaters are used to indirectly preheat feedstock or process fluids for a given process, to reheat 

intermediates of a process, or to heat distillation columns (the latter are often termed “reboilers”). These 

emission sources are typically localized at or near the process requiring the heater (or reboiler). Boilers 

are used to generate steam for various refinery operations and to raise the temperature of feedstocks and 

process streams. The primary fuel for nearly all petroleum refinery process heaters and boilers is refinery 

fuel gas, which is a mixture of uncondensed overhead gases from distillation columns (also referred to as 

“still gas”) and natural gas. Still gas is produced from a variety of refinery process units, including 

atmospheric crude oil distillation units, fluid catalytic cracking units, catalytic reforming units, fluid and 

delayed coking units, and hydrocracking units. Other fuels, such as natural gas only, fuel oil, and residual 

oil, are also used. Internal combustion engines have a variety of uses, including powering fire suppression 

systems, and supplying emergency back-up power. Internal combustion engines generally combust 

natural gas, gasoline, or diesel fuel oil. Combustion turbines are used for cogeneration, and typically 

combust natural gas or refinery fuel gas. 

In addition to refinery fuel gas, some petroleum refineries also produce petroleum coke. The petroleum 

coke produced by a coking unit is generally referred to as green petroleum coke or fuel grade coke. Some 

refineries may use green petroleum coke as fuel in boilers to produce steam or electricity. Green 

petroleum coke is expected to contain relatively high concentrations of sulfur and metals when compared 

with other fuels used at a refinery. Green petroleum coke may be purified in a calcining unit for use in 

industrial applications, most often as anode material in the manufacture of aluminum. Consequently, 

calcined petroleum coke is often referred to as anode grade coke. Emissions from coke calcining are 

described in more detail in Section 5.6.3, Coke Calcining, of this Refinery Emissions Protocol document. 

Alternatively, green petroleum coke may be gasified with steam and either air or oxygen (O2) to form a 

low (using air) to medium (using O2) heating value synthesis gas (or syngas) for subsequent use as a fuel 

gas. There are no direct emissions from the coke gasification process; emissions from the combustion of 

syngas can be estimated using the methods provided in this section. 

Table 4-1 summarizes the hierarchy of emission estimation methods for stationary combustion sources. 

Each refinery may use a combination of different methods, such as Methodology Rank 1 for criteria 

pollutants such as sulfur dioxide (SO2) and NOx, and Methodology Rank 2 or 3 to estimate emissions of 

organic or metal compounds. Different methodologies may be used for each combustion source for each 

pollutant based on the type of monitoring data available for each source (e.g., Methodology Rank 1 may 

be used for estimating NOx emissions for one combustion source for which continuous emission 

monitoring systems (CEMS) data are available, while Methodology Rank 4 may be used to estimate NOx

emissions for another combustion source at the same facility where no CEMS data or emission test data 

are available). It is also important to note that the selection of Methodology Rank 3A or Methodology 

Rank 3B will depend on factors such as whether the pollutant being estimated has a reduced form (e.g., 

reduced sulfur compounds form SO2 when oxidized) that can be continuously monitored, the variability 

of the combustion source, and the date of the most recent stack test. The remainder of this section 

provides additional detail and guidance regarding the implementation of these methods. 

A complete inventory for combustion sources will include emission estimates for PM, SO2, NOx, VOCs,1

and carbon monoxide (CO). Depending on the fuel combusted, a complete inventory will also include 

 

1

 Total hydrocarbon [THC] may be estimated as a surrogate for VOC. 
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emission estimates for hydrogen sulfide; metals, including but not limited to arsenic, chromium, mercury, 

lead, and selenium; organic compounds, including but not limited to benzene, formaldehyde, 1,3-

butadiene, and naphthalene and other polycyclic organic matter; and dioxins and furans. It is important to 

note that this list is not exhaustive; if there is evidence that a combustion source at a refinery emits a 

pollutant (e.g., site-specific emission test data for an additional compound or a relevant emission factor 

for an additional compound), an emission estimate should be included in a complete inventory, even if 

that pollutant is not specifically identified in this document. 

Table 4-1. Summary of Typical Hierarchy of Stationary Combustion Source Emission Estimates 

Rank Measurement Method Additional Data Needed 

1 Direct measurement (continuous emission 

monitoring systems [CEMS]) for both flow rate and 

gas composition 

 Pressure, temperature, and moisture content 

(depending on the monitoring system) 

2 Direct measurement (CEMS) for gas composition 

Use of F factors 

 Fuel usage 

 Heat content of fuel (depending on units of 

source-specific emission factors) 

3A Fuel analysis/mass balance  Fuel usage 

 Assumed destruction efficiency 

3B Source-specific stack testing to calculate sourcespecific emission correlations or factors  Fuel usage 

 Heat content of fuel (depending on units of 

source-specific emission factors) 

4 Default emission factors  Fuel usage 

There are many sources that describe emission methodologies for combustion sources, particularly boilers 

and internal combustion sources, including Chapter 2 in the Emission Inventory Improvement Program 

Technical Report Series (ERG, 2001), 2008 Emissions Inventory Guidelines (TCEQ, 2009), and A 

Customized Approach for Quantifying Emissions for the Electric Power Generation Sector in Mexico

(The United States–Mexico Foundation for Science, 2008). These documents include many examples and 

sample calculations for liquid and solid fuels and should be consulted for more information if needed. In 

addition, the American Petroleum Institute (API) has posted a Compendium of Greenhouse Gas 

Emissions Methodologies for the Oil and Natural Gas Industry on their Web site. While this document is 

focused on estimating GHG emissions, it contains information on how to estimate combustion gas flows 

and how to estimate emissions from various types of combustion sources, and it includes useful 

conversion factor discussions and examples. 

4.1 Methodology Rank 1 for Stationary Combustion Sources 

Many stationary combustion sources will have a CEMS for NOx and/or SO2. A CEMS is a comprehensive 

unit that continually determines gaseous or PM concentrations or emission rates using pollutant analyzer 

measurements and a conversion equation, graph, or computer program to produce results in the desired 

units. A CEMS that includes a flow rate monitor, which is needed to determine mass emission rates, such 

as those needed for an emission inventory, is also referred to as a continuous emission rate monitoring 

system (CERMS). The CEMS or CERMS continually determines the flow rate of the exhaust gas, 

analyzes the composition or specific pollutant concentration in the exhaust gas, and records the results. 

There are two main types of CEMS: in-situ and extractive. An in-situ CEMS measures and analyzes the 

emissions directly in a stack. There is less sample loss associated with the in-situ CEMS compared to the 

extractive CEMS because the sample lines of an extractive system can leak, freeze, or clog, or pollutants 

can be lost because of adsorption, scrubbing effects, or condensation. In an extractive CEMS, the sample 

gas is extracted from the gas stream and transported to a gas analyzer for the measurement of the 

contaminant concentration. Because an extractive CEMS is located outside the stack, the sampling 
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instruments are not affected by stack conditions, maintenance and replacement are generally simpler, and 

the cost is lower than with an in-situ CEMS, although extra costs are incurred for the sampling and 

conditioning system for an extractive CEMS (Levelton Consultants, 2005). 

The pollutant concentration recorded by a CEMS is generally on a concentration basis, such as parts per 

million. The CEMS may also include a diluent monitor (e.g., O2) for correcting the concentrations to a 

fixed excess air concentration. For in-situ CEMS, these measurements are made at stack conditions so 

that the concentrations would be determined on a “wet basis.” That is, the concentrations are based on the 

total amount of gas, including water vapor. For extractive CEMS, the gas is often conditioned to remove 

water vapor before analysis, so the concentrations are commonly determined on a “dry basis.” Gas flow 

measurements are made at stack conditions, so the flow rate will be in terms of actual gas volume on a 

wet basis. If the gas composition is determined on a dry basis, then a moisture content measurement is 

needed to convert the flow rate to a dry basis (or convert the composition to a wet basis) so that both 

measurements are on the same basis, and many gas flow monitors contain temperature and pressure 

monitors to allow conversion of the flow to standard conditions for this purpose. It is important to note 

that care must be taken to ensure that the gas and flow measurements are made on the same basis and in 

the same terms as the permitted limits, if applicable, or that appropriate ancillary measurements are made 

to perform the necessary unit conversions. 

The following general equation (Equation 4-1) is used for determining a mass emission rate from CEMS: 

() ( ) [ ] ( )

100%

1

1

∑ 20

= ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

× × ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

×⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛ = × − × × ×

N

n

N

o

n

n

i n i o

i n H n M K

P

P

T

T

MVC

C MW

E Q f (Eq. 4-1) 

where: 

 Ei = Emission rate of pollutant “i” (tons per year [tons/yr]). 

 N = Number of measurement periods per year (e.g., for hourly measurements, N = 8,760). 

 n = Index for measurement period. 

 (Q)n = Volumetric flow rate for measurement period “n” (actual cubic feet per minute [acfm]). 

If the flow rate meter automatically corrects for temperature and pressure, then replace 

“To ÷ Tn × Pn ÷ Po” with “1.” If the pollutant concentration is determined on a dry basis 

and the flow rate meter automatically corrects for moisture content, replace the term 

[1-(fH20)n] with 1. 

 (fH2O)n = Moisture content of exhaust gas during measurement period “n,” volumetric basis 

(cubic feet water per cubic feet exhaust gas). 

 (Ci)n = Concentration of pollutant “i” in the exhaust gas for measurement period “n” (volume 

%, dry basis). If the pollutant concentration is determined on a wet basis, then replace 

the term [1−(fH20)n] with 1. 

 MWi = Molecular weight of pollutant “i” (kilogram per kilogram mole [kg/kg-mol]). 

 MVC = Molar volume conversion factor = 849.5 standard cubic feet per kilogram mole 

(scf/kg-mol) at 68°F (528°R) and 1 atmosphere (atm). 

 To = Temperature at “standard conditions” (528 °R). 

 Tn = Temperature at which flow is measured during measurement period “n” (°R). 

 Pn = Average pressure at which flow is measured during measurement period “n” (atm). 

 Po = Average pressure at “standard conditions” (1 atm). 

 MN = Minutes per measurement period (minutes per measurement period “n”). This term can 

be calculated by dividing 525,600 minutes per year (min/yr) by the number of 

measurement periods per year (“N”). 

 K = Conversion factor = 2.2046/2,000 (tons per kilogram [tons/kg] = 0.0011023 tons/kg. 
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A CEMS records multiple measurements per hour; the frequency depends on the pollutant being 

measured and the type of CEMS. For example, a CEMS monitoring benzene concentration using gas 

chromatography may only sample and record a measurement every 15 minutes, while a CEMS 

monitoring SO2 concentration may record a measurement every minute. These individual measurements 

can be used to calculate annual emissions in two ways. The most common method is for the CEMS to 

average the measurements within each hour and develop 8,760 hourly average concentrations and flow 

rates that can be summed. Example 4-1 demonstrates the calculation of NOx emissions for 1 hour for a 

combustion unit firing refinery fuel gas based on an hourly average concentration and flow rate. This 

method is best suited for measurements that are fairly consistent and stable over the course of an hour. 

The other method is to determine the emission rate for each recorded measurement based on the 

concentration and flow rate for that measurement. In other words, if the CEMS records measurements 

every minute, then the emission rate is determined per minute and hourly emissions are determined by 

summing the 60 applicable emission rates; if the CEMS records measurements every 5 minutes, then the 

emission rate is determined for each 5-minute interval and hourly emissions are determined by summing 

the 12 applicable emission rates. This method may be more accurate than hourly averages if the 

combustion source’s flow rate varies significantly within an hour. 

Example 4-1: Calculation of NOx Emissions Using a CEMS 

The following example shows the calculation for 1 hour (60 minutes); the total emissions 

during any period (i.e., day, month, quarter, or year) may be calculated as the sum of the 

hourly emissions determined by the CEMS. In terms of Equation 4-1, “i” is NOx and the index 

for the period in this example is 1, so the result “E” is in tons per hour. 

Calculate hourly NOX emissions for a 150 million British thermal units per hour (MMBtu/hr) 

unit burning refinery fuel gas given that the following data have been collected: 

– The hourly average NOx concentration calculated by the CEMS for this hour is 60 parts 

per million by volume (ppmv), wet basis 

– The hourly average flow rate calculated by the CEMS for this hour is 500,000 acfm, wet 

basis 

– The unit operated at standard conditions for the full hour. 

Equation 4-1 should be used to calculate the hourly emissions: 

() ( ) [ ] ( ) M K

P

P

T

T

MVC

C MW

E Q f

N

n

N

o

n

n

NOx n NOx o

NOx ∑ n H n

= ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛ = × − × × × × × ×

1

20 100%

1

= 500,000 × 1 × (60 ÷ 1,000,000) × 46.01 ÷ 849.5 × 1 × 1 × 60 × 0.0011023 

= 0.1075 tons per hour (tons/hr). 

Rounded to two significant figures, the hourly emissions are 0.11 tons/hr. 

If the combustion source did not operate the entire hour, multiply the hourly emissions by the 

fraction of the hour that the unit operated (e.g., if the unit operated for 30 minutes, then 

emissions for this hour would be 0.1075 tons/hr × 0.5 = 0.054 tons/hr). 

If the combustion source operated steadily and continuously for an entire year and the 

emission rate remained perfectly constant over that year, annual emissions would be 

0.1075 tons/hr × 8,760 hours per year (hr/yr) = 940 tons/yr. 
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4.2 Methodology Rank 2 for Stationary Combustion Sources 

Because the emission standards for stationary combustion sources are often provided on a concentration 

basis or on a mass per heating–value basis, many stationary combustion sources will have a CEMS for 

pollutant concentrations, but may not directly measure exhaust gas flow. In these cases, fairly accurate 

exhaust gas flow rates can be calculated from the refinery fuel gas composition and fuel flow 

measurements. This method is commonly referred to as the “F factor” method, and procedures for 

conducting a fuel analysis and calculating estimated emissions are described in EPA Method 19 (40 CFR 

Part 60, Appendix A-7). 

EPA Method 19 includes many equations that can be used to calculate emissions depending on moisture 

measurements and whether pollutant concentrations and O2 or CO2 content are measured on a wet or dry 

basis, and each equation uses one of three different types of F factors. The calculation of the different F 

factors is described in Section 12.3.2 of Method 19. In lieu of this calculation, Table 19-2 of EPA Method 

19 includes default F factors for some common types of fuel that could be used; however, F factors for 

refinery fuel gas are not included in Table 19-2. 

Refinery fuel gas generally includes many different components; therefore, one equation that can be used 

to calculate the F factor in this situation is an adapted version of Equation 19-16 in EPA Method 19 for 

multiple fuels. In Equation 4-2, the dry F factor, Fd, is calculated assuming both the pollutant 

concentration and the O2 content are measured on a dry basis: 

( )

( )⎟

⎟

⎟

⎟

⎠

⎞

⎜

⎜

⎜

⎜

⎝

⎛

×

×

= ×

∑

∑

=

=

n

i

i i

n

i

i i

d

X MHC

X MEV

F K

1

1

 (Eq. 4-2) 

where: 

 Fd = Volume of combustion components resulting from stoichiometric combustion per unit 

of heat content (dry standard cubic feet per million British thermal unit [dscf/MMBtu]) 

 K = Conversion factor, 106

 (Btu/MMBtu) 

 n = Number of fuels or fuel components 

 i = Index for fuels or fuel components 

 Xi = Mole or volume fraction of each component in the refinery fuel gas 

 MEVi = Molar exhaust volume (dry standard cubic feet per mole [dscf/mol]) 

 MHCi = Molar heat content (British thermal units per mole [Btu/mol]) 

Table 4-2 includes values for the molar exhaust volume and molar heat content for common constituents 

of refinery fuel gas. It is important to note that these calculations are based on the higher heating value of 

the fuel gas (referred to as gross calorific value in EPA Method 19). 

Table 4-2. Molar Exhaust Volumes and Molar Heat Content of Refinery Fuel Gas Constituents 

Constituent MEVa (dscf/mol) MHCb (Btu/mol) 

Methane (CH4) 7.28 842 

Ethane (C2H6) 12.94 1,475 

Hydrogen (H2) 1.61 269 

Ethene (C2H4) 11.34 1,335 

(continued) 
Version 2.1.1 

Final ICR Version – Corrected Section 4—Stationary Combustion Sources 

4-6 

Table 4-2. Molar Exhaust Volumes and Molar Heat Content of Refinery Fuel Gas Constituents 

(continued) 

Constituent MEVa (dscf/g-mol) MHCb (Btu/g-mol) 

Propane (C3H8) 18.61 2,100 

Propene (C3H6) 17.01 1,947 

Butane (C4H10) 24.28 2,717 

Butene (C4H8) 22.67 2,558 

Inerts 0.85 0 

a

 MEV = molar exhaust volume (dry standard cubic feet per gram-mole [dscf/g-mol]) b

 MHC = molar heat content (Btu per gram-mole [Btu/g-mol]); higher heating value basis 

The F factor can be used to calculate emissions in one of two ways. In the first option, the F factor, the 

amount of fuel combusted, and the heat content of the fuel can be used to calculate the volumetric flow 

rate of the exhaust gas, (Q)n, using the following equation. 

(20.9 % )

20.9

2d

n d f O Q F Q HHV − = × × × (Eq. 4-3) 

where: 

 Qn = Volumetric flow rate for measurement period “n” (dry standard cubic feet per minute 

[dscfm]) 

 Fd = Volume of combustion components per unit of heat content (dscf/MMBtu) 

 Qf = Volumetric flow rate of fuel (dscfm) 

 HHV = Higher heating value of fuel (million British thermal units per standard cubic foot 

[MMBtu/scf]) 

 %O2d = Concentration of O2 on a dry basis (percent) 

Once the volumetric flow rate is known, emissions can be calculated using Equation 4-1 as in 

Methodology Rank 1 for stationary combustion sources. It is important to note that when using the F 

factor method as indicated here, the exhaust gas flow rate will be in units of dry standard cubic feet per 

minute, so the temperature and pressure correction terms are not needed. A moisture correction term is 

not needed when the concentration measurement is also made on a dry basis. If the concentration 

measurements are made on a wet basis, then they must be corrected to a dry basis by dividing by the 

[1−(fH20)n] term. 

In the second option, the F factor can be used to calculate an emission factor (Equation 4-4) that can then 

be multiplied by the higher heating value of the fuel to estimate emissions (Equation 4-5). 

(20.9 % )

20.9

2d

i d d O

EF C F − = (Eq. 4-4) 

where: 

 EFi = Emission rate of pollutant (pounds per million British thermal unit [lb/MMBtu]) 

 Cd = Pollutant concentration, dry basis (pounds per standard cubic foot [lb/dscf]) 

 Fd = Volume of combustion components per unit of heat content (dscf/MMBtu) 

 %O2d = Concentration of O2 on a dry basis (percent) 
Version 2.1.1 

Final ICR Version – Corrected Section 4—Stationary Combustion Sources 

4-7 

Ei = EFi × (60 × Qf )× HHV (Eq. 4-5) 

where: 

 Ei = Emissions of pollutant “i” (pounds per hour [lb/hr]) 

 EFi = Emission rate of pollutant (lb/MMBtu) 

 Qf = Volumetric flow rate of fuel (dscfm) 

 60 = Conversion factor, minutes per hour 

 HHV = Higher heating value of fuel (MMBtu/scf) 

Example 4-2 demonstrates the calculation of an F factor based on a fuel analysis for refinery fuel gas. 

Examples 4-3 and 4-4 demonstrate the first and second options, respectively, to estimate emissions using 

the F factor. As previously mentioned, if the result of a calculation is an hourly emission estimate, then 

the calculation process should be repeated for each hour in the year, or 8,760 times. For example, the 

hourly pollutant and O2 concentrations from the CEMS should be used in Equation 4-4 to calculate an 

emission factor for each hour in the year. That emission factor and the hourly measurements of the fuel 

flow rate should then be used in Equation 4-5 to determine the hourly emissions for each hour in the year. 

The sum of all of those hourly emission estimates is the annual emission estimate. 

Example 4-2: Calculation of Fuel-Specific F Factor 

The CEMS measures SO2 and O2 content on a dry basis, so in lieu of using a default F factor, 

the facility can use fuel analysis results and Equation 4-2 to calculate an Fd factor 

(scf/MMBtu). The Fd factor is calculated at standard conditions of 20°C (68°F) and 29.92 

inches of mercury. 

The fuel analysis revealed the following mole fractions: 

Methane 0.44 Propene 0.03 

Ethane 0.04 Butane 0.17 

Hydrogen 0.06 Butene 0.01 

Ethene 0.01 Inerts 0.04 

Propane 0.2 

Equation 4-2 is used to calculate Fd as follows: 

( ) ( ) ( ) ( ) ( )

( )( )( ) ( )

( ) ( ) ( )( ) ( )

( )( )( ) ( )]

[

]

[

3 6 3 6 4 10 4 10 4 8 4 8

4 4 2 6 2 6 2 2 2 4 2 4 3 8 3 8

3 6 3 6 4 10 4 10 4 8 4 8

4 4 2 6 2 6 2 2 2 4 2 4 3 8 3 8

C H C H C H C H C H C H inerts inerts

CH CH C H C H H H C H C H C H C H

C H C H C H C H C H C H inerts inerts

d CH CH C H C H H H C H C H C H C H

X MHC X MHC X MHC X MHC

X MHC X MHC X MHC X MHC X MHC

X MEV X MEV X MEV X MEV

F K X MEV X MEV X MEV X MEV X MEV

× + × + × + ×

× + × + × + × + × +

× + × + × + × ÷

= × × + × + × + × + × +

Fd = 106 × [(0.44 × 7.28) + (0.04 × 12.94) + (0.06 × 1.61) + (0.01 × 11.34) + (0.2 × 18.61) + (0.03 

× 17.01) + (0.17 × 24.28) + (0.01 × 22.67) + (0.04 × 0.85)] ÷ [(0.44 × 842) + (0.04 × 1475) + 

(0.06 × 269) + (0.01 × 1335) + (0.2 × 2100) + (0.03 × 1947) + (0.17 × 2717) + (0.01 × 2558) 

+ (0.04 × 0)] 

= 106

 × 12.55 ÷ 1425 

= 8,809 dscf/MMBtu 
Version 2.1.1 

Final ICR Version – Corrected Section 4—Stationary Combustion Sources 

4-8 

Example 4-3: Calculation of Exhaust Flow Rate from F Factor 

From Example 4-2, the F factor is 8,809 dscf/MMBtu. The measured SO2 concentration is 20 

ppmv (dry basis), the measured O2 concentration is 6% (dry basis), the higher heating value is 

1,300 Btu/scf, and the fuel flow rate is 500 dscfm. Equation 4-3 should be used to calculate 

the exhaust flow rate from F factor as follows: 

(20.9 % )

20.9

2d

n d f O Q F Q HHV − = × × ×

 Qn = (8,809) × (500) × (1,300 ÷ 106

 [Btu/MMBtu]) × (20.9 ÷ (20.9 – 6)) 

 Qn = 8,031 dscfm 

Use this value of Qn in Equation 4-1 without the temperature, pressure, and moisture 

correction terms to estimate hourly emissions as follows: 

() ( ) [ ] ( ) M K

MVC

MW

%

C

E Q f N

i n i

SO n H n = × − × × × ×

100

1 2 20

ESO2

 = 8,031 × 1 × (20 ÷ 1,000,000) × 64.06 ÷ 849.5 × 60 × 2.2046 = 1.6 lb/hr 

Example 4-4: Calculation of Emissions Factor from F Factor 

Given the same measurements as Example 4-3, calculate hourly SO2 emissions. 

First, the following equation should be used to convert the concentration to the correct units 

(from Table 19-1 of EPA Method 19, multiply the SO2 concentration in ppm by 1.660 × 10-7

to convert to lb/scf [see also Equation 4-7 of this section]): 

 Cd = 20 ppm × (1.660 × 10-7) lb/scf/ppm 

 Cd = 3.322 × 10-6 lb/scf 

Second, Equation 4-4 should be used to calculate the emission factor: 

(20.9 % )

20.9

2

2

d

SO d d O

EF C F − =

 EFSO2

 = (3.322 × 10-6) × (8,809) × (20.9 ÷ (20.9 – 6)) 

 EFSO2

 = 0.041 lb/MMBtu 

Finally, Equation 4-5 should be used to calculate the hourly emissions (the fuel flow rate is 

500 dscfm, or 30,000 dscf/hr [500 dscfm × 60 minutes per hour (min/hr)]) 

ESO = EFSO ×Qf × HHV 2 2

 ESO2

 = (0.041) × (30,000) × (1,300 ÷ 106 [Btu/MMBtu]) 

 ESO2

 = 1.6 lb/hr 

If the combustion source operated steadily and continuously for an entire year and the 

emission rate remained perfectly constant over that year, then the annual emissions would be 

1.6 lb/hr × 8,760 hr/yr ÷ 2,000 lb/ton = 7.0 tons/yr. 
Version 2.1.1 

Final ICR Version – Corrected Section 4—Stationary Combustion Sources 

4-9 

4.3 Methodology Rank 3A for Stationary Combustion Sources 

Fuel analysis can be used to predict emissions of pollutants such as SO2 by examining the compounds in 

the fuel being combusted. Given a known concentration of a compound, either a pollutant or pollutant 

precursor (e.g., hydrogen sulfide [H2S] or other reduced sulfur compounds for purposes of estimating SO2

emissions), emissions of the pollutant can be calculated by assuming that all of that compound is emitted 

(e.g., all of the reduced sulfur is oxidized to SO2). Alternatively, if some of the compound is not 

combusted (i.e., is in a different physical or chemical state such as ash or unburned hydrocarbons), then 

based on the laws of mass conservation, less than 100% of the pollutant is emitted as air emissions (ERG, 

2001). In this case, it may be possible to determine the emissions actually resulting from combustion by 

considering the uncombusted compounds in a mass balance analysis. 

As mentioned in the introduction to Section 4, Methodology Rank 3A for stationary combustion sources 

is considered a more accurate method of emission estimation than Methodology Rank 3B for stationary 

combustion sources for certain pollutants, namely SO2, particularly if the concentration of the compound 

of interest in the fuel and the fuel flow rate are continuously measured. This may also be the case if the 

available source tests are not recent or if the combustion unit’s operation varies significantly enough that 

there are concerns about the accuracy of applying an emission factor developed at one set of operating 

conditions. For example, a test of NOx emissions from a process heater performed at high capacity may 

not apply when the process heater is firing at a lower rate. As the heater firing rate decreases, the operator 

increases the oxygen content to ensure stable operation, and this increase in oxygen content may lead to 

higher concentrations of NOx. 

Equation 4-6 is a general equation used to determine a mass emission estimate from fuel analysis data for 

gaseous fuels (for fuel analysis of liquid and solid fuels, see the documents referenced in the introduction 

to Section 4). 

( )( ) ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛ =

f

i

i f f MW

MW E Q C (Eq. 4-6) 

where (assuming gaseous fuel): 

 Ei = Emission estimate of pollutant “i” (lb/hr) 

 Qf = Fuel flow rate (scf/hr) 

 Cf = Content of pollutant in fuel (lb/scf) 

 MWi = Molecular weight of pollutant emitted (pounds per pound mole [lb/lb-mol]) 

 MWf = Molecular weight of pollutant in the fuel (lb/lb-mol) 

As previously explained, to calculate yearly emissions, this type of calculation must be repeated for each 

hour in the year, or 8,760 times. Also, as described in Example 4-1, if the combustion source did not 

operate for part of an hour, then the emission estimates for that hour should be multiplied by the fraction 

of the hour that it did operate. 

If the compound concentration is measured in parts per million or as a percentage rather than pounds per 

cubic feet, then Equation 4-7 will be needed. Equation 4-7 provides a methodology for calculating 

compound-specific conversion factors such as the values shown in Table 19-1 of EPA Method 19 for NOx

and SO2. 

( ) ( )

×385.3

× = K

C MW C c i

f (Eq. 4-7) 
Version 2.1.1 

Final ICR Version – Corrected Section 4—Stationary Combustion Sources 

4-10 

where: 

 Cf = Content of pollutant in fuel (lb/scf) 

 Cc = Volumetric concentration of pollutant in fuel (ppm or percentage) 

 MWi = Molecular weight of pollutant “i” emitted (lb/lb-mole) 

 K = Conversion constant: 106

 if units of Cc are ppm; 102 if units of Cc are a percentage 

 385.3 = Conversion constant for ideal gases (standard cubic feet per pound mole [scf/lb-mol]) 

4.4 Methodology Rank 3B for Stationary Combustion Sources 

Source testing can provide useful data for developing site-specific emission correlations or emission 

factors. Source testing provides a measurement of the emissions at a particular point in time, and most 

tests are performed at conditions representative of normal operation, in which case the emission 

measurement can provide an estimate of emissions at similar operating conditions. Emission factors are 

developed by dividing the emission rate by a process parameter such as fuel usage. It is important to note 

that this methodology will be less reliable when the unit is operating at conditions other than those tested. 

Generally, one source test consisting of three runs is performed at a specific set of conditions, and the 

results for each run can be averaged to determine an emission factor that is assumed to apply at all heat 

input rates. Example 4-5 demonstrates a sample emission factor calculation based on one test with three 

test runs. Section 5.1.2 of this document, Methodology Ranks 3 and 4 for Catalytic Cracking Units, also 

provides details on calculating one emission factor based on three test runs. That section also includes a 

Example 4-5: Fuel Analysis 

Calculate hourly emissions from a combustion source burning refinery fuel gas given: 

– Fuel flow rate = 500 dscfm, or 30,000 dscf/hr (500 dscfm × 60 min/hr) 

– Sulfur content of the fuel = 160 ppm 

– Molecular weight of sulfur = 32 lb/lb-mole; molecular weight of SO2 = 64 lb/lb-mole 

Convert the concentration of sulfur in the fuel to the correct units using Equation 4-7: 

( ) ( )

×385.3

× = K

C MW C c S

f

 Cf = (160) × (32) ÷ (106) ÷ (385.3) 

 Cf = 1.33 × 10-5 lb/scf 

Then, use Equation 4-6 to calculate the hourly mass emissions: 

( )( ) ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛ =

S

SO

SO f f MW

MW

E Q C 2

2

 ESO2 

= (30,000) × (1.33 × 10-5) × (64) ÷ (32) 

 ESO2 

= 0.80 lbs SO2/hr 

If the combustion source operated steadily and continuously for an entire year and the 

emissions rate remained perfectly constant over that year, then the annual emissions would be 

0.80 lbs/hr × 8,760 hr/yr ÷ 2,000 pounds per ton (lb/ton) = 3.5 tons/yr. 
Version 2.1.1 

Final ICR Version – Corrected Section 4—Stationary Combustion Sources 

4-11 

detailed description of the ways in which source tests and analyses for PM may need to be handled 

differently than other pollutants. 

A more complex methodology for developing a correlation rather than one emission factor is provided in 

Section 2.1.2 of A Customized Approach for Quantifying Emissions for the Electric Power Generation 

Sector in Mexico (The United States–Mexico Foundation for Science, 2008). Section 2.1.2 provides a 

detailed explanation of a methodology for developing a correlation between NOx emissions and heat input 

to the source (fuel use multiplied by heat content of fuel) that is based on EPA’s Optional NOx Emissions 

Estimation Protocol for Gas-Fired Peaking Units and Oil-Fired Peaking Units (40 CFR Part 75, 

Appendix E). This methodology allows the operator to account for lower mass emissions per heat input 

for lower operating loads. The methodology calls for stack measurements at three load levels, ideally 

50%, 75%, and 100% firing rates. The test results at each firing rate are used to calculate an emission 

factor in units of mass per heat input (or mass per amount of fuel combusted, assuming a constant heat 

content of fuel). Following the development of this correlation, hourly emissions can be calculated based 

on hourly measurements of fuel combusted and calculations of the heat content of the fuel (or constant 

heating value of the fuel). Section 2.1.2 also includes a detailed set of sample calculations in Exhibit 2.1-3 

to demonstrate this procedure. 

4.5 Methodology Rank 4 for Stationary Combustion Sources 

When direct emission monitoring or site-specific emission factors are not available, then default emission 

factors may be the only way to estimate emissions. The EPA has developed emission factors for various 

types of combustion sources, which are compiled in AP-42. Emission factors for process heaters, boilers, 

and other types of external combustion sources are included Chapter 1 of the Compilation of Air Pollutant 

Emission Factors. Volume 1: Stationary Point and Area Sources, and emission factors for internal 

combustion sources (including engines and combustion turbines) are presented in Chapter 3 of this same 

document (U.S. EPA, 1995a). It is important to note that AP-42 does not include emission factors for all 

fuels (notably refinery fuel gas and coke). The emission factors in AP-42 are the recommended default 

emission factors, and AP-42 should be consulted to obtain the appropriate emission factors for criteria 

pollutants such as SO2, NOx, PM, and CO. 

In addition, the American Petroleum Institute (API), in conjunction with the Western States Petroleum 

Association (WSPA), has conducted emission source tests of combustion sources and has compiled 

Example 4-6: Site-Specific Emissions Factor 

During the most recent source test, three test runs were conducted to determine the NOx

emission rate for a 50 MMBtu/hr process heater. The NOx emissions rate measured during the 

source tests were 1.92, 1.51, and 1.76 lbs/hr for tests 1, 2, and 3, respectively. The process 

heater was firing at 95% capacity during all three test runs. 

First, calculate the appropriate emissions factor for each individual run, and then average the 

emissions factors with the following calculations: 

– Run 1: Emissions/throughput = 1.92 [lbs/hr] ÷ (50 × 0.95) [MMBtu/hr] = 0.040 lbs 

NOx/MMBtu 

– Run 2: Emissions/throughput = 1.51 [lbs/hr] ÷ (50 × 0.95) [MMBtu/hr] = 0.032 lbs 

NOx/MMBtu 

– Run 3: Emissions/throughput = 1.76 [lbs/hr] ÷ (50 × 0.95) [MMBtu/hr] = 0.037 lbs 

NOx/MMBtu 

– Average: Emissions/throughput = (0.040 + 0.032 + 0.037) ÷ 3 = 0.036 lbs NOx/MMBtu 
Version 2.1.1 

Final ICR Version – Corrected Section 4—Stationary Combustion Sources 

4-12 

emission factors that may be used for refinery combustion sources if AP-42 does not include an 

applicable emission factor (Hansell and England, 1998). Separate emission factors were developed for 

different combustion sources based on the type of source and fuel used. Appendix D presents the full data 

analysis summary for combustion sources of interest as presented in Hansell and England’s Appendices A 

and B (1998), including the California Air Resources Board (CARB) emission factor rating; the mean, 

median, maximum, and minimum emission factors; number of tests analyzed; standard deviation; 

uncertainty; and percent of test run results at or above the detection limit. 

The following tables present the recommended emission factors for a variety of metals and organic 

compounds. The emission factors in these tables are either the applicable emission factors as presented in 

AP-42 or the mean emission factors compiled by Hansell and England (1998). (Additional details on the 

rating and quality of these emission factors are located in the original document for AP-42 emission 

factors and in Appendix D for the emission factors compiled by Hansell and England (1998).) Emission 

factors for boilers and process heaters using various fuels are presented in Table 4-3. Emission factors for 

reciprocating internal combustion engines using a variety of fuels are presented in Table 4-4. Emission 

factors for combustion turbines using a variety of fuels are presented in Table 4-5. 

To use any of these emission factors appropriately, the refinery must monitor or keep records of the 

amount of fuel combusted or the heat input. 

It is important to note that the bold italic emission factor values in Tables 4-3 through 4-5 from Hansell 

and England (1998) are based on method detection limits and are likely biased high. Additional data are 

needed to develop accurate emission factors for the compounds that were below the method detection 

limits (RTI, 2002). The footnotes to Tables 4-3 through 4-5 explain any differences if a recommended 

emission factor is derived from another emission factor. 

It is also important to note that this document does not include emission factors for refinery combustion 

sources combusting either green or calcined petroleum coke. In addition, while emissions from the 

combustion of syngas (gas produced by coke gasification) can be estimated using the methods provided in 

this section, this document does not include emission factors for syngas as a fuel. Emission factors for 

these fuels will need to be developed from future emission testing and analysis. 

4.5.1 Default Emission Factors for Process Heaters 

The emissions from boilers and process heaters were dependent on the fuel type: gas (i.e., natural gas or 

refinery gas), crude oil/pipeline oil, residual (No. 6) fuel oil, and distillate (No. 2) fuel oil. No distinctions 

in HAP emission factors were made for criteria pollutant controls, such as selective catalytic reduction 

(SCR), or selective non-catalytic reduction (SNCR). Table 4-3 presents a summary of emission factors 

for boilers and process heaters.
Version 2.1.1 

Final ICR Version – Corrected Section 4—Station

4-13 

Table 4-3. Summary of Emission Factors for Boilers and Process Heaters Firing Various Fuel

CAS 

Number Substance 

Emission Factor for Fuel Type a

External Combustion, 

Natural Gas/Refinery 

Gas (lb/MMBtu) b

External Combustion, 

Crude Oil/Pipeline Oil 

(lb/MMBtu) b

External Combustion, 

Residual Fuel Oil 

(No. 6 Oil) (lb/MMBtu) b

83-32-9 Acenaphthene 2.4E-09 1.7E-07 1.4E-07 f 

208-96-8 Acenaphthylene 6.5E-09 2.3E-08 1.7E-09 f 

75-07-0 Acetaldehyde 1.2E-05 1.1E-05 7.0E-06 

107-02-8 Acrolein 1.7E-05 3.3E-06 -- 120-12-7 Anthracene 4.7E-09 3.7E-08 8.1E-09 f 

7440-36-0 Antimony 5.2E-07 -- 3.5E-05 h 7440-38-2 Arsenic 2.0E-07 c 6.7E-06 8.8E-06 h 7440-39-3 Barium 4.3E-06 c -- 1.7E-05 h 

71-43-2 Benzene 2.1E-06 d 4.1E-06 1.4E-06 f 56-55-3 Benzo(a)anthracene 2.2E-08 3.2E-08 2.7E-08 f 50-32-8 Benzo(a)pyrene 5.7E-08 1.4E-08 1.4E-09 

205-99-2 Benzo(b)fluoranthene 2.7E-08 5.5E-09 9.9E-09 f, g 192-97-2 Benzo(e)pyrene -- 3.9E-09 5.8E-09 191-24-2 Benzo(g,h,i)perylene 1.3E-09 1.9E-08 1.5E-08 f 207-08-9 Benzo(k)fluoranthene 1.7E-08 2.3E-10 9.9E-09 f, g 

7440-41-7 Beryllium 1.3E-07 1.9E-06 1.9E-07 h 

106-99-0 1,3-Butadiene -- 1.4E-04 -- 106-97-8 Butane 2.1E-03 d -- -- 

7440-43-9 Cadmium 1.1E-06 c 2.2E-06 2.7E-06 h 

16887-00-6 Chloride -- -- 2.3E-03 h 

67-66-3 Chloroform -- 6.0E-05 3.4E-05 
Version 2.1.1 

Final ICR Version – Corrected Section 4—Station

4-14 

Table 4-3. Summary of Emission Factors for Boilers and Process Heaters Firing Various Fuels (con

CAS 

Number Substance 

Emission Factor for Fuel Type a

External Combustion, 

Natural Gas/Refinery 

Gas (lb/MMBtu) b

External Combustion, 

Crude Oil/Pipeline Oil 

(lb/MMBtu) b

External Combustion, 

Residual Fuel Oil 

(No. 6 Oil) (lb/MMBtu) b

91-58-7 2-Chloronaphthalene -- 8.2E-08 1.5E-10 

18540-29-9 Chromium (hexavalent) 2.8E-07 l 1.1E-06 1.7E-06 h 

7440-47-3 Chromium (total) 1.4E-06 c 8.7E-06 5.6E-06 h 

218-01-9 Chrysene 1.6E-09 7.5E-08 1.6E-08 f 

7440-48-4 Cobalt 8.2E-08 c -- 4.0E-05 h 7440-50-8 Copper 8.3E-07 c 9.5E-06 1.2E-05 h 

53-70-3 Dibenz(a,h)anthracene 1.2E-09 d 1.2E-08 1.1E-08 f 

25321-22-6 Dichlorobenzene 1.2E-06 d -- -- 

57-97-6 7,12-Dimethylbenz(a) anthracene 1.6E-08 d -- -- 

1746-01-6 Dioxin: 4D 2378j -- 3.5E-12 4.3E-12 

40321-76-4 Dioxin: 5D 12378j -- 1.7E-11 2.5E-12 39227-28-6 Dioxin: 6D 123478j -- 1.5E-11 2.5E-12 57653-85-7 Dioxin: 6D 123678j -- 2.1E-11 2.5E-12 19408-74-3 Dioxin: 6D 123789j -- 3.3E-11 2.5E-12 35822-46-9 Dioxin: 7D 1234678j -- 9.3E-11 2.1E-11 

3268-87-9 Dioxin: 8Dj -- 3.3E-10 2.1E-11 f 

74-84-0 Ethane 3.0E-03 d -- -- 

100-41-4 Ethylbenzene 1.6E-05 -- 4.2E-07 f 206-44-0 Fluoranthene 2.9E-09 d 6.9E-08 3.2E-08 f 

86-73-7 Fluorene 2.7E-09 d 2.0E-07 3.0E-08 f 
Version 2.1.1 

Final ICR Version – Corrected Section 4—Station

4-15 

Table 4-3. Summary of Emission Factors for Boilers and Process Heaters Firing Various Fuels (con

CAS 

Number Substance 

Emission Factor for Fuel Type a

External Combustion, 

Natural Gas/Refinery 

Gas (lb/MMBtu) b

External Combustion, 

Crude Oil/Pipeline Oil 

(lb/MMBtu) b

External Combustion, 

Residual Fuel Oil 

(No. 6 Oil) (lb/MMBtu) b

16984-48-8 Fluoride -- -- 2.5E-04 h 

50-00-0 Formaldehyde 7.4E-05 d 1.1E-05 2.2E-04 f 

51207-31-9 Furan: 4F 2378k -- 6.2E-10 5.5E-12 57117-41-6 Furan: 5F 12378k -- 6.0E-11 3.1E-12 57117-31-4 Furan: 5F 23478k -- 1.1E-10 3.1E-12 70648-26-9 Furan: 6F 123478k -- 1.3E-10 2.5E-12 57117-44-9 Furan: 6F 123678k -- 4.3E-11 1.9E-12 72918-21-9 Furan: 6F 123789k -- 3.5E-12 2.5E-12 60851-34-5 Furan: 6F 234678k -- 6.1E-11 3.7E-12 67562-39-4 Furan: 7F 1234678k -- 1.4E-10 9.8E-12 55673-89-7 Furan: 7F 1234789k -- 8.3E-12 3.2E-12 39001-02-0 Furan: 8Fk -- 7.3E-11 4.9E-11 

110-54-3 Hexane 1.8E-03 d -- -- 

7783-06-4 Hydrogen sulfide 8.5E-05 -- -- 

193-39-5 Indeno(1,2,3-cd)pyrene 7.1E-08 1.9E-08 1.4E-08 f 

7439-92-1 Lead 4.9E-07 e 1.9E-06 1.0E-05 h 7439-96-5 Manganese 3.7E-07 c 1.8E-05 2.0E-05 h 7439-97-6 Mercury 2.5E-07 c 1.0E-05 7.5E-07 h 

56-49-5 3-Methylchloranthrene 1.8E-09 d -- -- 91-57-6 2-Methylnaphthalene 2.4E-08 d 2.5E-07 7.4E-08 

7439-98-7 Molybdenum 1.1E-06 c -- 5.2E-06 h 
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Table 4-3. Summary of Emission Factors for Boilers and Process Heaters Firing Various Fuels (con

CAS 

Number Substance 

Emission Factor for Fuel Type a

External Combustion, 

Natural Gas/Refinery 

Gas (lb/MMBtu) b

External Combustion, 

Crude Oil/Pipeline Oil 

(lb/MMBtu) b

External Combustion, 

Residual Fuel Oil 

(No. 6 Oil) (lb/MMBtu) b

91-20-3 Naphthalene 6.0E-07 d 5.5E-06 7.5E-06 f 

7440-02-0 Nickel 2.1E-06 c 2.4E-03 5.6E-04 h 

109-66-0 Pentane 2.5E-03 -- -- 198-55-0 Perylene -- 5.2E-10 7.4E-10 

85-01-8 Phenanthrene 1.7E-08 d 1.7E-07 7.0E-08 f 

108-95-2 Phenol 4.0E-06 -- -- 

7723-14-0 Phosphorus 6.4E-07 1.8E-04 6.3E-05 h 

74-98-6 Propane 1.6E-03 d -- -- 

115-07-1 Propylene 1.5E-04 4.4E-05 -- 129-00-0 Pyrene 4.9E-09 d 1.2E-07 2.8E-08 f 

7782-49-2 Selenium 8.8E-07 7.9E-06 4.5E-06 h 

71-55-6 1,1,1-Trichloroethane -- -- 1.6E-06 f 

108-88-3 Toluene 3.3E-06 d 3.5E-05 4.1E-05 f 

7440-62-2 Vanadium 2.3E-06 c -- 2.1E-04 h 

95-47-6 Xylene (o) -- -- 7.3E-06 f 

1330-20-7 Xylene (total) 2.5E-05 2.9E-06 -- 7440-66-6 Zinc 2.8E-05 c 4.2E-04 1.9E-04 h 
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Table 4-3. Summary of Emission Factors for Boilers and Process Heaters Firing Various Fuels (con

Note: lb/MMBtu = pounds per million British thermal units a Bold italic values indicate that all test runs were below detection limit; underlined values indicate that 75% or more of the test runs we

limit. 

b Source: Hansell and England, 1998, unless otherwise specified. c Source: U.S. EPA, 1995a, AP-42 Section 1.4, Table 1.4-4. Emission factors were provided for natural gas combustion sources. Value

scf to lb/MMBtu by dividing by 1,020 MMBtu/106 scf. 

d Source: U.S. EPA, 1995a, AP-42 Section 1.4, Table 1.4-3. Emission factors were provided for natural gas combustion sources. Value

scf to lb/MMBtu by dividing by 1,020 MMBtu/106 scf. 

e Source: U.S. EPA, 1995a, AP-42 Section 1.4, Table 1.4-2. Emission factors were provided for natural gas combustion sources. Value

scf to lb/MMBtu by dividing by 1,020 MMBtu/106 scf. 

f Source: U.S. EPA, 1995a, AP-42 Section 1.3, Table 1.3-9. Emission factors were provided specifically for residual oil (No. 6 oil) fired 

from lb/103 Gal to lb/MMBtu by dividing by 150 MMBtu/103 Gal. 

g Emission factor includes both benzo(b)fluoranthene and benzo(k)fluoranthene. h Source: U.S. EPA, 1995a, AP-42 Section 1.3, Table 1.3-11. Emission factors were provided specifically for residual oil (No. 6 oil) fired 

converted from lb/103 Gal to lb/MMBtu by dividing by 150 MMBtu/103 Gal. 

i Source: U.S. EPA, 1995a, AP-42 Section 1.3, Table 1.3-10. Emission factors were provided specifically for distillate oil-fired boilers. V

lb/1012 Btu to lb/MMBtu by dividing by 106. 

j 4D 2378 = 2,3,7,8-Tetrachlorodibenzo-p-dioxin; 5D 12378 = 1,2,3,7,8-Pentachlorodibenzo-p-dioxin; 6D 123478 = 1,2,3,4,7,8-Hexach

123678 = 1,2,3,6,7,8-Hexachlorodibenzo-p-dioxin; 6D 123789 = 1,2,3,7,8,9-Hexachlorodibenzo-p-dioxin; 7D 1234678 = 1,2,3,4,6,7,8

dioxin; 8D = Octachlorodibenzo-p-dioxin. 

k 4F 2378 = 2,3,7,8-Tetrachlorodibenzofuran; 5F 12378 = 1,2,3,7,8-Pentachlorodibenzofuran; 5F 23478 = 2,3,4,7,8-Pentachlorodibenz

1,2,3,4,7,8-Hexachlorodibenzofuran; 6F 123678 = 1,2,3,6,7,8-Hexachlorodibenzofuran; 6F 123789 = 1,2,3,7,8,9-Hexachlorodibenzof

2,3,4,6,7,8-Hexachlorodibenzofuran; 7F 1234678 = 1,2,3,4,6,7,8-Heptachlorodibenzofuran; 7F 1234789 = 1,2,3,4,7,8,9-Heptachlorod

Octachlorodibenzofuran. 

l Hexavalent chromium was not detected. Twenty percent of the total chromium emission factor is assumed for the hexavalent chromiu

hexavalent chromium emission factors for gas turbines are between 10 and 15 percent of the total chromium emission factor, and the emission factor for boilers firing fuel oil is about 30 percent of the total chromium emission factor (based on detection limits, which are 

hexavalent chromium emissions), so 20 percent is a conservative (reasonable high-end) estimate for hexavalent chromium emission
Version 2.1.1 

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4-18 

4.5.2 Default Emission Factor for Internal Combustion Engines 

The emissions from reciprocating internal combustion engines were dependent on: (1) the type of fuel 

used (diesel fuel, or gas [field gas, or natural gas]), (2) the type of engine used (two-stroke versus fourstroke engines), and (3) the fuel-to-air ratio. As shown in Table 4-4, high air rates (or lean fuel mixtures) 

tend to have higher emissions of acetaldehyde and formaldehyde, whereas lean gas mixtures tend to have 

higher emissions of benzene, toluene, and xylenes. 

4.5.3 Default Emission Factors for Combustion Turbines 

The emissions from combustion turbines were dependent on (1) the type of fuel used (e.g., distillate fuel 

oil, or gas [refinery fuel gas, liquefied petroleum gas, or natural gas]), and (2) the presence or absence of 

duct burners. No distinctions in HAP emission factors were made for criteria pollutant controls, such as 

selective catalytic reduction (SCR), or carbon monoxide oxidation catalyst. Table 4-5 presents a 

summary of emission factors for combustion turbines. 
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Table 4-4. Summary of Emission Factors for Internal Combustion Engines Firing Various Fuel

CAS 

Number Substance 

Emission Factor for Engine and Fuel Type b

Diesel, 

O2 < 13% 

(lb/MMBtu) 

Diesel, 

O2 > 13% 

(lb/MMBtu) 

Diesel, 

O2 not specified 

(lb/MMBtu) c

Natural Gas/Field 

Gas, 

Lean (2-Stroke) 

(lb/MMBtu) d

Natura

Gas/Field 

Lean (4-Str

(lb/MMBt

83-32-9 Acenaphthene 4.5E-06 1.4E-06 < 1.4E-06 f 1.3E-06 g 1.3E-06 

208-96-8 Acenaphthylene 9.0E-06 5.1E-06 < 5.1E-06 f 3.2E-06 g 5.5E-06 

75-07-0 Acetaldehyde 2.4E-05 7.6E-04 7.7E-04 7.8E-03 8.4E-03 

107-02-8 Acrolein 7.6E-06 9.4E-05 < 9.3E-05 7.8E-03 5.1E-03 120-12-7 Anthracene 1.2E-06 1.9E-06 1.9E-06 f 7.2E-07 g 2.4E-07 100-52-7 Benzaldehyde -- 9.0E-05 -- -- -- 

71-43-2 Benzene 7.1E-04 8.8E-04 9.3E-04 1.9E-03 4.4E-04 56-55-3 Benzo(a)anthracene 6.1E-07 1.7E-06 1.7E-06 f 3.4E-07 g 7.4E-08 50-32-8 Benzo(a)pyrene 2.5E-07 1.0E-08 < 1.9E-07 f 5.7E-09 g 3.4E-08 

205-99-2 Benzo(b)fluoranthene 1.1E-06 1.9E-07 < 9.9E-08 f 8.5E-09 g 1.7E-07 192-97-2 Benzo(e)pyrene -- -- -- 2.3E-08 g 4.2E-07 191-24-2 Benzo(g,h,i)perylene 5.4E-07 4.1E-07 < 4.9E-07 f 2.5E-08 g 4.1E-07 207-08-9 Benzo(k)fluoranthene 2.1E-07 3.0E-07 < 1.6E-07 f 4.3E-09 g 5.0E-07 

92-52-4 Biphenyl -- -- -- 4.0E-06 2.1E-04 

106-99-0 1,3-Butadiene -- 3.9E-05 < 3.9E-05 8.2E-04 2.7E-04 106-97-8 Butane -- -- -- 4.8E-03 5.4E-04 

 Butyr/Isobutyraldehyde -- -- -- 4.4E-04 1.0E-04 

56-23-5 Carbon tetrachloride -- -- -- 6.1E-05 < 3.7E-0

108-90-7 Chlorobenzene -- -- -- 4.4E-05 < 3.0E-0

75-00-3 Chloroethane -- -- -- -- 1.9E-06 
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Table 4-4. Summary of Emission Factors for Internal Combustion Engines Firing Various Fuelsa (con

CAS 

Number Substance 

Emission Factor for Engine and Fuel Type b

Diesel, 

O2 < 13% 

(lb/MMBtu) 

Diesel, 

O2 > 13% 

(lb/MMBtu) 

Diesel, 

O2 not specified 

(lb/MMBtu) c

Natural Gas/Field 

Gas, 

Lean (2-Stroke) 

(lb/MMBtu) d

Natura

Gas/Field 

Lean (4-Str

(lb/MMBt

67-66-3 Chloroform -- -- -- 4.7E-05 < 2.9E-0

218-01-9 Chrysene 1.5E-06 3.5E-07 3.5E-07 f 6.7E-07 g 6.9E-07 110-82-7 Cyclohexane -- -- -- 3.1E-04 -- 287-92-3 Cyclopentane -- -- -- 9.5E-05 2.3E-04 

53-70-3 Dibenz(a,h)anthracene 3.4E-07 4.1E-07 < 5.8E-07 f -- g 1.0E-08 75-34-3 1,1-Dichloroethane -- -- -- 3.9E-05 < 2.4E-0

107-06-2 1,2-Dichloroethane -- -- -- 4.2E-05 < 2.4E-0

78-87-5 1,2-Dichloropropane -- -- -- 4.5E-05 < 2.7E-0

542-75-6 1,3-Dichloropropene -- -- -- 4.4E-05 < 2.6E-0

74-84-0 Ethane -- -- -- 7.1E-02 1.1E-01 

100-41-4 Ethylbenzene -- -- -- 1.1E-04 4.0E-05 106-93-4 Ethylene dibromide -- -- -- 7.3E-05 < 4.4E-0206-44-0 Fluoranthene 3.9E-06 7.6E-06 7.6E-06 f 3.6E-07 g 1.1E-06 

86-73-7 Fluorene 1.2E-05 2.9E-05 2.9E-05 f 1.7E-06 g 5.7E-06 50-00-0 Formaldehyde 7.7E-05 1.2E-03 1.2E-03 5.5E-02 5.3E-02 

110-54-3 n-Hexane -- -- -- 4.5E-04 1.1E-03 193-39-5 Indeno(1,2,3-cd)pyrene 4.0E-07 2.7E-07 < 3.8E-07 f 9.9E-09 g 1.1E-07 

75-28-5 Isobutane -- -- -- 3.8E-03 -- 67-56-1 Methanol -- -- -- 2.5E-03 2.5E-03 

108-87-2 Methylcyclohexane -- -- -- 3.4E-04 1.2E-03 
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Table 4-4. Summary of Emission Factors for Internal Combustion Engines Firing Various Fuelsa (con

CAS 

Number Substance 

Emission Factor for Engine and Fuel Type b

Diesel, 

O2 < 13% 

(lb/MMBtu) 

Diesel, 

O2 > 13% 

(lb/MMBtu) 

Diesel, 

O2 not specified 

(lb/MMBtu) c

Natural Gas/Field 

Gas, 

Lean (2-Stroke) 

(lb/MMBtu) d

Natura

Gas/Field 

Lean (4-Str

(lb/MMBt

75-09-2 Methylene chloride -- -- -- 1.5E-04 2.0E-05 91-57-6 2-Methylnaphthalene -- -- -- 2.1E-05 g 3.3E-05 91-20-3 Naphthalene 1.3E-04 8.5E-05 8.5E-05 f 9.6E-05 g 7.4E-05 

111-84-2 n-Nonane -- -- -- 3.1E-05 1.1E-04 111-65-9 n-Octane -- -- -- 7.4E-05 3.5E-04 109-66-0 n-Pentane -- -- -- 1.5E-03 2.6E-03 198-55-0 Perylene -- -- -- 5.0E-09 g -- h 

85-01-8 Phenanthrene 4.0E-05 2.9E-05 2.9E-05 f 3.5E-06 g 1.0E-05 

108-95-2 Phenol -- -- -- 4.2E-05 2.4E-05 

74-98-6 Propane -- -- -- 2.9E-02 4.2E-02 

115-07-1 Propylene 2.7E-03 2.6E-03 2.6E-03 2.4E-02 a 1.7E-02 129-00-0 Pyrene 3.6E-06 4.8E-06 4.8E-06 f 5.8E-07 g 1.4E-06 100-42-5 Styrene -- -- -- 5.5E-05 < 2.4E-0

79-34-5 1,1,2,2-Tetrachloroethane -- -- -- 6.6E-05 < 4.0E-0

108-88-3 Toluene 2.6E-04 4.0E-04 4.1E-04 9.6E-04 4.1E-04 

79-00-5 1,1,2-Trichloroethane -- -- -- 5.3E-05 < 3.2E-0

526-73-8 1,2,3-Trimethylbenzene -- -- -- 3.5E-05 2.3E-05 

95-63-6 1,2,4-Trimethylbenzene -- -- -- 1.1E-04 1.4E-05 

108-67-8 1,3,5-Trimethylbenzene -- -- -- 1.8E-05 3.4E-05 540-84-1 2,2,4-Trimethylpentane -- -- -- 8.5E-04 2.5E-04 
Version 2.1.1 

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Table 4-4. Summary of Emission Factors for Internal Combustion Engines Firing Various Fuelsa (con

CAS 

Number Substance 

Emission Factor for Engine and Fuel Type b

Diesel, 

O2 < 13% 

(lb/MMBtu) 

Diesel, 

O2 > 13% 

(lb/MMBtu) 

Diesel, 

O2 not specified 

(lb/MMBtu) c

Natural Gas/Field 

Gas, 

Lean (2-Stroke) 

(lb/MMBtu) d

Natura

Gas/Field 

Lean (4-Str

(lb/MMBt

75-01-4 Vinyl chloride -- -- -- 2.5E-05 1.5E-05 

108-38-3, 

106-42-3 Xylene (m,p) -- 1.5E-04 -- 5.8E-04 a 1.4E-04 

95-47-6 Xylene (o) -- 1.5E-04 -- 2.7E-04 a 5.9E-05 

1330-20-7 Xylene (total) 1.9E-04 2.6E-04 2.9E-04 2.7E-04 1.8E-04 

Note: lb/MMBtu = pounds per million British thermal units a Source: Hansell and England, 1998, unless otherwise specified. b Bold italic values indicate that all test runs were below detection limit. c Source: U.S. EPA, 1995a, AP-42 Section 3.3, Table 3.3-2. Emission factors are for uncontrolled sources. Emission factors preceded w

are based on method detection limits. Note that these emission factors are for diesel engines up to 600 hp. Emission factors for diese

600 hp can be found in AP-42 Section 3.4. 

d Source: U.S. EPA, 1995a, AP-42 Section 3.2, Table 3.2-1. Emission factors are for uncontrolled sources. e Source: U.S. EPA, 1995a, AP-42 Section 3.2, Table 3.2-2. Emission factors are for uncontrolled sources. Emission factors preceded w

are based on method detection limits. 

f The emission factor for total polycyclic aromatic hydrocarbons (PAH) in U.S. EPA, 1995a, Table 3.3-2 is 1.7E-04 lb/MMBtu. g The emission factor for total PAH in U.S. EPA, 1995a, Table 3.2-1 is 1.3E-04 lb/MMBtu. h The emission factor for total PAH in U.S. EPA, 1995a, Table 3.2-2 is 2.7E-05 lb/MMBtu. i The emission factor for total PAH in U.S. EPA, 1995a, Table 3.2-3 is 1.4E-04 lb/MMBtu. j Source: U.S. EPA, 1995a, AP-42 Section 3.2, Table 3.2-3. Emission factors are for uncontrolled sources. Emission factors preceded w

are based on method detection limits.
Version 2.1.1 

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Table 4-5. Summary of Emission Factors for Combustion Turbines Firing Various Fuelsa

CAS Number Substance 

Emission Factors for Combustion Turbine and Fuel Ty

Distillate Oil, Type 

not specified 

(lb/MMBtu) c

Natural Gas, Type 

not specified 

(lb/MMBtu) d

Natural Gas/Refinery 

Fuel Gas/Liquefied 

Petroleum Gas, Duct 

Burners (lb/MMBtu) 

N

G

83-32-9 Acenaphthene -- e -- f 2.2E-08 

208-96-8 Acenaphthylene -- e -- f 1.1E-08 

75-07-0 Acetaldehyde -- 4.0E-05 4.1E-06 

107-02-8 Acrolein -- 6.4E-06 -- 120-12-7 Anthracene -- e -- f 2.5E-08 

7440-38-2 Arsenic < 1.1E-05 -- -- 

71-43-2 Benzene 5.5E-05 1.2E-05 -- 56-55-3 Benzo(a)anthracene -- e -- f 1.5E-08 50-32-8 Benzo(a)pyrene -- e -- f -- 

205-99-2 Benzo(b)fluoranthene -- e -- f 2.5E-08 191-24-2 Benzo(g,h,i)perylene -- e -- f -- 207-08-9 Benzo(k)fluoranthene -- e -- f -- 

7440-41-7 Beryllium < 3.1E-07 -- -- 

106-99-0 1,3-Butadiene < 1.6E-05 < 4.3E-07 -- 

7440-43-9 Cadmium 4.8E-06 -- 2.9E-06 

18540-29-9 Chromium (hexavalent) 2.2E-06 g -- 7.0E-06 

7440-47-3 Chromium (total) 1.1E-05 -- 5.0E-05 

218-01-9 Chrysene -- e -- f 1.1E-07 

7440-50-8 Copper -- -- 1.2E-05 

53-70-3 Dibenz(a,h)anthracene -- e -- f -- 
Version 2.1.1 

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4-24 

Table 4-5. Summary of Emission Factors for Combustion Turbines Firing Various Fuelsa (contin

CAS Number Substance 

Emission Factors for Combustion Turbine and Fuel Ty

Distillate Oil, Type 

not specified 

(lb/MMBtu) c

Natural Gas, Type 

not specified 

(lb/MMBtu) d

Natural Gas/Refinery 

Fuel Gas/Liquefied 

Petroleum Gas, Duct 

Burners (lb/MMBtu) 

N

G

100-41-4 Ethylbenzene -- 3.2E-05 -- 206-44-0 Fluoranthene -- e -- f 9.9E-08 

86-73-7 Fluorene -- e -- f 1.8E-07 50-00-0 Formaldehyde 2.8E-04 7.1E-04 3.1E-03 

7783-06-4 Hydrogen sulfide -- -- -- 

193-39-5 Indeno(1,2,3-cd)pyrene -- e -- f -- 

7439-92-1 Lead 1.4E-05 -- 3.6E-05 7439-96-5 Manganese 7.9E-04 -- 4.8E-05 7439-97-6 Mercury 1.2E-06 -- 4.4E-06 

91-20-3 Naphthalene 3.5E-05 e 1.3E-06 f 3.7E-05 

7440-02-0 Nickel < 4.6E-06 -- 7.7E-05 

85-01-8 Phenanthrene -- e -- f 6.4E-07 

108-95-2 Phenol -- -- 2.2E-05 115-07-1 Propylene -- -- -- 129-00-0 Pyrene -- e -- f 1.2E-07 

7782-49-2 Selenium < 2.5E-05 -- -- 

108-88-3 Toluene -- 1.3E-04 1.6E-04 

1330-20-7 Xylene (total) -- 6.4E-05 3.7E-04 7440-66-6 Zinc -- -- 1.2E-04 
Version 2.1.1 

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4-25 

Table 4-5. Summary of Emission Factors for Combustion Turbines Firing Various Fuelsa (contin

Note: lb/MMBtu = pounds per million British thermal units a Source: Hansell and England, 1998, Volume 1, unless otherwise specified. b Bold italic values indicate that all test runs were below detection limit. c Source: U.S. EPA, 1995a, Section 3.1, Table 3.1-4 and Table 3.1-5. Emission factors are based on an average distillate oil heating va

MMBtu/103 gal. 

d Source: U.S. EPA, 1995a, Section 3.1, Table 3.1-3. Emission factors are based on an average natural gas heating value (HHV) of 1,0e The emission factor for total polycyclic aromatic hydrocarbons (PAH) is 4.0E-05 lb/MMBtu. f The emission factor for total PAH is 2.2E-06 lb/MMBtu. g Hexavalent chromium is assumed to be twenty percent of the total chromium emission factor for the hexavalent chromium emission fa

chromium emission factors for boilers firing fuel oil is about 30 percent of the total chromium emission factor (based on detection limit

overstate hexavalent chromium emissions) and 18 percent of the total chromium for oil-fired utilities (U.S. EPA, 1998c), so 20 percen

reasonable approximation for hexavalent chromium emissions from distillate oil-fired combustion turbines. 
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[This page intentionally left blank.] 
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Final ICR Version – Corrected Section 5—Process Vents 

5-1 

5. Process Vents 

There are a variety of processes and equipment at petroleum refineries that may release pollutants directly 

into the atmosphere through process vents. Many of these process vents may be controlled using a flare, 

thermal incinerator, or other air pollution control techniques. This section describes the key process vents 

and emissions estimation procedures considering controls. At some facilities, the process gases may be 

routed to the refinery’s fuel gas system rather than directly to a control device to the atmosphere. These 

gases would then be combusted with the fuel gas in either a stationary combustion unit (process heater or 

boiler) or in a flare. As such, emissions from these gases are expected to be included in the emissions 

estimated for stationary combustion sources (see Section 4) or for flares (see Section 6). The methods in 

this section should be used for process vent gases other than those recovered into the refinery’s fuel gas 

system. Particularly, this section provides methods for estimating the emissions associated with catalytic 

cracking units (CCUs), coking units, CRUs, sulfur recovery plants, and other process vents (e.g., from 

hydrogen (H2) plants, asphalt blowing stills, coke calcining units, blowdown system, and vacuum 

generating units). 

Table 5-1 summarizes the general hierarchy of process vent emissions measurement or estimation 

methods, which are ranked in terms of anticipated accuracy. Within a given measurement method (or 

rank), there may be alternative methods for determining the constituent-specific emissions. Methodology 

Ranks 1 and 2 for process vents (i.e., the use of CEMS) have been previously described in Section 4, 

Stationary Combustion Sources. Although Section 5 will note these methods, where applicable, for 

individual process vents, Section 4 should be reviewed for sample calculations and other important 

considerations when using CEMS to determine mass emissions rates. 

Table 5-1. Summary of Typical Hierarchy of Process Vent Emissions Estimates 

Rank Flow Estimate Method Compositional Analysis Data 

1 Continuous flow meter Continuous gas composition analyzer 

2 Engineering estimates (e.g., F factor) Continuous gas composition analyzer 

3 Continuous flow meter or engineering estimates Occasional grab samples 

4 Measured process rates Site-specific emissions factor based on source test 

5 Measured process rates Default emissions factors 

5.1 Catalytic Cracking Units 

The CCU catalyst regenerator vent is often the single largest emissions vent at the refinery. The CCU is a 

catalytic process used to upgrade (crack) heavy distillates to form lighter, more useful distillates such as 

heating oils or gasoline. The CCU system consists of a reactor, a catalyst regenerator (commonly referred 

to as the “regenerator”), vent gas process equipment for energy recovery and emissions control, and an 

exhaust stack. Nearly all refinery CCU systems operate as fluidized-bed reactors and use air or oil gas 

flow to transport the very small catalyst particles between the CCU reactor and regenerator. These 

fluidized CCU systems are commonly referred to as fluid catalytic cracking units (FCCU). There are two 

or three refineries that use larger catalyst pellets in moving bed-type reactor system, which is commonly 

referred to as a thermal catalytic cracking unit (TCCU). Nearly all of the available emissions data are 

specific to FCCU, although data for PM, SO2 and NOX emissions are available for one TCCU. The 

emissions from the TCCU, when normalized on the basis of the coke burn-off rate, are similar to those of 

a similarly operated (uncontrolled) FCCU. Consequently, while the emissions inventory methods 

presented in this section are based primarily on FCCU operation and emissions data, these emissions 

inventory methods should be used for TCCU systems unless direct emissions data are available. 
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The CCU catalyst regenerator vent releases a wide variety of pollutants, including PM, SO2, NOx, carbon 

monoxide (CO), VOC, metal HAP, organic HAP, and ammonia. As a by-product of the cracking 

reactions, coke is deposited on the catalyst particles. The coke reduces the activity of the catalyst, and the 

spent catalyst that is returned from the CCU reactor is regenerated continuously by burning off coke in 

the CCU catalyst regenerator. There are two basic types of CCU regenerators: complete combustion 

regenerators and partial combustion regenerators. In a complete combustion regenerator, the regenerator 

is typically operated at approximately 1,200°F to 1,400°F with excess O2 and low levels (< 500 ppmv) of 

CO in the exhaust flue gas. In a partial (or incomplete) combustion regenerator, the regenerator is 

typically operated at approximately 1,000°F to 1,200°F under O2-limited conditions and relatively high 

levels (1% to 5%) of CO. Prior to exiting the regenerator, catalyst particles entrained with the flue gases 

are initially removed by internal cyclone separators and returned to the regenerator catalyst bed for 

recirculation to the reactor. 

On a routine basis, a small portion of the circulating catalyst, commonly referred to as equilibrium 

catalyst (E-cat), is removed from the system and fresh catalyst is added to maintain catalyst activity and 

replace catalyst lost or removed from the system. Various other additives may also be included with the 

catalyst additions to reduce NOx or SO2 emissions or promote complete combustion (thereby reducing CO 

emissions). Although the CCU vent is the primary emissions source associated with the CCU, fugitive 

dust emissions associated with handling the fresh catalyst or spent E-cat should also be calculated and 

included in the emissions inventory for CCU systems. 

After the flue gas exits the CCU regenerator, a variety of energy recovery or emissions control systems 

may be used to reduce pollutant releases. For a complete combustion CCU, a waste heat boiler is often 

used to recover the latent heat of the flue gas. The energy recovery system also serves to cool the flue gas 

prior to PM or other add-on control systems. The most common control systems for CCU are electrostatic 

precipitators (ESP) or wet scrubbers. For a partial combustion CCU, the first control system is typically a 

CO boiler used to combust the CO in the flue gas to CO2 and recover the heat of combustion and latent 

heat of the flue gas (typically by producing steam). 

5.1.1 Methodology Ranks 1 and 2 for Catalytic Cracking Units 

For SO2, NOx, CO, and VOC, it is anticipated that many CCUs will have CEMS for measuring the 

composition of these pollutants in the exhaust gas. Although few CCUs are expected to have PM CEMS, 

if PM CEMS are used, these measurements would are also qualify as Methodology Rank 1 or 2 for CCUs 

even though some “PM augmentation” will be needed as described in Sections 5.1.2.1 and 5.1.2.2. 

Similarly, if CEMS are used for specific HAPs, these measurements should be used and reported as 

Methodology Rank 1 or 2 for CCUs. Gas flow rate may be directly monitored, but in many cases, the 

exhaust flow rate will be calculated based on air blast rates and composition monitors (similar to F factors 

based on coke burn-off rates). Equations in 40 CFR Part 63 Subpart UUU can be used to estimate flow 

rates based on gas composition analyzers that are typically used to monitor the regenerator combustion 

parameters. When CEMS or direct-flow monitors are present, these data should be used to calculate 

annual pollutant emissions. 

5.1.2 Methodology Ranks 3 and 4 for Catalytic Cracking Units 

For VOC, PM, and specific HAP, it is anticipated that many refineries will have performed source tests of 

their CCUs. Generally, testing will be conducted infrequently so the testing results represent an emissions 

rate at a given point in time and production level. Rather than assuming that the mass emissions rate 

measured during the test occurs continuously for all process operating hours, the resulting source test data 

are most appropriately used for developing a site-specific emissions factor. This type of emissions factor 

is the measured emissions rate (lb/hr) divided by the processing rate (throughput per hr). Generally, the 

emissions from the CCU catalyst regenerator vent are best correlated with coke burn-off rates; however, if 

CCU feed and operating conditions do not vary significantly, then throughput-based emissions factors 
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may be used. If multiple tests have been conducted on the CCU and no significant modifications have 

been made on the CCU or its control system, then an arithmetic average of the emission factors should be 

used to estimate annual average emissions. If modifications have been made on the CCU or its control 

system, the most recently performed source test should be used to develop the site-specific emissions 

factor. To estimate maximum hourly emissions, the highest emission factor developed from the individual 

runs should be used along with the maximum capacity (or coke burn-off rate) of the CCU. 

Although site-specific emissions factors can be developed for PM, VOC, organic HAP species, or metal 

HAP species using source test data, there are some unique nomenclature and reporting practices for PM 

emissions that deserve additional guidance. Additionally, a quasi Methodology Rank 4 for CCU metal 

Example 5-1: Development of Site-Specific Emissions Factor 

A source test was performed to determine the PM emissions rate from a CCU. Three test runs 

were conducted; the PM emissions rates measured during the three test runs were 20.2, 25.1, 

and 17.6 lb/hr for tests 1, 2, and 3, respectively. The processing rates during the three runs were 

1,600; 1,700; and 1,500 barrels per hour (bbl/hr) and the coke burn-off rates were 25,000; 

29,000; and 23,000 lb/hr for tests 1, 2, and 3, respectively. An appropriate emissions factor for 

the CCU can be developed to project annual emissions. 

First, the emissions factor for each individual run should be calculated, and then the emissions 

factors should be averaged. Emissions factors can be assessed using different normalizing 

factors, such as throughput and coke burn-off rates, as follows: 

– Run 1: Emissions/throughput = 20.2 (lb/hr) ÷ 1,600 (bbls/hr) = 0.0126 lb/bbl = 12.6 pounds per 

thousands of barrels (lb/Mbbl) 

Emissions/coke burn-off = 20.2 (lb/hr) ÷ 25 (1,000 lb/hr) = 0.808 lb/1,000 lbs coke burn-off 

– Run 2: Emissions/throughput = 25.1 (lb/hr) ÷ 1.7 (Mbbl/hr) = 14.8 lb/Mbbl 

Emissions/coke burn-off = 25.1 (lb/hr) ÷ 29 (1,000 lb/hr) = 0.866 lb/1,000 lbs coke burn-off 

– Run 3: Emissions/throughput = 17.6 (lb/hr) ÷ 1.5 (Mbbl/hr) = 11.7 lb/Mbbl 

Emissions/coke burn-off = 17.6 (lb/hr) ÷ 23 (1,000 lb/hr) = 0.765 lb/1,000 lbs coke burn-off 

– Average: Emissions/throughput = (12.6 + 14.8 + 11.7) ÷ 3 = 13.0 lb/Mbbl 

Emissions/coke burn-off = (0.808 + 0.866 + 0.765) ÷ 3 = 0.813 lb/1,000 lb coke burn-off 

There are a variety of ways to determine which emissions factor is most appropriate. One 

method is to compare the range of the test runs compared to the three-run average. For the 

throughput-based emissions factors, the highest single-run emissions factor is 14% (100% × 

[14.8 − 13] ÷ 13) higher than the average, and the lowest single-run emissions factor is 10% 

lower than the average. For the coke burn-off rate emissions factors, the highest single-run 

emissions factor is 6.5% (100% × [0.866 − 0.813] ÷ 0.813) higher than the average, and the 

lowest single-run emissions factor is 5.9% lower than the average. The smaller range for the 

coke burn-off emissions factors (as a percentage of the average) suggests that normalizing the 

emissions by coke burn-off accounts for more of the differences in the observed emissions than 

does throughput. Consequently, the average coke burn-off emissions factor would be preferred 

to the throughput-based emissions factor in this example. 

The highest individual run emission factor, 0.866 lb/1,000 lbs coke burn-off in this example, 

would be used, along with the maximum hourly coke burn-off rate during the year, to estimate 

the maximum hourly emission rate from this CCU. 
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HAP emissions estimates based on a site-specific PM emissions rate has been developed and requires 

additional explanation. The following subsections discuss additional guidance on providing a complete 

PM emissions estimate and on estimating metal HAP emissions from PM source test information. 

5.1.2.1 PM Emissions Inventory and Test Method Considerations 

PM emissions inventories have their own nomenclature and structure. To correctly report PM emissions, 

an understanding of the reporting nomenclature and the PM testing methods is needed. This subsection 

provides guidance and background information regarding PM emissions, with a focus on the PM test 

methods, particularly those methods commonly used when testing the CCU vent. 

EPA Methods 5, 5B, and 5F are the most commonly used test methods for measuring PM emissions from 

CCUs. A typical Method 5 sampling train consists of a sampling probe, a heated line and filter, and a 

series of impingers that are kept in an ice bath. Method 5, 5B, or 5F sampling measures PM that is 

contained in the sampling probe and filter, which is often referred to as the “front-half” or “filterable” PM 

catch. PM that condenses in the impinger section of the sampling train is often referred to as the “back 

half” catch or the “condensable” PM. 

One of the main differences between EPA Method 5, 5B, and 5F is that the sampling line and filter are 

maintained at 250°F for Method 5 compared to 325°F for Methods 5B and 5F. Although generally not 

used for the CCU, there are other EPA test methods for PM. EPA Method 17 is similar to Method 5, 

except that the filter in the Method 17 sampling probe is within the stack so that the “filterable” PM 

content is measured at the stack temperature. EPA Method 201 is similar to Method 17, except that there 

is also a cyclone or other sizing device to remove particles greater than 10 μm in diameter prior to the 

filter so that Method 201 determine PM10-FIL directly. EPA Method 201A, formerly EPA Other Test 

Method 27 (OTM 27), is similar to EPA Method 201 sampling at stack temperature, but uses a series of 

cylones to filter out, in succession, particles greater than 10 μm and 2.5 μm in diameter. The particle 

catch from the second cyclone can be used to determine the PM emissions that are less than 10 μm in 

diameter but greater than 2.5 μm in diameter. The “filterable” catch from OTM 27 is a direct measure of 

PM2.5-FIL. Therefore, EPA Method 201A provides a means to directly determine PM-FIL, PM10-FIL, and 

PM2.5-FIL. PM CEMS, if used, generally measure only the filterable PM (i.e., PM-FIL). 

Any of the Method 5, 17, or 201 variant methods describe only the procedures to determine the front-half 

or filterable PM catch. EPA Method 202, formerly EPA Other Test Method 28 (OTM 28), uses a dry 

condensing chamber followed liquid impingers and specifies the procedures to determine the mass of 

condensable PM (i.e., PM-CON). Although Method 202 generally references the use of Method 17 (or 

201 or 201A) sampling trains, it may also be used in conjunction with EPA Methods 5, 5B, or 5F. As the 

PM Emissions Inventory Nomenclature 

A complete PM emissions inventory includes the following components: 

 PM10-PRI: “Primary” PM emissions that are 10 μm in diameter or less. PM10-PRI = PM10-FIL + PM-CON. 

 PM10-FIL: Filterable (or front-half catch) portion of the PM emissions that are 10 μm in diameter or less. 

 PM-CON: Condensable PM (or back-half catch). All condensable PM is assumed to be less than 2.5 microns 

(μm) in diameter (PM2.5). 

 PM2.5-PRI: “Primary” PM emissions that are 2.5 μm in diameter or less. PM2.5-PRI = PM25-FIL + PM-CON. 

 PM2.5-FIL: Filterable (or front-half catch) portion of the PM emissions that are 2.5 μm in diameter or less. 

Although a complete PM emissions inventory includes PM emissions that are 10 μm in diameter or less, some 

measurement methods also collect PM particles that are greater than 10 μm in diameter. The following 

nomenclature is used to designate PM emissions that include PM greater than 10 μm in diameter: 

 PM-PRI: “Primary” PM emissions of any particle size. PM-PRI = PM-FIL + PM-CON. 

 PM-FIL: Filterable (or front-half catch) portion of the PM emissions of any particle size. 
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filter temperature in Method 5 is different from 

Methods 5B or 5F and also likely different from the 

filter temperature when using Method 17, the 

fraction of PM that is filterable versus condensable, 

which is a function of the sampling temperature, will 

also vary depending on the PM sampling method 

used. Because most of the data available for CCU 

were collected using EPA Methods 5B or 5F, the 

condensable PM default emissions factor is most 

suitable to filterable data collected using Methods 

5B or 5F, but may also be used in conjunction with 

Method 5 sampling data. If Method 202 is used, then 

the “back-half catch” can be considered PM-CON for the purposes of inventory reporting, regardless of 

the PM sampling method (i.e., sampling temperature) used. 

To summarize, PM CEMS and EPA Methods 5 (including 5B or 5F) and 17 provide a measure of PMFIL; EPA Method 201 provides a measure of PM-FIL and PM10-FIL; and EPA Method 201A provides a 

measure of PM-FIL, PM10-FIL, and PM2.5-FIL. EPA Method 202 provides a measure of PM-CON. One 

important caveat to this is that, in Method 5F, ammonia sulfate particulates are determined and subtracted 

from the total PM catch to determine the non-sulfate PM emissions. Although the non-sulfate PM value 

may be used for compliance purposes (for the Petroleum Refinery NSPS or for Refinery MACT II), 

emissions reported for the inventory should include the total filterable PM catch. That is, the total PM 

catch before subtracting the sulfate PM emissions should be used to determine PM-FIL for the purposes 

of reporting for the emissions inventory. The sulfate particulate PM should be considered to be 100% PM 

fine (i.e., PM2.5). Additional guidance on typical CCU particle size distributions is provided in the 

following subsection. 

5.1.2.2 PM Size Distribution Estimates for Catalytic Cracking Units 

AP-42 does not contain PM size distribution data for uncontrolled CCU PM emissions, but it does contain 

typical control device default control efficiencies for different types of PM emissions control devices. A 

limited number of particle size distribution studies were available in the docket to the Refinery MACT 2 

rule (40 CFR Part 63 Subpart UUU; Docket No. A-97-36, Item No. IV-D-19, Attachments 3, 6, and 9). 

From these data, the mass fraction of total filterable PM (front-half catch) that is less than 2.5 and 10 μm 

in diameter were determined and representative values are provided in Table 5-2. Table 5-2 also provides 

PM size distribution default values for controlled CCU. The default distribution factors for controlled 

CCU are based on the uncontrolled PM distributions and the control device default control efficiencies 

from AP-42. Because the projected size distribution of PM from different control devices was similar, one 

single set of distribution factors for controlled CCU are provided for controlled units. Control devices 

considered include tertiary cyclones, wet scrubbers, venturi scrubbers, ESP, and fabric filters. All PMCON is assumed to be less than 2.5 μm. The size distribution data guidance presented here is specific to 

FCCU. Facilities operating a TCCU should use site-specific size distribution data if available; otherwise, 

the default factors in Table 5-2 for a CCU with no post-regenerator PM control device should be used to 

project PM emissions by particle size. 

PM fine versus CCU fine 

Fine particles that escape from the CCU regenerator 

are often referred to as “fines” or “FCCU fines” by 

refinery personnel. In this Refinery Emissions 

Protocol document, fine particles that escape from 

the CCU regenerator are referred to as “CCU fines.” 

Please note that CCU fines are not equivalent to 

“PM fines,” which refers to particles that have a 

diameter of 2.5 μm or less. Generally, we use 

“PM2.5” to denote particles that have a diameter of 

2.5 μm or less. As noted in Table 5-2, only a fraction 

of the “CCU fines” are “PM fines.” 
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Table 5-2. Default Size Distribution for Filterable PM from CCU 

Source Description 

Fraction PM-FIL Less 

Than 2.5 μm 

Fraction PM-FIL Less 

Than 10 μm 

CCU, no post-regenerator PM control device 0.30 0.50 

CCU, with post-regenerator PM control device (tertiary 

cyclone, wet scrubber, ESP, or fabric filter) 

0.80 0.97 

Example 5-2: PM Emissions Inventory Calculations 

The following information is available for a 50,000 barrels/calendar day (bbl/cd) CCU 

controlled with an ESP. On average, the CCU burned 36,000 pounds of coke per hour and 

operated for 8,700 hours in the reporting year. During the most recent source test using EPA 

Method 5F, the CCU had non-sulfate PM emissions of 0.7 pound per 1,000 pounds of coke 

burn-off and PM emissions (including sulfates) of 0.9 pound per 1,000 pounds of coke burnoff. The “back-half” catch was also analyzed and was determined to be 0.45 pounds per 1,000 

pounds of coke burn-off. 

PM-FIL = 0.9 (lb/1,000 lb coke burn-off) × 36 (1,000 lb of coke burn-off per hour) × 8,700 

(operating hours per year) 

= 281,880 lb = 140.9 tons/yr 

PM-CON = 0.45 (lb/1,000 lb of coke burn-off) × 36 (1,000 lb of coke burn-off/hr) × 8,700 

(operating hours/yr) 

= 140,940 lb = 70.5 tons/yr 

PM-PRI = PM-FIL + PM-CON = 140.9 + 70.5 = 211.4 tons/yr 

For Method 5F, special consideration is made for the sulfate PM, because all of this PM is 

expected to be less than 2.5 μm. For Method 5 or 5B, PM10-FIL = (fraction < 10 μm from 

Table 5-2) × PM-FIL. For Method 5F, PM10-FIL = (fraction < 10 μm from Table 5-2) × 

PMnon-sulfate + PMsulfate. Similar consideration is needed for the PM2.5-FIL calculation. 

Because the CCU is controlled, the appropriate fractions from Table 5-2 are 0.97 for the 

PM10-FIL calculation and 0.80 for the PM2.5-FIL calculation. 

PMnon-sulfate = 0.7 (lb/1,000 lb coke burn-off) × 36 (1,000 lb coke burn/hr) × 8,700 (hr/yr) 

= 219,240 lb = 109.6 tons/yr 

PMsulfate = PM-FIL – PMnon-sulfates = 140.9 – 109.6 = 31.3 tons/yr 

PM10-FIL = fraction < 10 μm from Table 5-2] × PMnon-sulfate + PMsulfate 

= 0.97 × 109.6 + 31.3 = 137.6 tons/yr 

PM10-PRI = PM10-FIL + PM-CON = 137.6 + 70.5 = 208.1 tons/yr 

PM2.5-FIL = (fraction < 2.5 μm from Table 5-2) × PMnon-sulfate + PMsulfate 

= 0.8 × 109.6 + 31.3 = 119.0 tons/yr 

PM2.5-PRI = PM2.5-FIL + PM-CON = 119.0 +70.5 = 189.5 tons/yr 
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5.1.3 Methodology Rank 5A for CCU Metal HAP Emissions Estimates 

During CCU processing, metals deposit on the catalyst particles and slowly deactivate the catalyst. Also 

during processing, the catalyst particles may slowly break into finer particles, which can no longer be 

recovered by the CCU regenerator internal cyclones. To maintain the desired catalyst activity, a portion of 

the recirculating catalyst (i.e., E-cat) is regularly withdrawn from the process and new (fresh) catalyst is 

added. New catalyst particles often have irregularities (spurs) that break off during catalyst recirculation. 

Consequently, the CCU fines that escape from the CCU regenerator typically have a slightly higher 

proportion of fresh catalyst than does the E-cat. This is significant because fresh catalyst will have less 

metal deposits than a catalyst that has been recirculating for days or weeks. Available paired observations 

of E-cat and CCU fines data indicate that the metal HAP concentration on the CCU fines are consistently 

lower than on the E-cat, supporting the hypothesis that the CCU fines contain a higher fraction of fresh 

catalyst than does the E-cat. 

If metal HAP emissions tests are performed, then site-specific metal HAP emissions factors should be 

determined (using the methods provided in Section 5.1.2, Methodology Ranks 3 and 4 for Catalytic 

Cracking Units,) and used directly to assess metal HAP emissions rates as a Rank 4 method. However, 

few facilities are expected to have performed metal HAP speciation emissions tests for their CCU. On the 

other hand, nearly all facilities have their equilibrium catalyst (i.e., the catalyst within the CCU, 

commonly referred to as “E-cat”) tested regularly for certain metal contaminants to monitor catalyst 

activity and replacement needs. Some facilities also have their CCU fines tested occasionally for metal 

HAP concentrations. 

If a facility has a site-specific PM emissions factor, then either CCU fines or E-cat analysis can be used as 

a means to calculate a site-specific HAP emissions rate using the methodology described in this section. 

This Methodology Rank 5A for CCU metal HAP emissions estimates is expected to be more 

representative than a default emissions factor, but not as good as a directly measured HAP-specific 

emissions factor. This method involves using the site-specific (non-sulfate, if available) PM emissions 

rate, and estimating the concentration of metal HAP on the emitted PM based on the concentration of 

metal HAP on the CCU fines or E-cat using the procedures provided in this section. This method is not 

applicable for mercury (Hg) because it assumes the metals are associated with the catalyst particles and 

are not in the vapor phase. 

If metal HAP concentrations of CCU fines are available, then these data should be used (preferentially to 

E-cat data) to estimate the metal HAP concentration of the emitted PM. It is assumed that the emitted PM 

has the same metal HAP concentration as the CCU fines. If metal HAP concentrations for CCU fines are 

not available, then the metal HAP composition of the emitted PM can be estimated as 80% of the E-cat 

concentration. 

It is expected that CCU fine or E-cat concentration data will be available for nickel (Ni) and vanadium 

because these are the primary metals that poison CCU catalyst activity, but concentration data may be 

available for other metals as well. Table 5-3 lists metal HAP generally present in CCU fines. If the 

concentrations of these metal HAP are not determined for the CCU fines or E-cat, then they should be 

estimated using the measured Ni concentration and the concentration ratios for these other metal HAP as 

provided in Table 5-3. 

Equation 5-1 is a basic equation used to calculate annual metal HAP emissions based on the annual PM 

emissions rate and CCU fines metal HAP concentrations. 

1,000,000 mg/kg

i

i

C E = PM−FIL × (Eq. 5-1) 
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where: 

 Ei = Emissions rate of metal HAP “i” (tons/yr) 

 PM-FIL = Filterable PM emissions rate from site-specific PM emissions factor; if EPA Method 

5F is used, then use PMnon-sulfate rather than PM-FIL (ton/yr) 

 Ci = Concentration of metal HAP “i” on the CCU fines (milligrams per kilogram [mg/kg]) 

 = 0.8 × CE-cat,i, if only E-cat concentration are available 

 = CNickel × (factor from Table 5-3), if other metal HAP concentrations are not available 

Note that Ei = ENickel × (factor from Table 5-3) when other metal HAP concentration data are not 

available. If vanadium concentrations are available but nickel concentrations are not, the nickel 

concentration should be calculated by dividing the vanadium concentration by the default ratio for 

vanadium in Table 5-3, and the calculated nickel concentrations and the default ratios in Table 5-3 then 

used to project the concentrations of other metal HAPs. 

Table 5-3. Default Ratio of Metal HAP Composition of CCU Finesa

Metal HAP 

Ratio of Metal HAP 

to Nickel Concentration 

Antimony 0.065 

Arsenic 0.010 

Beryllium 0.003 

Cadmium 0.013 

Chromium (total)b 0.25b

Cobalt 0.052 

Lead 0.08 

Manganese 0.13 

Nickel 1.00 

Selenium 0.025c

Vanadiumd 1.32 

Zincd 0.74 

a

 Concentration ratios are based on average electrostatic precipitator dust 

analyses across six refineries. b

 Limited data are available to assess the amount for hexavalent chromium that 

is present, if any. If site specific data are not available, it is recommended that 

a default value of 10 percent of the total chromium emissions be used to 

estimate the hexavalent chromium emissions associated with the CCU. c

 Selenium was highly variable, being significant for some units and below the 

detection limit for several others. Consequently, this value is highly uncertain. d

 Vanadium and zinc are not HAPs, but are included here (and in Table 1-1) as 

other pollutants of interest. 
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Although total chromium emissions have been found above detectable concentrations in the CCU 

regenerator vent, very few tests have been performed to determine Cr+6 emissions. The few tests that have 

been performed have not found Cr+6 above detection limits, but the detection limits have been comparable 

to the detected total chromium emissions. Emissions of Cr+6 from coal-fired power plants indicated that 

Cr+6 emissions were 11 percent of the total chromium emissions (U.S. EPA, 1998c). Based on these 

limited data, it is recommended that, for the CCU vent, Cr+6 emissions be estimated as 10% of the total 

chromium emissions. Thus, in the example calculation provided, Cr+6 emissions would be estimated to be 

0.0026 tons/yr. 

Emissions of Hg should be estimated for the CCU; however, Hg emissions are not expected to be 

correlated with the PM emissions because very little, if any, of the Hg emissions are expected to be 

particulate bound. Mercury emissions are more likely correlated with the CCU throughput or coke burnoff rate. Thus, Hg emissions should be estimated independently of other HAP metals. If Hg emissions 

data are available based on source test data for the site, then the source test data can be used, as a 

Methodology Rank 4 for metal HAP emissions estimates, to develop a site-specific emissions factor. 

Otherwise, Hg emissions should be estimated using a default (Rank 5B) emissions factor rather than 

using this Rank 5A method. 

Example 5-3: Methodology Rank 5A for Metal HAP Emissions Estimates 

Following the previous example, PMnon-sulfate emissions were calculated to be 109.6 

tons/yr. If only Ni concentration for E-cat is available, what are the metal HAP emissions if 

the average Ni E-cat concentration is 1,200 mg/kg? 

The concentration of Ni on the emitted PM is calculated based on the E-cat concentration as 

follows: 

CNickel = 0.8 × 1,200 = 960 mg/kg 

The following equation should be used to calculate the emissions rate of Ni from the PM 

emissions rate on estimated Ni concentration: 

ENickel = 109.6 tons/yr × (960 mg/kg) ÷ (1,000,000 mg/kg) = 0.105 tons/yr 

The following equations should be used to estimate the emissions rate of other metal HAP 

from the emissions rate of Ni: 

EAntimony = 0.105 tons/yr × 0.065 = 0.0068 tons/yr 

EArsenic = 0.105 tons/yr × 0.010 = 0.00105 tons/yr 

EBeryllium = 0.105 tons/yr × 0.003 = 0.0003 tons/yr 

ECadmium = 0.105 tons/yr × 0.013 = 0.0014 tons/yr 

EChromium = 0.105 tons/yr × 0.25 = 0.026 tons/yr 

ECobalt = 0.105 tons/yr × 0.052 = 0.0055 tons/yr 

ELead = 0.105 tons/yr × 0.08 = 0.0084 tons/yr 

EManganese = 0.105 tons/yr × 0.13 = 0.014 tons/yr 

ESelenium = 0.105 tons/yr × 0.025 = 0.0026 tons/yr 

EVanadium = 0.105 tons/yr × 1.32 = 0.14 tons/yr 

EZinc = 0.105 tons/yr × 0.74 = 0.088 tons/yr 
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5.1.4 Methodology Rank 5B for Catalytic Cracking Units 

For most organic HAP (e.g., formaldehyde, benzene, benzo[a]pyrene, dioxin/furans) and other pollutants 

such as hydrogen cyanide and Hg, default emissions factors may be all that are available. When direct 

emissions monitoring or site-specific emissions factors are not available, then the default emissions 

factors presented in Table 5-4 should be used to calculate the emissions from the CCU regenerator vent. 

Note that all CCU are considered “controlled for organics” if they meet the 500 ppmv CO emissions limit. 

Table 5-4. Organic HAP Emissions Factors for CCU Catalyst Regenerator Vent 

CAS No. Compound 

Emissions Factor 

(lb/MMbbl)a Emissions Factor (lb/klb coke burn-off)b

Volatile Organics 

75-07-0 Acetaldehyde 20 0.0013 

67-64-1 Acetone 2.4 1.6E-4 

107-02-8 Acrolein 1.0 6.6E-5 

71-43-2 Benzene 18 1.1E-3 

74-83-9 Bromomethane 2.1 1.4E-4 

106-99-0 1,3-Butadiene 0.033 2.0E-6 

100-41-4 Ethylbenzene 0.24 1.6E-5 

50-00-0 Formaldehyde 260 0.016 

75-09-2 Methylene chloride 6.7 4.4E-4 

108-95-2 Phenol 8.7 5.7E-4 

108-88-3 Toluene 3.5 2.1E-4 

75-69-4 Trichlorofluoromethane 2.4 1.6E-4 

1330-20-7 Xylene 3.2 2.1E-4 

Semivolatile and Nonvolatile Organics(excluding dioxin/furans) 

83-32-9 Acenaphthene 0.0033 2.2E-7 

208-96-8 Acenaphthylene 0.13 7.8E-6 

120-12-7 Anthracene 0.10 6.7E-6 

56-55-3 Benzo(a)anthracene 0.00052 3.8E-8 

50-32-8 Benzo(a)pyrene 0.011 7.1E-7 

205-99-2 Benzo(b)fluoranthene 0.0035 2.4E-7 

192-97-2 Benzo(e)pyrene 0.00045 3.3E-8 

191-24-2 Benzo(g,h,i)perylene 0.0046 3.1E-7 

207-08-9 Benzo(k)fluoranthene 0.0026 1.8E-7 

218-01-9 Chrysene 0.0033 2.3E-7 

53-70-3 Dibenz(a,h)anthracene 0.0042 2.8E-7 

206-44-0 Fluoranthene 0.093 6.1E-6 

86-73-7 Fluorene 0.037 2.4E-6 

193-39-5 Indeno(1,2,3-cd)pyrene 0.0044 3.0E-7 

91-57-6 2-Methylnaphthalene 0.026 1.8E-6 

91-20-3 Naphthalene 1.0 7.0E-5 

85-01-8 Phenanthrene 0.24 1.6E-5 

129-00-0 Pyrene 0.0031 2.2E-7 

(continued) 
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Table 5-4. Organic HAP Emissions Factors for CCU Catalyst 

Regenerator Vent (continued) 

CAS No. Compound 

Emissions Factor 

(lb/MMbbl)a Emissions Factor (lb/klb coke burn-off)b

Dioxins/Furans 

57117-31-4 Pentachlorodibenzofurans 5.5E-07 3.2E-11 

57117-44-9 Hexachlorodibenzofuran 1.1E-06 6.3E-11 

35822-46-9 Heptachlorodibenzo-p-dioxin 9.4E-07 5.6E-11 

Inorganics 

7664-41-7 Ammonia 13,000 0.57 

75-15-0 Carbon disulfide 0.56 3.7E-5 

7647-01-0 Hydrogen chloride 1,800 0.11 

74-90-8 Hydrogen cyanide 770 0.049 

7439-97-6 Mercury 1.1 6.0E-5 

a

 Emissions factors for CCU controlled for organics in pounds per million barrels of CCU feed. 

b

 Emissions factors for CCU controlled for organics in pounds per thousand pounds of coke burn-off.

The emission factors presented in Table 5-4 are based on the emission data collected to support the 

Refinery MACT 2 rule. While there appear to be slight differences in how outlier and non-detect values 

were handled, the emission factors in Table 5-4 agree well with the average emission factors developed 

by Bertrand and Siegell (2002). 

Based on the lack of data for PAH and furan emissions, the emissions estimates for these compounds 

have high uncertainties, likely an order-of-magnitude either high or low. The California Air Resources 

Board (CARB), with EPA’s support, conducted an emissions source test at a complete combustion FCCU 

(without a post-combustion device). The only dioxin isomer detected in all runs was octachloro-dibenzop-dioxin (OCDD); octachloro-dibenzo-furan (OCDF) and heptachloro-dibenzo-p-dioxin (hepta-CDD) 

were detected in one run. All dioxin/furan quantities that were detected were detected at levels below the 

method quantitation limit for the analysis. All polychlorinated biphenyls (PCBs) isomers were below 

detection limits. This additional source test was not included in the development of the Petroleum 

Refinery MACT II emissions factors, but it confirms low emissions of dioxins/furans and PCBs from the 

CCU catalyst regenerator vent. 

5.2 Fluid Coking Units 

Coking units use heat to thermally crack heavy hydrocarbon streams to form lighter, more useful 

distillates such as heating oils or gasoline. There are three basic types of coking units: traditional fluid 

coking units, flexicoking units, and delayed coking units. Traditional fluid coking units are one of the 

largest vent emissions sources at a refinery, being comparable to emissions from the CCU regenerator. 

However, there are only a handful of traditional fluid coking units currently in operation in the United 

States. Flexicoking units, which are also rare, do not have a direct atmospheric vent. Instead, these units 

produce a low heating value syngas that can be subsequently used as fuel in process heaters or boilers. 

Emissions from the combustion of flexicoking syngas should be determined using the methods described 

in Section 4, Stationary Combustion Sources. Nearly all new coking units being built at refineries are 

delayed coking units, which are discussed further in Section 5.3. 

Fluid coking units have several similarities to a CCU. The coking unit contains a burner section and a 

reactor section. In the burner section, heat for the coking reaction is supplied by burning a portion of the 

coke that is produced. In the reactor, fine coke particles are produced as a result of the thermal cracking 
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process. Prior to exiting the coking unit, coke particles entrained with the flue gases are removed by 

internal cyclone separators and recovered as a product, with a portion of the produced coke recycled to 

the burner section. The coke burner is operated with limited air—enough to combust the diverted coke (to 

provide heat for the coking reaction)—but limited enough to prevent O2 from getting into the reactor 

section. The exhaust gas from the coking unit burner has high levels of CO, which is typically combusted 

in a CO boiler to recover the latent heat of the CO. The CO boiler also acts to combust any organics 

entrained in the flue gas. The gas may then be further processed to remove PM or SO2 in the flue gas. The 

fluid coking unit vent releases a wide variety of pollutants, including PM, SO2, NOx, CO, VOC, metal 

HAP, organic HAP, and ammonia. 

Special considerations should be taken to estimate the amount of total sulfur compounds present in fuel 

gas generated from the fluid coking unit. Coking units have been found to produce appreciable quantities 

of methyl mercaptans and other reduced sulfur compounds that are not as efficiently removed from sour 

gas as is H2S. Consequently, SO2 emissions from fuel gas combustion devices receiving fuel gas 

generated from a fluid coking unit should account for this additional sulfur that is not measured by H2S 

monitors (see Section 4, Stationary Combustion Sources, for further details). 

Note also that fluid coking units, in particular, may have significant fugitive PM emissions from the 

handling of the produced coke. Methodologies for these fugitive PM emissions are described in Section 

10, Fugitive Dust Sources. 

5.2.1 Methodology Ranks 1 and 2 for Fluid Coking Units 

For SO2, NOx, CO, and CO2, it is anticipated that most units will have CEMS for measuring the 

composition of the exhaust gas. Gas flow rate may be directly monitored, but in many cases, the exhaust 

flow rate will be calculated based on air blast rates and composition monitors (similar to F factors). 

5.2.2 Methodology Ranks 3 and 4 for Fluid Coking Units 

Source tests should be available for PM (and perhaps SO2 and NOx, if not continuously monitored) so that 

site-specific emissions factors should be available. It is anticipated that the pollutant emissions will 

primarily be a function of the coke burn rates; however, limited data are available to assess this 

hypothesis. 

5.2.3 Methodology Rank 5 for Fluid Coking Units 

We do not have data to provide default emissions factors for fluid coking units. 

5.3 Delayed Coking Units 

Coking units use heat to thermally crack heavy hydrocarbon streams to form lighter, more useful 

distillates such as heating oils or gasoline. Most of the coking units in operation within the United States 

are delayed coking units. Unlike most other refinery operations that are continuous, delayed coking units 

are operated in a semi-batch system. Most delayed coking units consist of a large process heater, typically 

two coking drums, a single product distillation column, and coke cutting equipment. The process heater 

heats the heavy feed oil to near cracking temperatures, and then the oil is fed to one of the coking drums. 

As the cracking reactions occur, coke is produced in the drum and begins to fill the drum with sponge-like 

solid coke material. Once filled, the feed is diverted to the second coke drum. The full coke drum is 

cooled by slowly adding water to the vessel, which quickly turns to steam, and the steam helps to cool 

and purge organics in the coke matrix. After the coke drum is sufficiently cooled, the drum is opened and 

the coke is removed from the vessel using high-pressure water. Once the coke is cut out of the drum, the 

drum is closed, and prepared to go back online. A single coke drum is typically on-line receiving oil for 

14 to 18 hours and then off-line for cooling and decoking for 14 to 18 hours, so a complete cycle time is 

approximately 28 to 36 hours. 
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During the reaction process, the delayed coking unit is a closed system. When the coke drum is taken offline, the initial steaming process gas is also recovered through the unit’s product distillation column. As 

the steaming cycle continues, the gas is sent to a blowdown system to recover the liquids. The gas is 

typically sent to a flare or other control device but may be released to the atmosphere. Near the end of the 

steaming process, a vent is opened to allow the remaining steam and vapors to be released into the 

atmosphere prior to opening the drum. Emissions from delayed coking units are primarily CH4 and 

ethane, but include a variety of volatile and semi-volatile organics. 

Although this section primarily addresses the vent emissions from the delayed coking unit, fugitive 

emissions are also released from the delayed coking unit when the coke drum is opened and the coke is 

cut from the drum. During this cutting process, hydrocarbons that were retained in the internal coke pores 

will be released into the atmosphere. At this time, however, no methods are available for estimating the 

direct organic releases during coke cutting. PM emissions from the coke cutting operations and 

subsequent coke storage and handling facilities should be estimated using the methodologies described in 

Section 10, Fugitive Dust Sources. The cutting water will absorb some hydrocarbons, so this water will 

also become a source of organic emissions; therefore, organic emissions from impoundments, ponds, or 

open tanks used to store the cutting liquids should be estimated using the methodologies described in 

Section 7.2.5, Equalization Tanks. 

As with fluid coking units, special considerations should be taken to estimate the amount of total sulfur 

compounds that are present in fuel gas generated from delayed coking units. Coking units have been 

found to produce appreciable quantities of methyl mercaptans and other reduced sulfur compounds that 

are not efficiently removed from the sour gas as H2S. Consequently, SO2 emissions from fuel gas 

combustion devices receiving fuel gas generated from a delayed coking unit should account for this 

additional sulfur that is not measured by H2S monitors (for more detail, see Section 4, Stationary 

Combustion Sources). 

5.3.1 Methodology Ranks 1 and 2 for Delayed Coking Units 

Delayed coking units vent periodically and only for relatively short periods of time during 

depressurization of the unit after the coking cycle. As such, delayed coking units are not expected to use 

CEMS. If CEMS are used, Methodology Rank 1 for process vents could be used. The gas flow rate 

cannot be estimated using F factors, so Methodology Rank 2 for process vents is not applicable to the 

delayed coking unit vent. 

5.3.2 Methodology Ranks 3 and 4 for Delayed Coking Units 

A limited number of source tests have recently been performed on delayed coking unit vents. For 

facilities that have performed source tests, site-specific emissions factors can be developed and used. It is 

anticipated that the pollutant emissions will be a function of coking vessel void volume and initial vent 

pressure; however, for a particular delayed coking unit, these variables are fairly constant and a per cycle 

emissions rate from the source test can be used. 

5.3.3 Methodology Rank 5 for Delayed Coking Units 

Source test data are available for five delayed coking units (SCAQMD, 2004a, 2004b, 2004c, and 2004d; 

URS Corporation, 2008). From these data, average concentrations and emissions factors were developed 

(see Table 5-5). While the emissions are expected to be higher for units that start to depressurize at higher 

coke drum pressures, the emissions were also dependent on the time steaming occurred prior to 

depressurization and the temperature of the drum (how much additional steam was generated after the 

steam vent was opened. Due to the complexities of the delayed coking unit steam vent and the limited test 

data available, correlations to account for different process variables (venting pressure, drum temperature 

and steaming time prior to venting) are not currently available, and the default emissions factors in 

Table 5-5 should be used when site-specific measurement or test data are not available. 
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Table 5-5. Average Vent Concentrations and Emissions Factors for Delayed Coking Unit Vents 

CAS No. Compound 

Vent Concentration 

(ppmv, wet basis) 

Emissions Factor 

(lb/cycle)a

106-99-0 Methane 7,600 200 

74-84-0 Ethane 1,060 42 

VOC Nonmethane/nonethane VOC 820 b 57 

71-43-2 Benzene 9.4 0.1 

108-88-3 Toluene 24 5.6 

100-41-4 Ethylbenzene 1.7 0.03 

1330-20-7 Xylene 15 0.24 

108-95-2 Phenol 0.12 

1319-77-3 Cresols (total) 0.23 

105-67-9 2,4-Dimethylphenol 0.086 

62-53-3 Aniline 0.057 

POM Total all POM 6.4 

83-32-9 Acenaphthene 0.070 

208-96-8 Acenaphthylene 0.004 

120-12-7 Anthracene 0.15 

56-55-3 Benzo(a)anthracene 0.031 

50-32-8 Benzo(a)pyrene 0.027 

205-99-2 Benzo(b)fluoranthene 0.007 

191-24-2 Benzo(g,h,i)perylene 0.014 

207-08-9 Benzo(k)fluoranthene 0.005 

218-01-9 Chrysene 0.032 

53-70-3 Dibenz(a,h)anthracene 0.010 

206-44-0 Fluoranthene 0.024 

86-73-7 Fluorene 0.18 

193-39-5 Indeno(1,2,3-cd)pyrene 0.007 

91-20-3 Naphthalene 1.7 

85-01-8 Phenanthrene 0.46 

129-00-0 Pyrene 0.080 

91-57-6 2-Methylnaphthalene 2.9 

a

 Emissions are in pounds per emissions event or per cycle considering a single coke drum. 

b

 Concentration of VOC reported as propane. 

5.4 Catalytic Reforming Units 

The CRU is a series of catalytic reactors that turn naphtha into high-octane gasoline. There are no direct 

atmospheric vents from the naphtha-reforming process, but the catalyst activity slowly diminishes with 

time and the catalyst must be regenerated. There are three basic types of CRU catalyst regeneration 

operations: continuous, cyclic, and semi-regenerative. Continuous CRU catalyst regenerators operate 

continuously with a small slip stream of catalyst being re-circulated between the CRU and the 

regenerator. In cyclic CRU, there is essentially an extra CRU reactor. When regeneration is needed, one 

reactor is cycled offline and regenerated. The regeneration of the offline reactor is a batch process. When 

complete, the reactor is returned to service, and the next reactor is cycled offline and regenerated. This 

process continues until all reactors are regenerated. In a cyclic CRU, regeneration may occur for 1,000 to 
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4,000 hours per year. The semi-regenerative CRU operates without regeneration for 8 to 18 months, then 

the entire unit is brought offline, and the entire unit is regenerated. The overall regeneration cycle 

typically takes 1 to 2 weeks. 

During regeneration, there are several potential atmospheric vents. Although the location of the emission 

points might vary depending on whether catalyst regeneration is continuous, cyclic, or semi-regenerative, 

there are three times or locations during the regeneration process that emissions can occur regardless of 

the regenerator type. For continuous regeneration, venting occurs from three distinct vents as follows: 

(1) the initial depressurization and purge vent; (2) the coke burn pressure control vent; and (3) the final 

catalyst purge vent. For cyclic and semi-regenerative units, the initial depressurization and purge vent is 

often a distinct release point, but the coke burn and final catalyst purge emissions are commonly released 

at different times during the regeneration cycle from a single atmospheric vent. 

The initial depressurization and purge cycle removes the hydrocarbons from the catalyst prior to CRU 

catalyst regeneration. The vent gases from this initial purge may have high levels of organic HAP such as 

benzene, toluene, xylene, and hexane. The gases generated from the initial depressurization and purge 

cycles are typically vented to the refinery fuel gas system or directly to a combustion device (e.g., flare or 

process heater). The coke burn cycle is typically the largest (in terms of gas volume) emissions source of 

the overall catalyst regeneration cycle. The primary HAP contained in the CRU coke burn vent are 

hydrogen chloride (HCl) and chlorine (Cl2), which are produced when the water formed during 

combustion leaches chloride atoms from the CRU catalyst. The final purge and reduction cycle removes 

O2 and any remaining chlorination agent from the system and reduces the catalyst prior to returning the 

CRU catalyst to the reforming process or bringing the unit back online. The vent gases from this final 

purge may have low levels of the chlorinating agent (usually an organic HAP such as trichloroethene or 

perchloroethene) and residual HCl or Cl2 remaining in the system. The final purge gases are typically 

vented into the atmosphere or to the refinery fuel gas system depending on the O2 content of the purge 

gases (safety considerations restrict the venting of O2-containing gases to the refinery fuel gas system). 

5.4.1 Emissions Estimation Methodology for Catalytic Reforming Units 

Few data are available to characterize the emissions from the CRU catalyst regeneration vent because 

venting is infrequent, the vent flow rates are slow and usually variable, and the vents have small 

diameters. All of these factors make traditional source testing difficult. Most of the available data are for 

HCl and Cl2 emissions from uncontrolled coke burn vents (20 data points are available for HCl emissions; 

10 data points are available for Cl2). A few data points were available for a limited number of organic 

chemicals. These data are compiled in the Background Information Document (BID) for the proposed 

Petroleum Refinery MACT II rule (U.S. EPA, 1998b). During the Petroleum Refinery MACT II project, 

CARB, with funding assistance from EPA, conducted a source test of a continuous CRU catalyst 

regenerator coke-burn vent for dioxins/furans, PCBs, and PAHs. The results from this source test, which 

were not available at the time for inclusion into the Petroleum Refinery MACT II BID, were used to 

develop emissions factors for these compounds. The emissions factors used for the uncontrolled coke 

burn emissions are presented in Table 5-6. These emissions factors are normalized by the CRU process 

throughput and are assumed to apply equally for all types of CRU regenerators. 

The most prevalent control device used in association with the coke-burn vent is a wet scrubber. The 

dioxin/furan emissions source tests and the volatile organics were performed on a system controlled by a 

wet scrubber. Because of the limited solubilities of these chemicals and the scrubbing medium 

recirculation rate used for wet scrubbers on this vent stream, the scrubber is assumed to have limited 

effectiveness at reducing the emissions of these chemicals. Therefore, the same emissions factor is 

recommended for these chemicals for both controlled and uncontrolled CRU. Wet scrubbers are used to 

reduce the emissions of HCl and Cl2. The wet scrubbers used for these vents were characterized into two 

classes: single-stage scrubbers and multiple-stage scrubbers. Single-stage scrubbers are estimated to 
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reduce HCl and Cl2 emissions by 92%, and the multiple-stage scrubbers are estimated to reduce HCl and 

Cl2 emissions by 97%. 

As most emissions from the purge cycles are vented to the refinery fuel gas system or a flare, emissions 

from this source were not covered separately in this section; these emissions are presumably included in 

the refinery fuel gas combustion sources (process heaters and boilers) or flares emissions estimates. No 

data are available to characterize the small portion of venting that occurs directly into the atmosphere 

from these purge cycles, but these emissions should be characterized and reported in the inventory. 

Table 5-6. Emissions Factors for CRU Catalyst Regeneration Vent 

CAS No. Chemical Name 

Emissions Factor 

(lb/1,000 bbl)a

1746-01-6 Dioxin toxic equivalents (TEQ)b 5.7E-09 

1336-36-3 Total polychlorinated biphenylsc 2.6E-06 

91-20-3 Naphthalene 3.5E-05 

91-57-6 2-Methylnaphthalene 1.3E-06 

208-96-8 Acenaphthylene 3.0E-08 

83-32-9 Acenaphthene 4.3E-08 

86-73-7 Fluorene 2.0E-07 

85-01-8 Phenanthrene 6.1E-07 

120-12-7 Anthracene 9.1E-08 

206-44-0 Fluoranthene 1.0E-07 

129-00-0 Pyrene 1.5E-08 

56-55-3 Benzo(a)anthracene 9.0E-10 

218-01-9 Chrysene 2.9E-09 

205-99-2 Benzo(b)fluoranthene 1.5E-09 

207-08-9 Benzo(k)fluoranthene 7.5E-10 

192-97-2 Benzo(e)pyrene 2.9E-09 

193-39-5 Indeno(1,2,3-c,d)pyrene 1.7E-09 

53-70-3 Dibenzo(a,h)anthracene 7.8E-10 

191-24-2 Benzo(g,h,i)perylene 4.0E-09 

71-43-2 Benzene 0.004 

108-88-3 Toluene 0.0096 

1330-20-7 Xylene 0.007 

7647-01-0 Hydrogen chloride 4.2d

7782-50-5 Chlorine 0.23d

a

 Emissions factor in pounds pollutant emitted per 1,000 barrels of catalytic reforming unit process 

capacity. b

 Dioxin TEQ = toxic equivalents to 2,3,7,8-tetrachloro-dibenzo-p-dioxin used for risk analysis; specific 

dioxin/furan isomer emissions data are available. c

 Sum total of all chlorinated biphenyl emissions factors; data were available for each class of 

chlorinated biphenyls (e.g., mono-, di-, tri-..., decachlorobiphenyl). d

 Emissions factor for uncontrolled coke burn vent; controlled emissions should be estimated based on 

the efficiency of the control device for these pollutants. Single-stage scrubbers (including direct caustic 

injection) are estimated to reduce HCl and Cl2 emissions by 92%, and the multiple-stage scrubbers are 

estimated to reduce HCl and Cl2 emissions by 97% 
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5.5 Sulfur Recovery Plants 

All crude oils contain some sulfur compound impurities. Sulfur compounds in crude oil are converted to 

H2S in the cracking and hydrotreating processes of the refinery. The H2S in the generated gas streams is 

removed from the process vapors using amine scrubbers. The amine scrubbing solution is subsequently 

heated to release the H2S to form an H2S rich “acid gas” that is treated in the sulfur recovery plant to yield 

high-purity sulfur that is then sold as product. Most sulfur recovery plants use the Claus reaction and are 

commonly referred to as Claus units or Claus sulfur recovery plants. There are a couple of other types of 

sulfur recovery plants at smaller refineries, but all larger sulfur recovery plants employ Claus units. The 

exhaust gas from the sulfur recovery unit (SRU) is commonly referred to as “tail gas.” The sulfur 

recovery plant consists of one or more SRU operated in parallel and may also contain one or more 

catalytic tail gas treatment units and/or a thermal oxidizer to combust the tail gas. 

The primary HAP components of the final sulfur plant vent are carbonyl sulfide (COS) and carbon 

disulfide (CS2). These HAP components are by-products of the SRU and tail gas treatment unit (TGTU) 

reactions; COS may also be a product of incomplete combustion from a thermal oxidizer. Unreacted H2S 

may also be released during the process. Sulfur recovery plant vents are commonly controlled by a 

thermal oxider to oxidize unreacted H2S or H2S in sweep gas from the sulfur pits to SO2. Some sulfur 

recovery plants use reducing controls and thus emit H2S rather than SO2. The sulfur plant sour gas feed 

may also contain small amounts of light organics. Therefore, it is important to account for the 

hydrocarbons in the sulfur recovery plant feed when estimating emissions from the sulfur recovery plant, 

particularly from Lo-Cat® or other sulfur recovery plants that may have atmospheric vents without 

thermal destruction. 

When the sulfur recovery plant is in operation, the sulfur plant vent flow rate is fairly small so that the 

SO2 emissions from the sulfur recovery plant are also relatively small. If the sulfur recovery plant must be 

taken offline due to an upset or malfunction, the sour gas may be temporarily directed to a backup sulfur 

recovery unit or directed to a flare or the thermal oxidizer. If the sour gas in these cases is sent to a flare 

or thermal oxidizer, the SO2 emissions can be very large. As such, it is critical to include accurate 

accounting of SO2 emissions during startup, shutdown, or malfunction (SSM) events associated with the 

sulfur recovery plant. 

5.5.1 Methodology Ranks 1 and 2 for Sulfur Recovery Plants 

It is anticipated that most sulfur recovery plants, particularly Claus sulfur recovery plants, will have 

continuous SO2 concentration monitors. When continuous flow monitors are also in place, mass 

emissions rates can be calculated using the CEMS method previously described in Section 4, Stationary 

Combustion Sources. Unlike combustion sources, however, there is not an F factor method to project the 

vent flow rate. If the flow rate and H2S concentration of the feed to the sulfur recovery plant, the air or 

oxygen feed rates to the sulfur plant burner (used to convert one-third of the H2S to SO2), and the quantity 

of sulfur recovered are known, then calculations to determine/quantify emissions can be made, but the 

calculations are not trivial. As such, there is not a simple Rank 2 method that can be provided for sulfur 

recovery plants. Non-Claus sulfur recovery plants may monitor H2S or reduced sulfur compound 

concentrations instead of SO2. Again, H2S emissions estimates should be provided for sulfur recovery 

plants. 

5.5.2 Methodology Ranks 3 and 4 for Sulfur Recovery Plants 

Emissions estimates can be made from inlet flow measurements and assumed recovery efficiencies. For 

most Claus units, especially those with tail gas treatment/recovery units, a mass balance approach for 

sulfur is expected to yield emissions estimates with high uncertainties (e.g., when two large numbers are 

subtracted so that the difference is only a few percentages of the original values, the uncertainties in the 

original values may be as large as the difference). A three-stage Claus unit is expected to have sulfur 
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recovery efficiencies of 95% to 97%. Combining a three-stage Claus unit with a tail gas treatment unit, 

sulfur recovery efficiencies are expected to be 99.7% to 99.9%. With these types of recovery efficiencies, 

the mass balance approach (i.e., calculating SO2 or other sulfur compound emissions from the difference 

of the sulfur feed rate to the SRU and the sulfur produced) will have significant uncertainty. 

Consequently, measurement of the mass feed rate of sulfur to the sulfur recovery plant and an assumed 

sulfur recovery efficiency (based on the number of Claus reactors in series and the presence or absence of 

a tail gas treatment unit) are likely to be more accurate than using a mass balance approach when 

calculating sulfur compound emissions from the sulfur recovery plant. A similar approach can be used to 

calculate CO2 emissions from the sulfur recovery plant, particularly in systems controlled with a flare or 

thermal oxidizer. Because nearly all of the CO2 or hydrocarbons introduced to the sulfur recovery plant 

will exit as CO2, measuring inlet C content and flow rate of gases to the sulfur recovery plant can be used 

to accurately estimate CO2 emissions. 

Given the high uncertainty expected in engineering/mass-balance calculations for sulfur recovery plants, 

site-specific emissions factors may be as or more useful than using an engineering/mass-balance approach 

for calculating emissions from sulfur recovery plants, particularly sulfur compound emissions. Sitespecific emissions factors are also recommended for reductive tail gas treatment units not followed by an 

incinerator and for non-Claus sulfur recovery plants. Evaluation of light hydrocarbons should be 

addressed in these systems. For example, Lo-Cat® systems use an oxidation tank in which H2S is 

chemically oxidize to SO2. Any light hydrocarbons entrained in the sour gas are expected to be released in 

the vent from the oxidation tank. The emissions from this oxidation tank should be characterized and 

reported for the sulfur recovery plant. 

5.5.3 Methodology Rank 5 for Sulfur Recovery Plants 

The Petroleum Refinery MACT II BID (U.S. EPA, 1998b) presents a range of total sulfur HAP 

compounds emissions factors for SRU controlled by an incinerator. Based on the data presented and 

additional concentration data submitted by the National Petrochemical and Refiners Association, it was 

assumed that 75% of the sulfur HAP emitted was COS and 25% was CS2. The controlled emissions 

factors are based on summary data reported for five SRUs. Emissions of uncontrolled sulfur HAP were 

estimated assuming a control efficiency of 98% (so that uncontrolled emissions are 50 times higher than 

controlled emissions). The resulting emissions factors are presented in Table 5-7. 

Table 5-7. Emissions Factors for Sulfur Recovery Plants 

CAS No. Compound Name 

Controlled SRU Emissions 

Factor (lb/lton)a Uncontrolled SRU Emissions Factor (lb/lton)a

43-58-1 Carbonyl sulfide 0.12 5.85b

75-15-0 Carbon disulfide 0.040 2.00b

Note: lb/lton = pounds per long ton a

 Emissions factor in pounds of HAP per long-ton of sulfur produced. 

b

 Values estimated as 50 times the controlled SRU emissions factor. 

5.6 Other Miscellaneous Process Vents 

There are many other process vents at a refinery; however, there are limited data for these vents, so 

default emissions factors are not available. For these process vents, this section provides a brief 

description of the process, the vent source, and the primary pollutants associated with the process vent. 

For all of these sources, the general hierarchy of methods as presented in Table 5-1 in the introduction to 

this chapter is applicable. For atmospheric vents associated with continuous monitoring systems, the flow 

rate and composition of the purged gases should be well characterized and emission estimates can be 

developed using Methodology Rank 1 for process vents. For other process vents, measurement data may 

not be available. Engineering or model estimates can be used to estimate the uncontrolled emissions. If 
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the emissions are subsequently controlled, the actual emissions can be estimated based on the efficiency 

of the control device. The purpose of this section is to provide default emission factors for Methodology 

Rank 5 for these particular process vents. 

5.6.1 Hydrogen Plant Vents 

Steam CH4 reforming is the primary means by which H2 is produced at a petroleum refinery. Refinery 

fuel gas is typically used as the feedstock to the H2 plant. The feedstock is combined with steam in a 

reactor at high temperatures (750°C to 800°C) to produce a mixture of H2 and CO. A water–gas shift 

reaction occurs in a series of catalytic reactors to convert the CO and steam to CO2 and H2. Finally, the 

CO2 is removed from the H2 product using either a liquid absorption system or pressure swing absorption. 

The H2 plant vent contains relatively high levels of methanol and may also contain formaldehyde and 

other light hydrocarbons; however, no default emission factors are available at this time for the hydrogen 

plant vent. 

5.6.2 Asphalt Plant Vents 

Asphalt blowing is used for polymerizing and stabilizing asphalt to improve its weathering characteristics. 

Air-blown asphalts are used in the production of asphalt roofing products and certain road asphalts. Air 

blowing of asphalt may be conducted at petroleum refineries, asphalt processing plants, and asphalt 

roofing plants. Asphalt blowing involves the oxidation of asphalt flux by bubbling air through liquid 

asphalt flux at 260°C (500°F) for 1 hour to 10 hours. The amount of time depends on the desired 

characteristics of the product, such as the softening point and the penetration rate. Shorter periods are 

typically used for road asphalt; longer periods are used for roofing asphalt. Asphalt blowing results in an 

exothermic reaction that requires cooling. The emissions from a blowing still are primarily organic 

particulate with a fairly high concentration of gaseous hydrocarbon and polycyclic organic matter. The 

blowing still gas is commonly controlled with a wet scrubber to remove sour gas, entrained oil, 

particulates, and condensable organics and/or a thermal oxidizer to combust the hydrocarbons and sour 

gas to CO2 and SO2. 

Overall PM and TOC emissions factors for asphalt blowing are provided in Section 11.2 of AP-42 (U.S. 

EPA, 1995a); these emission factors are also presented here in Table 5-8. 

Table 5-8. Emission Factors for Asphalt Blowing (U.S. EPA, 1995a) 

Operation 

Filterable PMa TOCb

Emission Factor (Data Quality Rating) 

(lb/ton asphalt processed) 

Uncontrolled 

Saturant asphalt c 6.6 (E) 1.3 (E) 

Coating asphalt d 24 (E) 3.4 (E) 

Controlled 

Saturant asphalt c 0.27 (D) 0.0043 (D) 

Coating asphalt d 0.81 (D) 0.017 (D) 

a

 Filterable (front-half) particulate matter catch using EPA Method 5A sampling at 108°F. b

 Total organic compounds measured using EPA Method 25A. 

c

 Saturant blow of 1.5 hours. 

d

 Coating blow of 4.5 hours. 
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5-20 

Tumbore (1998) provided an additional summary and evaluation of emissions from controlled asphalt 

blowing. Some key findings from this review were: 

 The AP-42 emission factors ignore emissions of SO2, which are usually the largest emissions 

from the process. For gas fired control systems, H2S resulting from the asphalt blowing reaction 

accounted for 70 to 80 % of the SO2 emissions, with the remainder attributable to entrained or 

condensed oil. 

 The AP-42 emission factors ignore emissions of HCl, which are important when ferric chloride is 

used as a catalyst in the process. 

The Emission Inventory Guidebook 2006 (EMEP/CORINAIR, 2006) provides the following speciation 

profile for organic emissions from asphalt blowing (see Table 5-9). Although not specified, it is assumed 

that this speciation profile in Table 5-9 represents uncontrolled asphalt blowing emissions. 

Table 5-9. Asphalt Blowing – Nonmethane Volatile Organic Compounds Speciationa

Compound % Weight 

Ethane 6.0 

Propane 18.8 

Butanes 30.5 

Pentanes 17.2 

Hexanes 8.4 

Heptanes 9.8 

Octanes 7.4 

Cycloparaffins 1.9 

Benzene 0.1 

a As reported by EMEP/CORINAIR, 2006. 

In addition, API and the Western States Petroleum Association (WSPA) conducted emissions source tests 

of petroleum refining sources and have compiled emissions factors for controlled asphalt blowing 

(Hansell and England, 1998). The average emissions factors are presented in Table 5-10. These factors 

are recommended for estimating speciated emissions from controlled asphalt blowing units. 

Table 5-10. Summary of Emissions Factors for Controlled Asphalt Blowing 

CAS Number Substance 

Mean Emissions Factora

With Blow 

Cycle and 

Thermal 

Oxidizer 

(lb/MMcf)b

With Blow 

Cycle and 

Thermal 

Oxidizer 

(lb/MMBtu)b

Without Blow 

Cycle and with 

Thermal 

Oxidizer 

(lb/MMcf)b

Without Blow 

Cycle and with 

Thermal 

Oxidizer 

(lb/MMBtu)b

75-07-0 Acetaldehyde 1.8E-03 1.67E-06 4.3E-03 4.1E-06 

7440-28-2 Arsenic 1.3E-02 1.2E-05 1.2E-02 1.1E-05 

71-43-2 Benzene 3.2E-01 3.0E-04 2.8E-01 2.6E-04 

7440-41-7 Beryllium 2.6E-03 2.5E-06 2.3E-03 2.2E-06 

7440-43-9 Cadmium 5.3E-03 4.9E-06 4.7E-03 4.4E-06 

(continued) 
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Table 5-10. Summary of Emissions Factors for Controlled Asphalt Blowing (continued) 

CAS Number Substance 

Mean Emissions Factora

With Blow 

Cycle and 

Thermal 

Oxidizer 

(lb/MMcf)b

With Blow 

Cycle and 

Thermal 

Oxidizer 

(lb/MMBtu)b

Without Blow 

Cycle and with 

Thermal 

Oxidizer 

(lb/MMcf)b

Without Blow 

Cycle and with 

Thermal 

Oxidizer 

(lb/MMBtu)b

18540-29-9 Chromium 

(hexavalent) 

3.2E-03 3.0E-06 3.3E-03 3.1E-06 

7440-47-3 Chromium (total) 4.2E-02 3.9E-05 1.4E-02 1.3E-05 

7440-50-8 Copper 4.8E-02 4.5E-05 3.8E-02 3.6E-05 

100-41-4 Ethylbenzene 8.6E-01 8.1E-04 7.6E-01 7.2E-04 

50-00-0 Formaldehyde 3.6E-03 3.3E-06 1.3E-02 1.2E-05

7647-01-0 Hydrogen chloride 2.2E-03 2.1E-06 8.2E-04 7.7E-07

7783-06-4 Hydrogen sulfide 2.1E+00 2.0E-03 1.8E+00 1.7E-03 

7439-92-1 Lead 5.3E-02 4.9E-05 4.7E-02 4.4E-05 

7439-96-5 Manganese 1.2E-01 1.2E-04 2.1E-01 2.0E-04 

7439-97-6 Mercury 9.1E-03 8.5E-06 8.5E-03 8.0E-06 

7440-02-0 Nickel 6.7E-02 6.3E-05 6.0E-02 5.7E-05 

108-95-2 Phenol 7.6E-02 7.1E-05 4.6E-02 4.4E-05

7782-49-2 Selenium 1.3E-02 1.2E-05 1.2E-02 1.1E-05 

1330-20-7 Xylene (total) 8.6E-01 8.1E-04 7.6E-01 7.2E-04 

7440-66-6 Zinc 8.4E-01 7.9E-04 5.4E-01 5.0E-04 

Note: lb/MMcf = pounds per million cubic feet asphalt fumes, lb/MMBtu = pounds per million British thermal units a

 Bold italic values indicate that all test runs were below detection limit. b

 Source: Hansell and England, 1998. 

5.6.3 Coke Calcining 

Coke calcining is one of the processes tested by API and WSPA for which emissions factors were 

developed (Hansell and England, 1998). The average emissions factors for a coke calcining unit 

controlled with a spray dryer and fabric filter are presented in Table 5-11. 

Table 5-11. Summary of Emissions Factors for Controlled Coke Calcining 

CAS Number Substance 

Mean Emissions Factora

lb/ton cokeb lb/MMBtub

83-32-9 Acenaphthene 1.5E-08 4.4E-08 

208-96-8 Acenaphthylene 1.8E-08 5.6E-08 

75-07-0 Acetaldehyde 1.0E-03 3.1E-03 

107-02-8 Acrolein 3.4E-04 1.0E-03 

120-12-7 Anthracene 1.8E-08 5.4E-08 

(continued) 
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5-22 

Table 5-11. Summary of Emissions Factors for Controlled Coke Calcining (continued) 

CAS Number Substance 

Mean Emissions Factora

lb/ton cokeb lb/MMBtub

7440-36-0 Antimony 4.6E-05 1.4E-04 

7440-28-2 Arsenic 4.7E-06 1.5E-05 

7440-39-3 Barium 2.0E-05 6.1E-05 

71-43-2 Benzene 3.2E-04 1.0E-03 

56-55-3 Benzo(a)anthracene 8.7E-09 2.6E-08 

50-32-8 Benzo(a)pyrene 8.1E-09 2.4E-08 

205-99-2 Benzo(b)fluoranthene 8.1E-09 2.4E-08 

191-24-2 Benzo(g,h,i)perylene 8.1E-09 2.4E-08 

207-08-9 Benzo(k)fluoranthene 8.1E-09 2.4E-08 

7440-41-7 Beryllium 1.9E-06 6.0E-06 

7440-43-9 Cadmium 9.3E-06 2.9E-05 

18540-29-9 Chromium (hexavalent) 6.3E-07 2.1E-06 

7440-47-3 Chromium (total) 2.1E-05 6.9E-05 

218-01-9 Chrysene 1.3E-08 3.7E-08 

7440-50-8 Copper 9.3E-06 2.9E-05 

53-70-3 Dibenz(a,h)anthracene 8.1E-09 2.4E-08 

1746-01-6 Dioxin:4D 2378 1.1E-11 3.7E-11 

Dioxin:4D Other 1.4E-10 4.4E-10 

40321-76-4 Dioxin:5D 12378 9.6E-12 2.9E-11 

Dioxin:5D Other 8.5E-11 2.7E-10 

39227-28-6 Dioxin:6D 123478 9.9E-12 3.5E-11 

57653-85-7 Dioxin:6D 123678 1.4E-11 4.4E-11 

19408-74-3 Dioxin:6D 123789 1.3E-11 4.2E-11 

Dioxin:6D Other 6.4E-11 2.1E-10 

35822-46-9 Dioxin:7D 1234678 1.4E-10 4.2E-10 

Dioxin:7D Other 1.3E-10 4.1E-10 

3268-87-9 Dioxin:8D 1.8E-09 5.3E-09 

206-44-0 Fluoranthene 3.6E-08 1.1E-07 

86-73-7 Fluorene 5.6E-08 1.7E-07 

50-00-0 Formaldehyde 3.4E-04 1.0E-03 

51207-31-9 Furan:4F 2378 1.3E-11 4.2E-11 

Furan:4F Other 1.4E-10 4.4E-10 

57117-41-6 Furan:5F 12378 1.4E-11 4.4E-11 

57117-31-4 Furan:5F 23478 1.3E-11 4.1E-11 

Furan:5F Other 1.2E-10 3.8E-10 

(continued) 
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5-23 

Table 5-11. Summary of Emissions Factors for Controlled Coke Calcining (continued) 

CAS Number Substance 

Mean Emissions Factora

lb/ton cokeb lb/MMBtub

70648-26-9 Furan:6F 123478 2.4E-11 7.9E-11 

57117-44-9 Furan:6F 123678 2.2E-11 7.1E-11 

72918-21-9 Furan:6F 123789 9.2E-12 3.0E-11 

60851-34-5 Furan:6F 234678 2.0E-11 6.5E-11 

Furan:6F Other 1.5E-10 4.8E-10 

67562-39-4 Furan:7F 1234678 1.5E-10 4.8E-10 

55673-89-7 Furan:7F 1234789 2.6E-11 8.0E-11 

Furan:7F Other 5.2E-11 1.8E-10 

39001-02-0 Furan:8F 1.5E-10 4.1E-10 

193-39-5 Indeno(1,2,3-cd)pyrene 8.1E-09 2.4E-08 

7439-92-1 Lead 6.2E-05 1.9E-04 

7439-96-5 Manganese 4.6E-05 1.4E-04 

7439-97-6 Mercury 4.6E-05 1.5E-04 

91-20-3 Naphthalene 2.4E-06 7.3E-06 

7440-02-0 Nickel 9.1E-05 2.9E-04 

85-01-8 Phenanthrene 1.9E-07 5.7E-07 

7723-14-0 Phosphorus 4.7E-04 1.5E-03 

129-00-0 Pyrene 2.7E-08 7.9E-08 

7782-49-2 Selenium 4.7E-06 1.5E-05 

108-88-3 Toluene 5.3E-05 1.6E-04 

1330-20-7 Xylene (m,p) 3.1E-05 8.9E-05

95-47-6 Xylene (o) 4.5E-05 1.3E-04 

7440-66-6 Zinc 1.2E-04 3.7E-04 

Note: lb/ton coke = pounds per ton of petroleum coke, lb/MMBtu = pounds per million British thermal units 

Abbreviations: 4D 2378 = 2,3,7,8-Tetrachlorodibenzo-p-dioxin; 5D 12378 = 1,2,3,7,8-Pentachlorodibenzo-p-dioxin; 

6D 123478 = 1,2,3,4,7,8-Hexachlorodibenzo-p-dioxin; 6D 123678 = 1,2,3,6,7,8-Hexachlorodibenzo-p-dioxin; 6D 

123789 = 1,2,3,7,8,9-Hexachlorodibenzo-p-dioxin; 7D 1234678 = 1,2,3,4,6,7,8-Heptachlorodibenzo-p-dioxin; 8D 

= Octachlorodibenzo-p-dioxin; 4F 2378 = 2,3,7,8-Tetrachlorodibenzofuran; 5F 12378 = 1,2,3,7,8-

Pentachlorodibenzofuran; 5F 23478 = 2,3,4,7,8-Pentachlorodibenzofuran; 6F 123478 = 1,2,3,4,7,8-

Hexachlorodibenzofuran; 6F 123678 = 1,2,3,6,7,8-Hexachlorodibenzofuran; 6F 123789 = 1,2,3,7,8,9-

Hexachlorodibenzofuran; 6F 234678 = 2,3,4,6,7,8-Hexachlorodibenzofuran; 7F 1234678 = 1,2,3,4,6,7,8-

Heptachlorodibenzofuran; 7F 1234789 = 1,2,3,4,7,8,9-Heptachlorodibenzofuran; 8F = Octachlorodibenzofuran. a

 Emissions factors provided are for coke calcining controlled with a spray dryer and fabric filter. Bold italic values 

indicate that all test runs were below detection limit; underlined values indicate that more than 75% of the test 

runs were below the detection limit. b

 Source: Hansell and England, 1998. 

5.6.4 Blowdown Systems 

Blowdown systems are used during depressurization processes to recover liquids entrained in a process 

gas stream. The remaining uncondensed gases may be compressed and recovered for use as fuel gas or 

they may be vented to a thermal destruction device (thermal oxidizer or flare). Either of these scenarios 
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5-24 

would be considered a “controlled” blowdown system. In an “uncontrolled” blowdown system, the 

uncondensed gases are vented directly to the atmosphere. For blowdown gases that are recovered as fuel 

gas, the emissions from these gases would be accounted for in the emissions projected for stationary 

combustion devices (see Section 4). For blowdown gases that are vented to a flare, the emissions from 

these gases would be accounted for in the emissions projected for flares if Methodology Rank 1, 2, 3, or 4 

for flares is used (see Section 6). 

AP-42 (U.S. EPA, 1995a) contains default emission factors for uncontrolled blowdown systems as well as 

blowdown systems that recover the vapors for destruction in a flare. For systems controlled by a flare, the 

measurement methodologies provided in Section 6, Flares, should be used preferentially over these 

default emission factors, but these factors may provide an estimate of the portion of the flare’s emissions 

originating from blowdown gases. The AP-42 default emission factors for blowdown systems are 

provided in Table 5-12. For blowdown gases that are vented to control device other than a flare, use the 

methodologies for direct process vent measurement provided in this section, if appropriate data are 

available. If appropriate data are not available, use the emission factors for “blowdown systems with 

vapor recovery and flaring” in Table 5-12 for blowdown vents controlled with a thermal oxidizer, 

catalytic oxidizer, or similar combustion control system; for other control systems, use the uncontrolled 

blowdown default THC emissions factor provided in Table 5-12 and adjust for the efficiency of the 

control device using the default control efficiencies provided in Table 3-2 (Section 3, Storage Tanks). 

Table 5-12. Default Emissions Factors for Blowdown Systems 

Process Description Pollutant 

Emissions Factora 

(lb/103 barrel of refinery 

feed) Rating 

Uncontrolled blowdown Total hydrocarbonsb 580 C 

Blowdown System with 

vapor recovery and flaring 

Carbon monoxide 4.3 C 

Nitrogen oxides 19 C 

Sulfur dioxide 27 C 

Total hydrocarbonsb 0.8 C 

a

 Source: U.S. EPA, 1995a. 

b

 Total hydrocarbon may be estimated as a surrogate for VOC. (Overall, less than 1 weight % of total hydrocarbon 

emissions is methane.) 

5.6.5 Vacuum Producing Systems 

Vacuum producing systems include reciprocating, rotary or centrifugal blowers or compressors, or any jet 

ejector or device that takes suction from a pressure below atmospheric and discharges against atmospheric 

pressure. Depending on the vacuum producing system design, gases from the system may be released 

directly to the atmosphere or may be condensed, to the extent possible, using a condenser. The condensed 

liquid is gathered in a “hot well” or “accumulator” and the uncondensed gases are discharged to a control 

device or directly to the atmosphere. The vacuum producing system associated with the vacuum 

distillation of crude oil is typically the largest vacuum producing system at a petroleum refinery; vacuum 

producing systems may also be used to evacuate reactor vessels or vacuum trucks. AP-42 provides a total 

hydrocarbon emission factor for the vacuum distillation column condenser, which is provided in 

Table 5-13. Speciation of the gases can be estimated based on the composition in the condensed liquids 

and assuming the gases are saturated (in equilibrium) with the condensed liquid. If the emissions are 

controlled, a control device efficiency correction can be used to estimate the controlled emissions. 
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5-25 

Table 5-13. Default Emissions Factor for Vacuum Producing Systems 

Process Description Pollutant 

Emissions Factora 

(lb/103 barrel 

of vacuum feed) Rating 

Vacuum producing system 

on vacuum distillation 

column, uncontrolled 

Total hydrocarbonsb

 50 C 

a

 Source: U.S. EPA, 1995a. 

b

 Total hydrocarbon may be estimated as a surrogate for VOC. (Overall, less than 1 weight % of total 

hydrocarbon emissions is methane.) 
Version 2.1.1 

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6-1 

6. Flares 

Flares are point sources used at petroleum refineries to destroy organic compounds in excess refinery fuel 

gas, purged products, or waste gases released during startups, shutdowns, and malfunctions. Most flares 

have a natural gas pilot flame and use the fuel value of the gas routed to the flare to sustain combustion. If 

the heating value of the flare gas falls below certain values (for steam or air assisted flares, typically 300 

British thermal units per standard cubic feet [Btu/scf]), then natural gas may be added to the flare gas to 

maintain the appropriate heating value for good combustion. Emissions from flares consist of a fraction of 

the hydrocarbons in the flare gas (e.g., CH4, CO, VOC, and specific organic HAP) that are not combusted 

in the flare; SO2 resulting from the oxidation of sulfur compound impurities, such as H2S, in the gas 

stream; and CO2 from the combustion process. Flares are also expected to produce NOx emissions and 

may produce PM (soot) if combustion conditions are not adequate. A complete emissions inventory will 

include estimates for all these compounds (the specific organic HAP will vary based on the composition 

of the gas being flared). 

Accurate estimates of emissions from flares are difficult to obtain because they do not lend themselves to 

conventional emissions-testing techniques, and only a few attempts have been made to characterize flare 

emissions. Therefore, to date, there are limited direct emissions test data for flares. Recent developments 

in testing protocols, such as the DIAL technique, provide a direct emissions measurement technique for 

flares. However, DIAL measurements provide only a snapshot in time. Unless the flow and composition 

of the flare gas is highly stable, inaccuracies build as these measurements are extrapolated to annual 

emission rates. Continuous monitoring of the gas stream prior to combustion in the flare is generally the 

most accurate means of assessing flare emissions. One difficulty with this approach is that flare gas 

composition and flow are highly variable, and the monitors are calibrated to detect compositions or flows 

within a certain range or span, so if the flow or composition is outside the instrument’s range, then 

inaccuracies in the measurement data result. In addition, because the monitors are evaluating the stream 

of gas going to the flare, assumptions must be made regarding flare efficiency to determine the emissions 

following combustion. Engineering calculations are another methodology that can be used to assess 

certain release events. For example, if a pressure relief valve on a tank opens, then the volume of gas 

released can be calculated based on the pressure inside the tank, the pressure outside the tank, the crosssectional area of the valve opening, and the duration the valve is open (see Section 12, 

Malfunctions/Upsets, in this Refinery Emissions Protocol document. Product knowledge of the tank 

liquid composition can be used to calculate the equilibrium vapor space composition, which is assumed to 

be the composition of the gas vented. Some emission factors are available, but these have high 

uncertainty. EPA concludes that direct measurement methods are best used to develop site- or flarespecific emission factors or to verify the combustion efficiency of a specific flare under certain 

conditions; however, they are not particularly useful in developing an emissions inventory for flares. 

Table 6-1 summarizes the hierarchy of flare emissions estimation techniques. Within a given 

measurement method (or rank), there may be alternative methods for determining the constituent-specific 

emissions; these compositional analysis methods are provided in order of accuracy. Each refinery will 

likely use a mixture of different methods. For example, Methodology Rank 1 for flares may be used for 

events that are directly monitored and are fairly routine releases, but Methodology Rank 4 for flares may 

have to be used to estimate emissions for unusual events. The remainder of this section provides 

additional detail and guidance regarding the implementation of these methods. 
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6-2 

Table 6-1. Summary of Flare Emissions Estimate Methodologies 

Rank Measurement Method Additional Data Needed 

1 Continuous composition monitoring (or 

manual sampling at least once every 3 hours 

during flaring events) and continuous flow 

rate monitoring of the gas sent to the flare 

 Combustion efficiency (based on results of a direct 

measurement test, if available, or a default 

assumption) 

2 Continuous flow rate monitoring and daily or 

weekly compositional analysis  Representative sample (grab or integrated) 

 Assumed combustion efficiency 

3 Continuous flow rate and heating value 

monitoring  Emission factors based on heating value 

4 Engineering calculations  Process knowledge of units connected to flare (e.g., 

volume, composition of process streams) 

 Temperature and pressure monitoring data or other 

process operating data as needed 

 Assumed combustion efficiency 

5 Emission factors based on energy 

consumption  Flow estimates (not continuous) 

 Heat value estimates (not continuous) 

6 Default emission factors based on refinery or 

process throughput  Refinery or process throughput 

6.1 Methodology Rank 1 for Flares 

Methodology Rank 1 for flares includes continuously measuring composition and flow of gas sent to the 

flare. For flares that do not have routine flow, manual sampling of the flare gas at least once every 3 hours 

during each flaring event is also considered Methodology Rank 1 for flares. For a flare, the most likely 

pollutants to be estimated using Methodology Rank 1 are SO2 and total hydrocarbons (or VOC). For 

example, a reduced sulfur or total sulfur monitor can be used to characterize the sulfur content of the gas 

being combusted in the flare. Similarly, monitoring of the total hydrocarbon, VOC, or specific organic 

HAP content in the flare gas can be used to assess the emissions of these pollutants. However, because 

these monitors measure the concentrations in the gas sent to the flare rather than the gas exiting the flare, 

the other piece of information needed to estimate emissions from the flare is the flare efficiency (Feff). For 

the example of sulfur content above, the portion of the sulfur that is oxidized to SO2 emissions during the 

combustion of the flare gas will be dependent on the combustion efficiency. For emissions of compounds 

that are emitted as a result of incomplete combustion, such as reduced sulfur compounds and 

uncombusted hydrocarbons, one minus the assumed flare efficiency 

(1-Feff) is used to estimate the emission rate. 

As noted above, direct measurement methods are available and can be used to confirm the efficiency of a 

flare. If efficiency information is available for a specific flare at a refinery under certain conditions, that 

information should be used to estimate emissions for that flare where appropriate. For other flares, 

Section 13.5 of Compilation of Air Pollutant Emission Factors notes that the flare combustion efficiency 

for properly operated flares is at least 98% (U.S. EPA, 1995a). It is important to note that only flares that 

operate consistent with the criteria of 40 CFR 60.18 should be assumed to be “properly operating” and 

achieving 98% combustion efficiency. It should also be noted that recent efforts to better characterize 

flare emissions include efforts to determine whether this combustion efficiency continues to be 

appropriate for properly operated flares. At this time, sufficient data have not yet been collected and 

evaluated to support revising this efficiency estimate. 

Most gas composition monitors measure the concentration on a volume basis (and generally on a dry 

basis), although some will provide the concentration on a mass basis. Most flow monitors measure 
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6-3 

volumetric flow rate in actual cubic feet. Many flow monitoring systems are equipped with temperature 

and pressure monitors to automatically convert the flow to standard conditions. If the gas composition is 

determined on a dry basis, which is typical for extractive monitoring systems, then it is important to also 

correct the flow to be on a dry basis. The total volumetric flow of the pollutant can be converted to a mass 

emission rate using the molecular weight of the pollutant and/or the ideal gas law, as appropriate. An 

emissions estimate can be calculated using Equation 6-1, which is a variation of Equation 4-1 for CEMS: 

() ( ) [ ] ( )

100%

1 1

∑ 20

= ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

× × × × ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

×⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛ = × − ×

N

n

i n i

eff

o

n

n

o

i n H n K

MVC

C MW

K

P

P

T

T

E Q f (Eq. 6-1) 

where: 

 Ei = Emission rate of pollutant “i” (tons per year [tons/yr] or tons per event [tons/event]). 

 N = Number of measurement periods per year or per event (e.g., for hourly measurements, 

N = 8,760 to calculate annual emissions). 

 n = Index for measurement period. 

 (Q)n = Volume of gas sent to the flare for measurement period “n” (actual cubic feet [acf]). If 

the flow rate meter automatically corrects for temperature and pressure, then replace 

“(T)o ÷ (T)n × (P)n ÷ (P)o” with “1.” If the pollutant concentration is determined on a 

dry basis and the flow rate meter automatically corrects for moisture content, replace 

the term [1-(fH20)n] with 1. 

 (fH2O)n = Moisture content of exhaust gas during measurement period “n,” volumetric basis 

(cubic feet water per cubic feet exhaust gas). 

 To = Temperature at “standard conditions” (520 °R or 528 °R). 

 Tn = Temperature at which flow is measured during measurement period “n” (°R). 

 Pn = Average pressure at which flow is measured during measurement period “n” (atm). 

 Po = Average pressure at “standard conditions” (1 atm). 

 Keff = Factor to account for the efficiency of the flare. Keff is equal to the flare efficiency Feff

for pollutants created by combustion, such as SO2. Keff is equal to one minus the flare 

efficiency (1 – Feff) for pollutants in uncombusted gas, such as VOC, reduced sulfur, 

and specific HAP. 

 (Ci)n = Concentration of pollutant “i” or the appropriate precursor to pollutant “i” in the gas 

sent to the flare for measurement period “n” (volume %, dry basis). If the pollutant 

concentration is determined on a wet basis, then replace the term [1−(fH20)n] with 1. 

 MWi = Molecular weight of pollutant “i” (kilogram per kilogram mole [kg/kg-mol]). 

 MVC = Molar volume conversion factor (standard cubic feet per kilogram mole [scf/kg-mol]) 

 = 836.6 scf/kg-mol at “standard conditions” of 60°F (520°R) and 1 atmosphere (atm) 

 = 849.5 scf/kg-mol at “standard conditions” of 68°F (528°R) and 1 atm. 

 K = Conversion factor = 2.2046/2,000 (tons per kilogram [tons/kg] = 0.0011023 tons/kg. 

As explained in Section 4-1, a continuous monitor records multiple measurements per hour, and the 

individual measurements can be used to calculate annual emissions in two ways. For a flare, the selection 

of an hourly average approach or heavier reliance on individual measurements will depend on the 

duration of the flare’s operation (particularly for flares that operate only intermittently) and the process 

unit generating the gas being flared. 

6.2 Methodology Rank 2 for Flares 

Methodology Rank 2 for flares includes continuous monitoring of flare gas flow as in Methodology 

Rank 1 for flares and routine (daily or weekly) sampling and analysis to determine the composition of the 

flare gas. Methodology Rank 2 also includes determining composition by continuously monitoring a 

“surrogate” component, and then using sampling or other data to periodically check a correlation between 
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the surrogate and the pollutant. For a flare, the most likely pollutants to be estimated using Methodology 

Rank 2 for flares are SO2 and specific HAP. A continuous monitor for H2S can be used to estimate SO2

emissions similar to the process described for Methodology Rank 1, but because H2S is only one of 

several sulfur compounds potentially present in the flare gas, it is important to periodically characterize 

the total sulfur content of the gas so as not to underestimate SO2 emissions from the flare. For example, 

periodic sampling of the flare gas can be performed to determine the total sulfur content of the flare gas, 

which can be used in conjunction with the H2S monitoring data to determine an average total sulfur-toH2S ratio of the flare gas. This average total sulfur-to-H2S ratio, expressed in SO2 equivalence, can be 

used to adjust the H2S concentration measured by the continuous monitor to provide a more accurate and 

complete assessment of SO2 emissions from the flare. Similarly, sampling can be used to determine the 

relative concentration of specific HAP present in the flare gas. These sampling data can be used in 

conjunction with total hydrocarbon monitoring data to estimate HAP emissions from the flare. As with 

the Methodology Rank 1 for flares, the generation or destruction of pollutants in the flare will depend on 

the flare combustion efficiency. As mentioned previously, the current default flare combustion efficiency 

for properly operating flares is 98% (U.S. EPA, 1995a). 

6.3 Methodology Rank 3 for Flares 

Methodology Rank 3 for flares includes continuous monitoring of flare gas flow as in Methodology 

Rank 1 for flares, continuous monitoring of the heating value of the fuel, and emission factors based on 

the heating value. The most likely pollutants estimated using Methodology Rank 3 for flares are CO, 

NOx, and total hydrocarbons (surrogate for VOC). A general equation for Methodology Rank 3 for flares 

is as follows: 

∑( ) =

= × ×

N

n

Ei Qstd n LHVn EFi

1

, (Eq. 6-2) 

where: 

 Ei = Emission rate of pollutant “i” (lbs/yr or lbs/event). 

 N = Number of measurement periods per year or per event (e.g., for hourly measurements, 

N = 8,760 to calculate annual emissions). 

 n = Index for measurement period. 

 Qstd,n = Volume of gas sent to the flare for measurement period “n” (scfm). If the flow meter 

does not output flow at “standard conditions,” the Qstd,n can be calculated using the first 

four terms within the summation of Equation 6-1. Note: the “standard conditions” 

used for the volume of gas must match the “standard conditions” at which the heating 

value of the gas is determined. 

 LHVn = Heating value of gas being flared during measurement period “n” on a lower heating 

value (LHV) basis (MMBtu/scf). (Heating value for flares is usually determined on a 

lower (net) heating value (LHV) basis whereas heating value for process heaters and 

boilers are usually determined on a higher heating value basis.) 

 EFi = Emission factor for pollutant “i” (lb/MMBtu). 

Values for “EFi” are presented in Tables 6-2 and 6-3 below. It is important to note that both sets of 

emission factors are intended for use with properly operating flares meeting the criteria of 40 CFR 60.18; 

therefore, the flare efficiency is already included in these emission factors. It is also important to note that 

the number of components for which emission factors are available is limited because these emission 

factors are based on general combustion characteristics and limited emission tests. For example, the 

emission factors for NOx are generally based on the amount of nitrogen in the air during combustion, so if 

there are constituents containing nitrogen in the fuel gas, such as ammonia, additional calculations are 
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needed to account for all NOx emissions (based on Methodology Rank 2 for flares, particularly if flow 

rate is monitored continuously.) 

The emission factors in Table 6-2 are from Section 13.5 of EPA’s Compilation of Air Pollutant Emission 

Factors (U.S. EPA, 1995a, also known as AP-42) and have an emission factor rating of “B” (U.S. EPA, 

1995a, for details on the emission factor rating system). These flare emission factors are based on limited 

EPA tests conducted decades ago. Although AP-42 does not specify, it is common practice that the 

heating value for flares is determined on a LHV basis. As such, it is recommended that these emission 

factors be used with LHV heat content measurements. 

Table 6-2. Flare Energy Consumption-Based Emission Factors 

Component 

Emission Factora 

(lb/106 Btu, LHV basis) 

Total hydrocarbonsb 0.14 

Carbon monoxide (CAS No. 630-08-0) 0.37 

Nitrogen oxides 0.068 

a

 Source: U.S. EPA, 1995a. Assumes values are reported on a LHV basis. 

b

 Measured as methane equivalent. 

The emission factors in Table 6-3 are from Technical Supplement 4 of TCEQ’s 2008 Emissions 

Inventory Guidelines (TCEQ, 2009). The emission factor rating for these emission factors is not specified. 

These flare emission factors are intended to be used with LHV, or net heating value, heat content 

measurements. 

Table 6-3. TCEQ Energy Consumption-Based Emission Factors for Flares 

Component Assist Type 

Waste Gas Stream Net 

Heating Valuea Emission Factor(lb/MMBtu. LHV basis)b

Nitrogen oxides 

Steam 

High Btu 0.049 

Low Btu 0.068 

Air or Unassisted 

High Btu 0.14 

Low Btu 0.064 

Carbon monoxide 

(CAS No. 630-08-0) 

Steam 

High Btu 0.35 

Low Btu 0.35 

Air or Unassisted 

High Btu 0.28 

Low Btu 0.55 

a

 High Btu: > 1000 Btu/scf; Low Btu: 192–1000 Btu/scf b

 Source: TCEQ, 2009.

Additional emission factors for soot (i.e., PM) are also provided AP-42; however, the soot factors 

provided in units of concentration in the flare exhaust stream. These factors have been converted to 

heating value-based factors to allow calculation of soot (PM) emissions using Equation 6-2. To calculate 

the soot (PM) emissions from flares, each measurement period would be assigned a flare operation 

category based on the amount of smoke generated by the flare during that measurement period, so the 

appropriate emission factor could be applied. 
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Table 6-4. Emission Factors for Soot from Flares 

Flare Operation 

Emission Factora 

(μg/L in exhaust) 

Emission Factorb 

(lb/MMBtu, LHV basis) 

Nonsmoking flares 0 0.0 

Lightly smoking flares 40 0.027 

Average smoking flares 177 0.12 

Heavily smoking flares 274 0.19 

a

 Source: U.S. EPA, 1995a; reported as micrograms per liter (μg/L) in flare exhaust. b

 Calculated from concentration using F-factor method on a dry basis, assuming 3% O2 in exhaust 

gas stream.

6.4 Methodology Rank 4 for Flares 

Methodology Rank 4 for flares includes a variety of estimation methods based on engineering 

calculations. Estimates of nearly all pollutants from flares can be calculated using this rank based on 

process knowledge of units connected to the flare, including process unit volume, process stream 

compositions, temperature, and pressure. Any of this information used in conjunction with periodic 

sampling also constitutes Methodology Rank 4. The specific methods used will vary based on the ways in 

which the flare is used and the units the flare serves. Estimating emissions from flares with routine flow, 

such as those used for controlling blowdown from delayed coking units or other routine discharges, may 

rely on key process operating parameters that can be defined in advance. For process upsets or 

malfunctions, the estimation methods used may be very event-focused and are likely to rely on 

Example 6-1: Calculation of CO Emissions from a Flare with Continuous Monitors for 

Flow Rate and Heating Value 

Calculate hourly emissions from a refinery flare given: 

– The flaring event is from one source at the refinery and lasts several hours, so emissions 

can be estimated using the hourly average flow rate and heat content measurements 

– The average flow rate to the flare during a certain hour is 250 scfm 

– The higher heating value of the flow to the flare during that hour is 1200 Btu/scf, or 

1.2E-03 MMBtu/scf (1200 Btu/scf × 1E-06Btu/MMBtu) 

Calculate hourly emissions using Equation 6-2: 

( )

1

∑=

= ×××

N

n

CO Nnn EFMFRHV E CO

 ECO = (1.2E-03) × (250) × (60) × (0.37) 

 ECO = 6.7 lbs/hr 

If the flaring event lasts 3 hours, and the flow rate and heat content remained perfectly 

constant over those 3 hours, then the total emissions for that flaring event would be 6.7 lbs/hr 

× 3 hours = 20 lbs. Annual emissions for the flare would be calculated as the sum of emissions 

estimates for all events. 
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engineering judgment as much as actual monitoring data. Estimation methods may also be needed from 

flares with monitoring systems when an upset or malfunction causes the concentration or flow to exceed 

the calibrated span of the monitor. A few examples are described in this section, but many others are 

possible, given the complexity of refineries and differences between them. When emissions are estimated 

using Methodology Rank 4 for flares, a description of the methodology, assumptions, and specific pieces 

of data should be recorded and kept for future reference, both to document the emissions calculation 

methodology and to ensure consistency from one estimate to the next for a particular process. 

For routine or planned releases from flares not equipped with a continuous monitor, the refiner should 

know the quantity and composition of the gas being released. If the gas is excess fuel gas that has been 

amine-treated and mixed in a central drum, then the H2S concentration of the gas being flared should be 

the same as the concentration going to any fuel gas combustion device (e.g., process heater, boiler) at the 

refinery. (As noted previously, it is important to note that H2S may not be the only reduced sulfur 

compound contributing to SO2 emissions.) Alternatively, if a fuel gas combustion device has an 

instrument for measuring SO2 emissions, then the SO2 emissions from the flare can be calculated based on 

the quantities of gas being combusted in the fuel gas combustion device and the flare. If the efficiency of 

that fuel gas combustion device and the flare are not the same, then an efficiency correction may be 

needed. (This method would account for all sulfur from the flare since SO2 emissions would be measured 

directly.) As another example, if a refiner is emptying a tank and combusting the vapors, VOC and HAP 

emissions can be calculated based on the composition of the tank contents and the size of the tank. 

For emergency flares and flares with flare gas recovery systems (or otherwise equipped with water seals 

intended to prevent gases from going to the flare during normal operations), an alternative method of 

estimating flow rate for non-routine flaring events is to monitor the pressure drop across the flare water 

seal drum. A limited number of flow measurements can be made at different flare gas and water seal 

differential pressures (or water heights) to develop a flow rate correlation with the measured pressure 

drop. The water seal differential pressure or water height is routinely measured to determine the flow to 

the flare. Alternatively, the pressure in the flare line can also be monitored using a direct pressure monitor 

installed at the final liquid knock-out drum prior to the water seal. Concentrations of specific compounds 

are estimated by sampling and analysis of the flare gases (preferred, if possible) or calculations based on 

the composition of the gases in the process unit(s) contributing to the flaring event. Emissions are then 

calculated using those concentrations, the calculated flow rate, and an assumed flare efficiency. Some 

refiners that use this method for flares with a flare gas recovery system also monitor the recovery system 

to ensure that gases are not sent to the flare during normal operation. 

6.5 Methodology Ranks 5 and 6 for Flares 

As previously mentioned, flares are difficult to test, so only a few emission factors have been developed 

for flares. Available emission factors for flares were provided in Tables 6-2, 6-3, and 6-4 for use with 

continuous flow and heat content monitoring. Methodology Rank 5 for flares consists of using these same 

emission factors, but with estimates of the flow rate and heating content of the flare gas rather than direct 

measurement of these values. The total hydrocarbon emission factor could be used with knowledge of the 

components in the flare gas to estimate HAP emissions. 

Methodology Rank 6 for flares includes emission factors for HAP that were developed for the Petroleum 

Refinery Source Characterization and Emission Model for Residual Risk Assessment (RTI, 2002) based 

on the State of Louisiana’s title V permit applications data. The original emission factors presented in 

RTI’s document (2002) were based on arithmetic averages. However, the arithmetic average is 

occasionally skewed by one high estimate. The log-mean average emission factors from the State of 

Louisiana’s title V permit applications data were calculated and are provided in Table 6-5. These 

emission factors yield a cumulative emission estimate from all flares (not per flare) for the refinery based 

on the total refinery crude capacity in barrels per calendar day (bbl/cd). It is uncertain how the permit 
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application estimates were developed and whether these estimates include SSM events, but it is likely that 

these factors would not include emissions released during significant SSM events. As such, these 

emission factors are very general and are not recommended unless no other information is available. 

Refineries are expected to have more source-specific information for estimating flare emissions, but these 

factors may be used for the purposes of modeling or for general emissions estimates. 

Table 6-5. Flare General Emission Factorsa

CAS Number Component 

Emission Factor 

(tons/yr/bbl/cd) 

71-43-2 Benzene 9 E-06 

108-88-3 Toluene 7 E-06 

1330-20-7 Xylene 6 E-06 

1634-04-4 Methyl tertiary-butyl ether 3 E-06 

110-54-3 Hexane 1 E-05 

50-00-0 Formaldehyde 1 E-06 

100-41-4 Ethylbenzene 2 E-07 

106-99-0 1,3-Butadiene 7 E-06 

a

 Source: Log-mean average from State of Louisiana’s title V permit 

applications data 

The application of these emission factors is straightforward, using Equation 6-3. 

i = × EFCapE i (Eq. 6-3) 

where: 

 Ei = Mass emissions per year of pollutant “i” (tons/yr) 

 Cap = Crude capacity of refinery (bbl/cd) 

 EFi = Emission factor for pollutant “i” (tons/yr/bbl/cd) 

Example 6-2 shows the calculation of emissions from flares at a refinery with a given crude capacity. 

Example 6-2: Emissions Factor 

Given that a refinery has a crude capacity of 100,000 bbl/cd crude capacity, the annual 

emissions of benzene (C6H6) emissions can be calculated from flares at the refinery as follows: 

HC 66 HC 66 = × EFCapE

EC6H6 = (100,000) × (9E-06) 

EC6H6 = 0.9 tons/yr 
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7. Wastewater Collection and Treatment Systems 

Industrial wastewater collection and treatment operations range from simple pre-treatment operations that 

discharge to publicly owned treatment works (POTW) to full-scale wastewater treatment systems. Fullscale treatment systems include the collection of process and/or storm water that is treated to a quality 

that is acceptable for discharge to a receiving water body or for re-use. 

Wastewater collection systems differ among facilities, but they generally include drains, manholes, 

trenches, lift stations, sumps, junction boxes, and weirs. As water passes through each of these system 

components, emissions may occur by volatilization of organic compounds at the water/air interface. 

The overall objectives of wastewater treatment at refineries are to: (1) equalize flow and pollutant load by 

buffering flow surges in large tanks, (2) separate free and emulsified oils and solids from the wastewater 

by oil/water separators and flotation unit operations (e.g., dissolved air flotation [DAF], induced air 

flotation [IAF], dissolved nitrogen flotation [DNF]), and (3) oxidize organic molecules and remove or 

transform nutrients through biodegradation. Figure 7-1 shows a typical full-scale refinery wastewater 

treatment scheme. 

Figure 7-1. Typical refinery wastewater treatment system. 

Tanks or treatment units upstream of any benzene removal or destruction systems (e.g., stream strippers, 

enhanced biodegradation units) at most petroleum refineries are regulated under BWON (Benzene Waste 

Operations NESHAP) and thus should be covered and vented to appropriate control devices. Equalization 

tanks, oil/water separators, and flotation units typically fall into this category; however, in the event these 

units are not covered because they do not contain high benzene quantities, emission estimation methods 

are presented in this Refinery Emissions Protocol document. Biological treatment units are typically the 

first uncovered process in the wastewater treatment system and thus the first air emission source. 

Table 7-1 lists the emission estimation methods for wastewater treatment systems. The methods are 

ranked according to anticipated reliability. There are three primary estimation methods: (1) direct 

measurement, (2) predictive modeling, and (3) engineering estimates. Direct measurements can only be 
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7-2 

taken from process units that are covered and vented to a control device. Predictive modeling can be 

accomplished using analytical equations, such as those presented in AP-42, by using computer-based fate 

and transport models (e.g., WATER9, TOXCHEM), or by using the simplified refinery wastewater 

emission tool (RWET) presented in this Refinery Emissions Protocol document. Engineering estimates 

can be made using emission factors based on crude throughput or wastewater load. 

Table 7-1. Summary of Wastewater Treatment Emission Estimates 

Rank Measurement Method Application Data Requirements 

1 Direct measurement Covered and 

vented units 

 Constituent load and speciation of collected 

gas samples 

2a Predictive modeling with sitespecific factors and 

biodegradation rates followed by 

validation 

Uncovered units  Constituent load and speciation of process 

wastewaters 

 Site-specific biodegradation rates 

 Model validation by a direct measurement 

method 

2b Predictive modeling with sitespecific factors and 

biodegradation rates 

Uncovered units  Constituent load and speciation of process 

wastewaters 

 Site-specific biodegradation rates 

2c Predictive modeling with sitespecific factors 

Uncovered units  Constituent load and speciation of process 

wastewaters 

3a Engineering estimates based on 

wastewater treatment plant load 

Uncovered units  Constituent load and speciation of process 

wastewaters 

3b Engineering estimates based on 

crude throughput 

Uncovered units  Crude throughput 

7.1 Methodology Rank 1 for Wastewater Treatment Units 

Emissions from covered and vented wastewater treatment units and drainage system components can be 

directly measured using CEMS or periodic sampling; emission inventory estimates for these vented 

sources can be developed using the methods summarized in Section 4, Stationary Combustion Sources, 

and Section 5, Process Vents, of this Refinery Emissions Protocol document. 

Although there are direct measurement methods for uncovered units (i.e., off gas collectors and open path 

optical methods such as DIAL), these methods do not provide continuous monitoring data. Therefore, 

these methods are not recommended as primary techniques for emission estimations, but are reasonable 

for predictive modeling validation. 

7.2 Methodology Rank 2 for Wastewater Treatment Units 

Air emission estimation modeling techniques use mathematical equations to predict the fate and transport 

of specific constituents in wastewater. This section describes some key wastewater treatment units and the 

applicable methods for estimating the emissions from these units. Wastewater collection systems are 

considered an initial wastewater treatment unit to account for the emissions. 

Although successful use of the available predictive models has been demonstrated, reporting facilities 

have expressed concerns regarding complexity, user friendliness, and accuracy; therefore, a simplistic 

refinery wastewater emission tool (RWET) has been developed as part of this document to address these 

issues and provide more accurate comparisons among refineries. RWET was designed to help the user 

identify critical model inputs for each process unit, recognize variables and constants that may be sitespecific, and calculate air emissions and constituent effluent concentrations. Additionally, constituent 

effluent concentrations from a treatment unit can be used as inputs for the next downstream unit when 

processes are linked in a series (e.g., oil-water separator effluent data equals input data for the DAF unit). 
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The “Critical Inputs” section of the refinery wastewater emission tool includes data that is required to 

estimate air emissions from the specific process unit. The “Variables with Default Values” section 

includes inputs that may be site-specific or unknown to the user. Default values are taken from AP-42, but 

they can be changed if more accurate data are known or determined. The Chemical Properties sheet 

contains the best available chemical, physical, and biodegradation information on the 30 organic HAP 

listed in the Petroleum Refinery MACT I. However, if more accurate or site-specific data are available, 

then these data can be inserted in the Site-Specific Table on the Chemical Properties sheet, and the model 

will override the default values. Detailed instructions for use and application are provided in the refinery 

wastewater emission tool. 

Since reliable variables to estimate emissions for all volatile organic compounds (VOC) are not available, 

air emission estimates for compounds not listed in the MACT I can be made using surrogate compounds. 

Butane is the surrogate compound used for C2 – C4 VOC and octane for C4 – C9 in the refinery 

wastewater emission tool. Air emission estimates for compounds not listed and considered non-volatile 

(e.g., > C9 and Henry’s law constant > 10-3 atm-m3

/gmol) can be made using the Compound A, B, or C 

rows in the tool. The following list of chemical, physical, and biological degradation properties for each 

compound are required to reliably estimate air emissions: 

1. Molecular weight 

2. Vapor pressure 

3. Henry’s law constant 

4. Diffusivity in water 

5. Diffusivity in air 

6. Octanol-water partitioning coefficient 

7. Maximum biorate constant 

8. Half saturation biorate constant 

The calculations used in RWET and variable definitions are based on those presented in AP-42 and on 

peer-reviewed journals and are presented in detail in Appendix B, Wastewater Treatment System 

Equations, of this Refinery Emissions Protocol document. RWET is available for free at the following 

EPA website: http://www.epa.gov/ttn/chief/efpac/esttools.html. 

7.2.1 Wastewater Collection Systems 

Wastewater collection systems are complex networks of various components that drain large surface 

areas. These complexities make accurately estimating air emissions a very challenging task. RWET 

utilizes process drainage areas (PDAs), shown schematically in Figure 7-2, to more-easily estimate air 

emissions. Rather than summing all of the drains and other components within the processing area, model 

drainage systems are developed for each PDA. The model drainage components are based on the typical 

(or reasonable worst-case) components that an individual waste stream will experience. In the top 

drainage area of Figure 7-2, an individual waste stream would experience typically two drains (or, for a 

worst-case assessment, three drains), one junction box, one manhole cover, and a lift station. For the 

lower drainage area of Figure 7-2, an individual waste stream in this area would experience typically two 

drains (or, for a worst-case assessment, three drains), a length of open trench (from either the middle or 

furthest most drain for the typical or worst-case assessment, respectively), one sump, and a lift station. 

Each of the model drainage system components may be identified as either controlled or uncontrolled. 

Components meeting the requirements for controlled drainage components in BWON are considered 

controlled components. The drainage components do not necessarily have to be subject to BWON to be 
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considered controlled, only that the specified controls are used (e.g., water seals for drains, gasketed 

manhole covers, or drainage systems vented to a control device). 

For each PDA, the wastewater generation rate and pollutant concentration at the point of generation 

(POG) are needed to determine the pollutant load to the system. Model drainage components, constituent 

load, and control efficiencies are then utilized within RWET to estimate air emissions for a given PDA. 

The emissions from each PDA are then combined to obtain the total for the wastewater collection system. 

More details of this method are presented in Appendix B, Wastewater Treatment System Equations. 

Table 7-2 lists the critical inputs, variables with default values, and chemical properties specific to 

wastewater collection system PDAs. 

As previously stated, RWET utilizes model drainage system components to ease the complexity of 

estimating air emissions from collection systems. However, if system components (e.g., lift stations, 

junction boxes, and sumps) vary greatly from those described in the Best Available Control Technology/ 

Lowest Achievable Emission Rate (BACT/LAER), site-specific air emissions can be determined from the 

procedures described in Appendix B, Wastewater Treatment System Equations. 

Figure 7-2. Typical refinery wastewater collection system process drainage areas. 
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Table 7-2. Critical Inputs and Chemical Properties Specific to Wastewater Collection System 

PDA Air Emission Calculations 

Critical Inputs Variables with Default Values Chemical Properties 

Number of drains Controlled / Uncontrolled Henry’s Law Constant (H) 

Linear meters of open trench Control Efficiency 

Number of manholes 

Number of junction boxes 

Number of lift stations 

Number of sumps 

Wastewater flow rate (Q) 

Constituent concentration at POG (C0) 

7.2.2 Primary Weirs 

Weirs can serve as open-channel dams and utilized in settling basins to discharge cleaner effluent. As 

previously stated, these components of the wastewater collection system are typically covered and vented; 

therefore, open-air emission estimations are not required. However, if the treatment units are uncovered, 

then the refinery wastewater emission tool can be used to estimate air emissions. Table 7-3 lists the 

critical inputs, variables with default values, and chemical properties specific to weirs. 

Table 7-3. Critical Inputs, Variables, and Chemical Properties Specific 

to Primary Weir Air Emission Calculations 

Critical Inputs Variables with Default Values Chemical Properties 

Wastewater flow rate (Q) Diffusivity of oxygen in water (DO2,w) Diffusivity of constituent in water (Dw) 

Constituent influent concentration (C0) 

Weir height (h) 

7.2.3 Oil-Water Separators 

An oil-water separator is a treatment unit designed to separate oil and suspended solids from wastewater. 

As previously mentioned, these treatment units are typically covered and vented; therefore, open-air 

emission estimations are not required. However, if the treatment units are uncovered, then the refinery 

wastewater emission tool can be used to estimate air emissions. Table 7-4 lists the critical inputs, 

variables with default values, and chemical properties specific to oil-water separators. 

If an oil-water separator is covered except for the effluent weir, air emissions can be calculated by using 

the methods described in Section 7.2.3 (primary weirs) and the associated sheet in RWET. 

Table 7-4. Critical Inputs, Variables, and Chemical Properties Specific 

to Oil-Water Separators Air Emission Calculations 

Critical Inputs Variables with Default Values Chemical Properties 

Surface area (A) Flow of oil (Qoil) Diffusivity of constituent in air (Da) 

Oil layer thickness (Olayer) Density of oil (ρoil) Octanol–water partitioning coefficient 

(Kow) 

Total pressure (P0) Molecular weight of oil (MWoil) Vapor pressure of constituent (P*) 

Wastewater flow rate (Q) Density of air (ρair) 

Constituent influent concentration (C0) Molecular weight of air (MWair) 

Wind speed (U10) Viscosity of air (μa) 

 Fraction of volume that is oil (FO) 
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7.2.4 Dissolved Air Flotation Units 

DAF is a wastewater treatment unit that uses bubble flotation to remove suspended oil and solids from 

water. As previously mentioned, these treatment units are typically covered and vented to control devices. 

However, if the treatment units are uncovered, then the refinery wastewater emission tool can be used to 

estimate air emissions. Table 7-5 lists the critical inputs, variables with default values, and chemical 

properties specific to DAF units. 

Table 7-5. Critical Inputs, Variables, and Chemical Properties Specific 

to DAF Air Emission Calculations 

Critical Inputs Variables with Default Values Chemical Properties 

Surface area (A) Viscosity of water (μL) Diffusivity of constituent in air (Da) 

Temperature (T) Density of water (ρL) Diffusivity of constituent in water (Dw) 

Total pressure (P0) Molecular weight of water (MWL) Henry’s law constant (H) 

Wastewater flow rate (Q) Density of air (ρair) 

Constituent influent concentration (C0) Molecular weight of air (MWair) 

Diffused air flow rate (Qa) Viscosity of air (μa) 

Wind speed (U10) 

7.2.5 Equalization Tanks 

Equalization tanks dampen variations in wastewater flow rate and pollutant load to lessen negative 

impacts on downstream processes. As previously mentioned, these tanks are commonly covered and 

vented to control devices; however, if the treatment units are uncovered, then the refinery wastewater 

emission tool can be used to estimate air emissions. Table 7-6 lists the critical inputs, variables with 

default values, and chemical properties specific to equalization tanks. 

Table 7-6. Critical Inputs, Variables, and Chemical Properties Specific 

to Equalization Tank Air Emission Calculations 

Critical Inputs Variables with Default Values Chemical Properties 

Surface area (A) Density of water (ρL) Diffusivity of constituent in air (Da) 

Temperature (T) Viscosity of water (μL) Diffusivity of constituent in water 

(Dw) 

Total pressure (P0) Density of air (ρair) Henry’s law constant 

Wastewater flow rate (Q) Molecular weight of air (MWair) 

Constituent influent concentration 

(C0) 

Viscosity of air (μa) 

Wastewater depth (D) Rotational speed of impeller (w) 

Total power to aerators (Ptot) Quiescent surface area (AQ) 

Number of aerators (NI) Oxygen transfer correction factor 

(Ot) 

Turbulent surface area (AT) Oxygen transfer rating to surface 

area (J) 

Wind speed (U10) Impeller diameter (d) 

7.2.6 Biological Treatment Units 

Biological treatment is an effective process to reduce, remove, or transform organic constituents and 

nutrients typically found in refinery wastewater to an acceptable form or concentration prior to discharge 

or re-use. However, biological treatment units are complex and vary greatly in design, operation, and 
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treatment efficiency, resulting in units that are difficult to characterize. Multiple fate and transport 

mechanisms are often involved in the ultimate removal of a specific compound. As seen in Figure 7-3, 

biodegradation, volatilization, adsorption, hydrolysis, and photo degradation are common mechanisms in 

wastewater treatment that may compete against each other. Additionally, biological systems are dynamic 

in nature, resulting in shifts in the dominant fate mechanism. Therefore, it is important to obtain and use 

site-specific variables when estimating emissions to obtain accurate results. 

Biological 

Treatment Unit

Reactions and 

Absorption

Constituent In (Wastewater)

Constituent Out 

(Wastewater)

Constituent Out 

(Sludge)

Figure 7-3. Simplified drawing of a constituent mass balance in a biological treatment unit. 

The two primary classes of biological treatment units are suspended-growth and attached-growth systems. 

Suspended-growth systems maintain the biomass (flocs) in suspension by mechanical or aeration devices 

where biodegradation occurs. Examples of suspended-growth systems include activated sludge, aerated 

lagoons, sequencing batch reactors, and membrane bioreactors. Attached-growth systems establish 

biofilms on fixed surfaces where biochemical reactions occur. Examples of attached-growth systems 

include trickling filters, rotating biological contactors, and fluidized-bed reactors. Regardless of the type 

of biological treatment used, the biochemical reactions are generally the same, with the oxidation of 

organic compounds and ammonia forming new cells, CO2, and water. 

To maintain the health of the microorganisms and ensure adequate biologically mediated oxidation of the 

organic compounds and ammonia, O2 must be introduced into the system. There are two basic methods 

for aerating wastewater: (1) introducing air or pure O2 into the wastewater through diffusers or other 

devices, and (2) agitating the water to increase surface area and promote the gaseous exchange with the 

atmosphere. However, the mechanisms that increase dissolved oxygen concentration in the water also 

increase the emission rate of organic constituents through increased volatilization. The volatilization rate 

can be affected by the wastewater surface area, turbulence, and temperature; hydraulic retention; water 

depth; concentration and physical properties of the organic constituents (e.g., volatility, diffusivity, 

inhibitory mechanisms); and atmospheric conditions. 

As previously mentioned, the biological treatment unit will most likely be the first uncovered process in 

the wastewater treatment system and potentially the greatest source of air emissions. Table 7-7 lists the 

critical inputs, variables with default values, and chemical properties specific to biological treatment unit 

air emission calculations. 
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Table 7-7. Critical Inputs, Variables, and Chemical Properties Specific 

to Biological Treatment Unit Air Emission Calculations 

Critical Inputs Variables with Default Values Chemical Properties 

Surface area (A) Density of water (ρL) Diffusivity of constituent in air (Da) 

Temperature (T) Viscosity of water (μL) Diffusivity of constituent in water 

(Dw) 

Total pressure (P0) Density of air (ρair) Henry’s law constant 

Wastewater flow rate (Q) Molecular weight of air (MWair) Maximum biodegradation rate 

constant (Kmax) 

Constituent influent concentration 

(C0,X) 

Viscosity of air (μa) Half saturation biorate constant (Ks) 

Wastewater depth (D) Weight fraction of the total carbon in 

biomass (fOC) 

Octanol-water partitioning 

coefficient (Kow) 

Total power to aerators (Ptot) Quiescent surface area (AQ) 

Number of aerators (NI) Oxygen transfer correction factor 

(Ot) 

Mixed liquor volatile suspended 

solids (CMLVSS) 

Oxygen transfer rating to surface 

area (J) 

Influent BOD concentration (C0,BOD) Impeller diameter (d) 

Wind speed (U10) Rotational speed of impeller (w) 

Turbulent surface area (AT) Biomass volatile suspended solids 

yield from influent biochemical 

oxygen demand (Y) 

Wasted sludge flow rate (Qw) 

7.2.7 Polishing Ponds 

Although air emissions downstream of biological treatment should be minimal, ineffective treatment, 

constituent slugs, or hydraulic surges may lead to HAP contamination of tertiary treatment processes (i.e., 

polishing ponds). If air emission estimates are needed for polishing ponds, then the equalization tank 

sheet of the refinery wastewater emission tool can be used. Although polishing ponds may function as a 

plug-flow reactor, the assumption can be made that volatilization is the major constituent fate mechanism. 

If the polishing pond is aerated and has significant active biomass (> 40 milligrams per liter [mg/L] 

volatile suspended solids), the biological treatment sheet of the model may be used. 

7.2.8 Site-Specific Factors 

There has been tremendous effort to compile default values for specific variables to estimate air 

emissions; however, site-specific data provide the most accurate results. The factors that can have the 

most dramatic impact on air emissions from a biological treatment unit are the ones impacting 

biodegradation. Compound-specific biodegradation rate constants (i.e., k0 and k1) and the half-saturation 

concentration (i.e., KS) can be determined by using the aerated reactor test (BOX test). The empirically 

derived values can then be used in a predictive model for more accurate results than can be developed 

when default biodegradation rate constant values are use. The methods used to determine the fraction of 

organic constituent biodegraded are provided in 40 CFR Part 63, Appendix C (also available at: 

http://www.epa.gov/EPA-AIR/2004/June/Day-30/a14826.htm). 

Although these methods have been successfully used to estimate biodegradation rates, there are concerns. 

Specifically, it is argued that dosing the bioreactor with only one constituent of interest yields inaccurate 

biodegradation rates compared to those dosed with a mixture of compounds commonly encountered by 

the microorganisms. Preferential biodegradation, degradation by-products, and co-metabolism are 
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important factors to consider when determining biodegradation rates that are not addressed in the 

recommended methods. Yerushalmi and Guiot (1998) reported biodegradation rates of benzene and 

toluene that were 62.9 and 16.4 times greater, respectively, when used as the sole substrate, versus a 

mixture of organic compounds. It is recommended that the constituent of interest be dosed in the 

appropriate ratio with organic compounds found in the real-world system (as described in Appendix C). 

Additionally, the methods do not distinguish between biodegradation, hydrolysis, and adsorption. Rather, 

the results of the BOX test are a summation of the three primary fate mechanisms common to aerated 

bioreactors. This fact is important to consider when assessing all the fate mechanisms involved in 

compound degradation. 

7.2.9 Model Validation 

To ensure that predictive model outputs are accurate, validation studies can be conducted to support the 

results. This task is accomplished by secondary direct or in-direct measurement techniques such as offgas 

collectors, DIAL, concentration-profile methods. Direct measurements are taken of a modeled process 

unit, and the results are compared. Favorable comparisons are indicative of accurate predictive modeling, 

whereas poor comparisons could be the result of incorrect assumptions or errors in the model. If 

corrective actions are necessary, a review of the constants and site-specific variables should be conducted. 

7.3 Methodology Rank 3 for Uncovered Units 

7.3.1 Engineering Estimates Based on Wastewater Treatment Plant Load 

If a facility only has benzene wastewater concentration data, then this method can be used to estimate the 

unknown HAP concentrations for use in the predictive modeling methods in Section 7.2, Methodology 

Rank 2 for Uncovered Units. The wastewater generation rates, benzene concentrations, and total HAP 

concentrations presented in Table 7-8 (U.S. EPA, 1998a) were combined with the total U.S. refinery 

processing and production capacities reported by EIA (2009) to calculate an average wastewater mixture 

to determine an average benzene and total HAP concentration of refinery wastewater. These data were 

evaluated using the average petroleum stream composition provided in Appendix B, Wastewater 

Treatment System Equations, of this Refinery Emissions Protocol document and an evaluation of the log 

octanol water partition coefficient to help speciate the total HAP concentration before and after oil 

removal. The results of this analysis (see Table 7-9) are relative concentrations of key pollutants as a ratio 

of the benzene concentration. If the benzene concentration of the refinery wastewater is known, then the 

concentration of other organics in the wastewater can be estimated using the ratios in Table 7-9. 

7.3.2 Engineering Estimates Based on Process Capacities 

Facilities that do not have any of the required data to estimate air emissions (e.g., for proposed units) can 

use the factors in Table 7-8 to estimate wastewater generation rates and benzene concentrations to the 

wastewater treatment system. Either the factors in Table 7-8 can be used to estimate the total organic 

HAP concentration, or the factors in Table 7-9 can be used to estimate the specific HAP (and total HAP) 

concentrations of the wastewater. The generated data can then be used to estimate specific constituent 

wastewater loads (see Section 7.3.1, Engineering Estimates Based on Wastewater Treatment Plant Load) 

and used in the predictive modeling methods in Section 7.2, Methodology Rank 2 for Uncovered Units. If 

the wastewater treatment system design is unknown, then the default emission factors in Table 7-10 can 

be used to estimate the fraction of the total constituent load to the wastewater treatment system 

(calculated using the factors in Tables 7-8 and 7-9) that is expected to be released into the atmosphere. 
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Table 7-8. Model Process Unit Characteristics for Petroleum Refinery Wastewatera

Process Unit 

Average Flow 

Factorb

(gal/bbl) 

Average Benzene 

Concentrationc

(ppmw) 

Average Organic 

HAP Concentration 

(ppmw) 

Crude distillation 2.9 21 140 

Alkylation unit 6 3 6.9 

Catalytic reforming 1.5 106 238 

Hydrocracking unit 2.6 14 72 

Hydrotreating/hydrorefining 2.6 6.3 32 

Catalytic cracking 2.4 13 165 

Thermal cracking/coking 5.9 40 75 

Thermal cracking/visbreaking 7.1 40 75 

Hydrogen plant 80d 62 278 

Asphalt plant 8.6 40 75 

Product blending 2.9 24 1,810 

Sulfur plant 9.7e 0.8 3.4 

Vacuum distillation 3 12 53 

Full range distillation 4.5 12 65 

Isomerization 1.5 33 117 

Polymerization 3.5 0.01 0.04 

MEK dewaxing units 0.011 0.1 27 

Lube oil/specialty processing unit 2.5 40 75 

Tank drawdown 0.02 188 840 

Note: gal/bbl = gallons of wastewater per barrel of capacity at a given process unit, ppmw = parts per million by 

weight a

 Source: U.S. EPA, 1998. 

b

 All flow factors were derived from Clean Air Act Section 114 questionnaire responses 

c

 Average concentration in the wastewater 

d

 This flow factor is given in gallons per million cubic feet (gal/MM ft3) of gas production e

 This flow factor is given in gal/ton of sulfur 

Table 7-9. Refinery Wastewater Contaminant Concentrations as a Ratio to Benzene 

CAS No. HAP 

Mass Concentration Ratio of Compounds 

to the Concentration of Benzene 

Inlet to Oil-Water 

Separator or DAF Unit 

Inlet to Biological 

Treatment Unit (After OilWater Separator) 

540841 2,2,4-Trimethylpentane 1.97 0.022 

71432 Benzene 1.00 1.00 

92524 Biphenyl 0.034 0.0005 

1319773 Cresols 0.25 0.38 

98828 Cumene 0.37 0.013 

100414 Ethylbenzene 0.88 0.086 

110543 Hexane 3.50 0.047 

(continued) 
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Table 7-9. Refinery Wastewater Contaminant Concentrations as a Ratio to Benzene (continued) 

CAS No. HAP 

Mass Concentration Ratio of Compounds 

to the Concentration of Benzene 

Inlet to Oil-Water 

Separator or DAF Unit 

Inlet to Biological 

Treatment Unit (After OilWater Separator) 

1634044 Methyl tertiary-butyl ether 0.58 0.98 

91203 Naphthalene 0.29 0.02 

108952 Phenol 0.18 0.80 

100425 Styrene 0.58 0.09 

108883 Toluene 3.3 0.80 

1330207 Xylene 3.6 0.33 

106990 1,3-Butadiene 0.0006 0.0027 

VOC Total VOCs 81 17 

Table 7-10. Default Mass Emission Factors for Refinery Wastewater Collection 

and Treatment Systems 

CAS No. HAP 

Mass Fraction of Compound Emitted from 

Wastewater Collection and Treatment System Based 

on Total Wastewater Loading 

Open Wastewater 

Collection and 

Treatment System 

BWON-Compliant 

Wastewater Collection 

and Treatment System 

106990 1,3-Butadiene 0.91 0.75 

540841 2,2,4-Trimethylpentane 0.95 0.55 

71432 Benzene 0.65 0.25 

92524 Biphenyl 0.34 0.031 

1319773 Cresols 0.002 0.000 

98828 Cumene 0.68 0.24 

100414 Ethylbenzene 0.66 0.22 

110543 Hexane 0.97 0.55 

1634044 Methyl tertiary-butyl ether 0.45 0.091 

91203 Naphthalene 0.41 0.098 

108952 Phenol 0.000 0.000 

100425 Styrene 0.81 0.64 

108883 Toluene 0.66 0.19 

1330207 Xylene 0.64 0.21 

VOC Total VOCs (using butane) 0.94 0.60 
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Example 7-1. Methodology Rank 3 for Wastewater 

A refinery has the following processing and production rates. The average annual emissions of 

hexane, benzene, toluene, and xylene can be estimated from the wastewater collection and treatment 

system for a BWON-compliant refinery. 

Process Unit or Operation Average Throughput (bbl/cd) 

Atmospheric distillation 100,000 

Vacuum distillation 50,000 

Catalytic reforming 20,000 

Catalytic cracking 40,000 

Alkylation 10,000 

Product blending 60,000 

Total crude and product tank throughput 180,000 

Use the factors in Table 7-8 and the density of water (ρwater = 8.34 lb/gal) to estimate the total 

wastewater flow rate and benzene loading rate. 

Process Unit 

or Operation 

(A) 

Average 

Throughput 

(bbl/cd) 

(B) 

Wastewater 

Flow Factor 

(gal/bbl) 

(C) = A×B 

Wastewater 

Flow 

(gal/cd) 

(D) 

Benzene 

Concentration 

(ppmw) 

(E) = C×ρ×D/106 

Benzene Mass 

Flow (lb/cd) 

Atmospheric 

distillation 

100,000 2.9 290,000 21 50.8 

Vacuum 

distillation 

50,000 3 150,000 12 15.0 

Catalytic 

reforming 

20,000 1.5 30,000 106 26.5 

Catalytic 

cracking 

40,000 2.4 96,000 13 10.4 

Alkylation 10,000 6 60,000 3 1.5 

Product 

blending 

60,000 2.9 174,000 24 34.8 

Tank 

drawdown 

180,000 0.02 3,600 188 5.6 

Totals 803,600 144.7 

Use the factors in Table 7-9 to estimate the mass loading rate of other compounds and the 

BWON-compliant emission factors in Table 7-10 to estimate the annual emissions. 

Compound 

(A) 

Mass Ratio from 

Table 7-9 

(B) = A×144.7 

Mass Flow (lb/cd) 

(C) 

Emission Factor 

from Table 7-10 

(D) = B×C×365/2000

Annual Emissions 

(tons/yr) 

Hexane 3.5 506.5 0.55 51 

Benzene 1.0 144.7 0.25 6.6 

Toluene 3.34 483.3 0.19 17 

Xylene 3.57 516.6 0.21 20 
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8. Cooling Towers 

Cooling water is used in refineries in heat exchange systems and condensers to cool or condense various 

product streams. The cooling water for a closed-loop recirculation system may be sent to a cooling tower, 

where it is cooled to near ambient temperature for reuse, and then is returned to the process or to 

refrigeration units for additional cooling. The cooling water for a once-through system may be cooled and 

sent to a receiving waterbody. This section focuses on cooling towers because these are used 

predominately in the petroleum refining industry. Some refineries use once-through cooling systems 

(emission estimates for once-through cooling systems can be estimated using essentially the same 

techniques used for cooling towers). 

Organic HAP and VOC are picked up by cooling water when leaks occur in heat exchangers or 

condensers. Product on the high-pressure side leaks through cracks in the exchanger and contaminates the 

water. Organic HAP, VOC, PM10, and chlorine are subsequently emitted from the water into the 

atmosphere due to stripping (i.e., active air and water contact) in the cooling tower and drift loss. Large 

emissions on the order of tons per year can occur for low levels of contamination or concentration 

because refineries use large volumes of cooling water. Generally, CH4 or other GHGs are not significant 

pollutants for cooling towers; however, if the cooling water is used on a high CH4 process stream, then 

CH4 emissions can be calculated using the same methods presented in this section for calculating volatile 

hydrocarbon emissions from cooling towers. The cooling tower emission estimates require information on 

the cooling water flow rate and the composition of the process stream in the heat exchanger or in the 

condenser or refrigeration units. These emission estimates are also dependent on the type of heat 

exchange monitoring system used. 

Table 8-1 summarizes the hierarchy of cooling tower emission estimation techniques. The methods are 

ranked in terms of anticipated reliability. Within a given measurement method (or rank), there may be 

alternative methods for determining the constituent-specific emissions; these compositional analysis 

methods are also provided in order of reliability. Multiple methods are provided for volatile organic HAP 

and VOC, while one method is provided for PM10, chlorine, and heavy organic HAP. Cooling towers may 

service more than one process and have multiple cooling water return lines. The monitoring performed 

on different cooling water return lines may differ for return lines leading to a single cooling tower. The 

methods described in this section can be applied to individual return lines (if the flow rate of each line is 

known) so that the total emissions from a cooling tower may be calculated as the sum of the emissions 

estimated for each return line. Different return lines to a single cooling tower may use different rank 

methodologies based on difference in the monitoring conducted on the individual return lines. 

The remainder of this section provides additional detail and guidance regarding the implementation of 

these methods. In general, annual emissions from cooling towers should account for the full operating 

time of the cooling tower on an annual basis. Annual cooling tower emissions can be estimated using the 

measured concentrations for each monitoring period (whether the measured concentration constitutes a 

leak or not) and summing emissions over all monitoring periods or can be estimated using emission 

factors for the full annual operating time of the cooling tower. Hourly emissions should be estimated 

based on the highest hourly emission rate for the cooling tower; when default emission factors are used, 

the hourly emissions should be determined based on the highest recirculation rate experienced for that 

year. 
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Table 8-1. Summary of Cooling Tower Emissions Estimation Methodologies 

Rank Measurement Method or Emission Factor Compositional Analysis Data 

1  Air stripping simulation using Appendix P, 

Modified El Paso method (speciated VOC) a

 Water recirculation rate 

 Speciation of collected gas samples with EPA TO14 or TO-15 methods, with EPA Method 18, or 

with a portable (not handheld) gas 

chromatograph/flame ionization detector 

2  Air stripping simulation using Appendix P, 

Modified El Paso methoda

, using a flame 

ionization detection analyzer (total VOC) 

 Water recirculation rate 

 Process-specific, service-specific concentrations 

 Process-specific average concentrations 

 Site-specific refinery average stream 

concentrations 

 Default process compositions 

3  Direct water measurement by EPA Method 

8260Bb

 before and after exposure to the 

atmosphere (e.g., at the cooling tower return 

line and at the outlet of cooling tower) 

 Water recirculation rate 

 Speciation of collected water samples 

4  Direct water measurement by EPA Method 

8260Bb

 before exposure to the atmosphere 

(e.g., at the heat exchanger exit line, or at the 

cooling tower return line) 

 Water recirculation rate 

 Speciation of collected water samples 

5  AP-42 emission factor for VOC, PM10, and 

chlorine 

 Water recirculation rate 

OR 

 Material balance 

 Process-specific, service-specific concentrations 

 Process-specific average concentrations 

 Site-specific refinery average stream 

concentrations 

 Default process compositions 

a

 Source: TCEQ, 2003. 

b

 Source: U.S. EPA, 1996. 

8.1 Methodology Ranks 1 and 2 for Cooling Towers 

The El Paso method (TCEQ, 2003) uses a flow-through system for air stripping a sample of water and 

analyzing the stripped gases for VOC using a flame ionization detection (FID) analyzer. This method 

measures the quantity of easily strippable components from the cooling water that have boiling points 

below 140°F. In this method, a continuous stream of cooling water is transferred via a pipe or flexible 

tubing to an air-stripping column apparatus. Air flowing countercurrent to the cooling water in the 

apparatus strips VOC and organic HAP from the water. Concentrations of pollutants in the air exiting the 

stripping column are measured, along with the air and water flow rates to the apparatus, to allow 

estimation of the concentrations of strippable VOC in the cooling water. At the apparatus air outlet, the 

concentrations may be measured using an on-site FID analyzer to determine the total strippable VOC 

(Methodology Rank 2 for cooling towers) or an on-site portable gas chromatograph (GC); (Methodology 

Rank 1 for cooling towers), or the concentrations may be measured by collecting samples in sample 

canisters for off-site laboratory analysis for speciation of air contaminants (Compendium Method TO14A, Compendium Method TO-15, or Method 18 [which are all Rank 1 methods]). 

The data necessary to implement Methodology Ranks 1 and 2 for cooling towers include speciated airstripped compounds concentration, operating parameters of the air-stripping apparatus, and the cooling 

water flow rate. Table 8-2 summarizes the data requirements for Methodology Ranks 1 and 2. 
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Table 8-2. Data Requirements for VOC or Speciated VOC Emissions, Methodology Ranks 1 and 2 

Rank Data That Must Be Collected The Way in Which Data Are Obtained 

Rank 1—

speciated VOC 

emissions 

 Speciated air-strippable VOC concentration 

measured in the stripped air (ppmv) 

 Periodic Appendix P testing results using 

an air-stripping column apparatus, followed 

by TO-14A, TO-15, EPA Method 18, or 

GC/FID 

 Sample water flow rate of the apparatus, 

stripping air flow rate of the apparatus, 

pressure in the air-stripping column 

apparatus chamber, and the temperature of 

stripping chamber 

 Measurements during Appendix P testing 

 Cooling water flow recirculation rates 

(gal/min) 

 Continuous measurements from pump flow 

rate curves, rotameters, or similar methods 

 Length of time of the monitoring period 

(hours) 

 Assume the measured concentration has 

occurred for half of the time period since 

the last sampling date; if a leak occurs, 

then add the time period it takes to repair 

the leak 

Rank 2—VOC 

emissions  Air strippable VOC concentration measured 

in the stripped air (ppmv) 

 Periodic Appendix P testing results using 

an air stripping column apparatus, followed 

by FID 

 Sample water flow rate of the apparatus, 

stripping air flow rate of the apparatus, 

pressure in the air-stripping column 

apparatus chamber, and temperature of 

stripping chamber 

 Measurements during Appendix P testing 

 Cooling water flow recirculation rates 

(gal/min) 

 Continuous measurements from pump flow 

rate curves, rotameters, or similar methods 

 Length of time of the monitoring period 

(hours) 

 From dates of monitoring events 

For cooling towers servicing process streams with multiple components, it is best to determine speciated 

compounds for air-strippable compounds from the cooling water. For cooling towers servicing process 

streams with single components, using the FID analyzer is likely adequate. Equation 8-1 should be used 

to calculate the concentration of the air-strippable components in the cooling water from the concentration 

detected in the stripped air outlet: 

samplewaterflow Water

Air i stripairflow

Water i R T a

C MW P PC b

C

*( 273) * * ρ

, * * * *

, + = (Eq. 8-1) 

where: 

 CWater,i = Concentration of air strippable compound “i” in the water matrix (parts per million by 

weight [ppmw]) 

 CAir,i = Concentration of compound “i” in the stripped air (parts per million by volume [ppmv]) 

 MW = Molecular weight of the compound (grams per mole [g/mol]) 

 P = Pressure in the air-stripping column apparatus chamber (inches [in.] of Hg) 

 PC = Pressure conversion factor (0.03342 atmospheres per inch [atm/in.] of Hg) 

 bstripairflow = Stripping air flow rate of apparatus (milliliters per minute [mL/min]) 

 R = Universal gas constant (82.054 milliliters-atmospheres per mole-Kelvin [mL-atm/mol-K]) 

 T = Stripping chamber temperature (°C) 
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asamplewaterflow = Sample water flow rate of apparatus (mL/min) 

ρWater= Density of the sample cooling water (g/mL). 

When using the El Paso method (TCEQ, 2003), the calculated concentration of the compounds in the 

water matrix represents the concentration that was stripped and does not represent the total concentration 

of the compounds in the water matrix prior to stripping. As such, this calculated water concentration is 

referred to as the “strippable pollutant concentration” in the cooling water. In general, when estimating 

the total VOC based on the FID analyzer, use the molecular weight (MW) of the calibration gas. 

Typically, CH4 is used for the calibration, so the MW for CH4 (16 g/mol) would be used to estimate the 

total VOC concentration in the water and the emission rate (reported “as CH4”). Even when a different 

calibration gas is used, one may need to use the MW for CH4 in the event a leak threshold is defined in 

units of ppmw or ppmv as CH4. 

In general, when the process stream is a single component, then the concentration on a CH4 basis from the 

FID can be converted to specific compounds that are expected to be leaking by accounting for C. For a 

multi-component process stream, it is better to determine speciated compounds using a portable GC/FID, 

TO-14A, TO-15, or Method 18. For portable GC results, in addition to calibration with a standard 

compound (CH4 or propane), the response factor of the unit should be determined for typical compounds 

expected in the air-stripped stream. For speciated compound results from an off-site laboratory, the 

concentration in the water for specific compounds can be estimated using the MW for the respective 

compound (e.g., benzene MW is 78 g/mol). These speciated concentrations (calculated using the 

compound-specific MW) should be used when estimating emissions for the purposes of an emissions 

inventory. However, it is important to note that for specific regulatory purposes, these concentrations 

must be converted to a CH4 basis (using the MW of CH4) for comparison to a leak definition threshold 

that is on an “as CH4” basis, as shown below in Example 8-1. 

Example 8-1: How to Compare Speciated Concentration Results with Leak Definitions 

That Are Defined as Methane 

A facility conducts El Paso monitoring that provides speciated results, but, for regulatory 

purposes, these concentrations must be converted to a CH4 basis for comparison to a leak 

definition for the stripping air that is on a CH4 basis. 

Given: Speciated El Paso monitoring found hexane concentration in the stripped air of 5 

ppmv. What is the concentration “as methane?” 

In this example, hexane concentration in the stripped air is 5 ppmv. The following equation 

should be used to convert this concentration to CH4 basis: 

4

4

6 14

6

6 14 30 ppmv as CH

1moleC

1moleCH *

1moleC H

6 moleC *

10 mole air

5 mole C H

5 ppmv Hexane =⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛ =

If the leak definition is 6.2 ppmv as CH4, then a leak has been detected because the hexane 

concentration is equivalent to 30 ppmv as CH4. 
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Equation 8-2 should be used to estimate emissions for air strippable total VOC from the cooling water: 

2000 lb

1 ton

gal

lb 8.34

hr

min 60

10 ppm 6

, = × CoolingWater × × × Year ×

Water i

i Flow H

C

E (Eq. 8-2) 

where: 

 Ei = Emissions of air strippable pollutant “i” from the cooling water (tons) 

FlowCoolingWater = Flow rate of cooling water (gallons per minute [gal/min]) 

 60 = Unit conversion for minutes per year (min/yr) 

 8.34 = Density of water in pounds per gallon (lb/gal) 

 1/2000 = Unit conversion for tons per pound (tons/lb) 

 HYear = Length of time of the monitoring period or the length of time a leak occurs (hr) 

When Cair,i is based on total VOC results from an FID analyzer (Methodology Rank 2 for cooling towers), 

pollutant “i” is simply VOC. 

When Cair,i is based on GC analysis results for individual species (Methodology Rank 1 for cooling 

towers) or based on site-specific or default species composition data (Methodology Rank 2 for cooling 

towers), pollutant “i” will be the individual pollutant. 

If monitoring or sampling events occur regularly or periodically (i.e., quarterly or monthly), then 

concentration measurements for consecutive monitoring events can be used to estimate the average 

emission rate during the intervening period by assigning each concentration measurement to half of the 

time period between monitoring/sampling events. If significant concentrations of organics are detected in 

the cooling water (i.e., a “leak” is detected), then the measured concentration is also attributed to the time 

span from when the leak was discovered until the time when it was repaired. This method is analogous to 

the “midpoint” method used to annualize equipment leak emissions when periodic monitoring is used. As 

with equipment leaks, the “modified trapezoid” or “average period” methods could also be used to 

annualize emissions from cooling towers when periodic monitoring of the cooling water is performed (see 

Section 2.2.2, Calculating Annual Average Equipment Leak Emissions, in this Refinery Emissions 

Protocol for additional details). 

When monitoring or sampling is not conducted regularly or periodically, any measured concentration 

should be used to calculate the average emission rate from the cooling tower, assuming the concentration 

is constant for the entire year. In this situation, if the concentration measurement suggests a leak that is 

subsequently repaired, then use the initially determined “leak” concentration for the entire reporting year 

up to the time when the leak was repaired. 
Version 2.1.1 

Final ICR Version – Corrected Section 8—Cooling Towers 

8-6 

Example 8-2: Calculation for Methodology Rank 1 for Cooling Towers 

Given: A cooling tower with a water recirculation rate of 32,000 gal/min is monitored 

quarterly using speciated El Paso monitoring. A hexane concentration in the stripped air of 5.0 

ppmv is detected during the second quarterly monitoring event, indicating a “leak.” The 

properties of the El Paso stripping column during this monitoring event were as follows: 

pressure =29.9 in. of Hg; strippable air flow in the apparatus = 2,500 mL/min; temperature = 

32°C; sample water flow rate in the apparatus = 125 mL/min. The leak repair took 45 days 

from the monitoring event to complete. Assuming all other monitoring events found no 

detectible concentrations of hexane, what are the annual emissions of hexane? 

Solution: First use Equation 8-1 to calculate the concentration of air strippable compound in 

the water as follows.

ppmw Hexane

ml

ml g

mole K

ml atm

ml

in Hg

atm in Hg moleg ppmv

C WaterSpeci es 0 .34

* 1

min

82 .054 * (32 273 ) * 125

min * 2500 . 5 .0 * 86 .17 * 29 .9 . * 0 .03342

=

+ −

− =

Thus, the 5 ppmv hexane concentration in the air stream translates to 0.34 ppmw “strippable” 

hexane in the cooling water. 

Next, the emissions must be estimated for the period between the first and second quarterly 

monitoring events. The exact timing of the monitoring events should be recorded and used, 

but from the information given (quarterly monitoring), we assume the monitoring events 

occur 91 days (2,184 hours) apart. One can use either the midpoint, modified trapezoid, or 

average period emission rate. Using the modified trapezoid or average period method and 

noting the effective water concentration of the first monitoring event is 0 ppmv hexane, the 

emissions between the first and second monitoring event is: 

( ) 2.97 ton Hexane

2000lb

1ton * 2,184 hr *

gal

lb *8.34

hr

min *60

min

gal *32,000

10

0.34 0 2 ,1 6 = − Ei =

Similarly, the emissions for the period from the second quarterly monitoring event and the 

leak repair is estimated. This period is given as 45 days (or 1,080 hours). 

2.94 ton Hexane

2000lb

1ton *1,080 hr *

gal

lb *8.34

hr

min *60

min

gal *32,000

10

0.34 ,2 6 Ei = =

As these are the only measurable emissions for the year, the annual emissions would be 

calculated as Ei = Ei,1 + Ei,2 = 2.97+2.94 = 5.91 tons, which is 5.9 tons when rounded to two 

significant figures. 

Note: The advantage of the midpoint method is that it uses the same leak concentration for the 

period between the leak being detected and repaired as the “half” period prior to the 

monitoring event. Consequently, the time period from the monitoring event and leak repair 

can be added to the “half” period prior to the monitoring event (91 days÷2 = 1,092 hrs) to 

calculate a total duration of the leak and calculate the cumulative emissions in one step as 

follows: 

( ) 5.9 ton Hexane

2000lb

1ton * 1,092 1,080 hr *

gal

lb *8.34

hr

min *60

min

gal *32,000

10

0.34

6 Ei = + =
Version 2.1.1 

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8-7 

Example 8-3: Calculation for VOC Emissions Using Methodology Rank 2 for Cooling 

Towers 

Given: The cooling tower with a water recirculation rate of 25,000 gal/min is monitored 

quarterly using El Paso stripping column (same stripping column properties as in Example 

8-2) and a VOC concentration in the stripped air of 14 ppmv (as CH4) is measured on 

February 1, 2009. The leak was repaired on March 4, 2009 (31 days later). All previous and 

subsequent monitoring events found VOC concentration in the stripped air of 1 ppmv. What 

is the annual emissions of VOC from this cooling tower in 2009? If the process fluid contains 

10 wt% benzene and a total light (strippable) organic content of 80%, what is the annual 

emissions of benzene from this cooling tower in 2009? 

Solution: Equation 8-1 is used to calculate the concentration of air strippable VOC in the 

water as CH4. The water concentration corresponding to the stripping air concentration of 14 

ppmv is: 

, CH4 0.179ppmwVOCas

*1

min

82.054 *(32 273) *125

min

*2500 . 14 *16.04 *29.9 . *0.03342

=

+ −

− =

ml

ml g

mole K

ml atm

ml

in Hg

atm in Hg mole

g ppmv

CWaterVOC

In the same manner, the water concentration corresponding to the stripping air concentration 

of 1 ppmv is: 0.0128 ppmw as CH4 (0.179/14). 

Because the leak was identified during the first quarterly monitoring event, the method used to 

estimate emissions between monitoring intervals (i.e., the midpoint, modified trapezoid, or 

average period method) will yield slightly different results for 2009, although the total 

emissions across both 2008 and 2009 will be identical. The modified trapezoid method is the 

most complicated, requiring interpolation to determine the effective leak rate on January 1, 

2009, before the emissions between Januaruy 1 and February 1 can be calculated. We 

generally recommend the midpoint method due to its ease of use, but the same method should 

be used for all cooling towers and all inventory years. 

Using the midpoint method, the water concentration of 0.179 ppmw as CH4 is present for 62 

days (or 1,488 hour) in 2009 (from Jan. 1 to March 4, 2009). The emissions during this period 

are: 

1.67 ton VOC

2000

1 *8.34 *1,488 * min *60

min

* 25,000

10

0.179 ,1 6 = = lb

ton hr

gal

lb

hr

gal EVOC

For the remainder of the year (8760 – 1488 = 7,272 hrs), the emissions are: 

0.58 ton VOC

2000

1 *8.34 *7,272 * min *60

min

* 25,000

10

0.0128 ,2 6 = = lb

ton hr

gal

lb

hr

gal EVOC

Therefore, the 2009 VOC emissions from this cooling tower are 1.67 + 0.58 = 2.25 tons VOC. 
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8-8 

8.2 Methodology Rank 3 for Cooling Towers 

Methodology Rank 3 is used to estimate emissions from cooling towers and involves using a mass 

balance approach based on sampling the cooling water before and after the cooling tower. Although 

Methodology Rank 3 has the potential to be as appropriately reliable as Methodology Ranks 1 or 2 for 

large leakers, Rank 3 suffers from detection limit issues with water sampling techniques. Consequently, 

this monitoring approach will not detect the smaller leaks that could significantly contribute to VOC or 

HAP emissions. 

Cooling water typically has low concentrations of components and large volumes of flow rate, so direct 

water sampling typically requires analysis for low-level concentrations. A common method used for 

cooling water sampling is Method 8260B. In this method, the sample is introduced into a gas 

chromatography/mass spectrometry (GC/MS) system, the GC column is temperature programmed to 

separate the components, and the components are detected with MS. The results from the method are the 

concentrations of components in the cooling water. Typically, two cooling water samples are taken to 

estimate the emissions: one sample before and one sample after the cooling water has been exposed to the 

atmosphere. The change in the component concentration of the cooling water multiplied by the cooling 

water recirculation rate provides the quantity emitted into the atmosphere for the duration of the leak. 

The data necessary to implement Methodology Rank 3 for cooling towers include speciated compounds 

concentration in the cooling water and the cooling water flow rate. Table 8-3 summarizes the data 

requirements of Methodology Rank 3. 

Example 8-4: Calculation for Speciated HAP Emissions using Methodology Rank 2 for 

Cooling Towers 

Given: The cooling tower in Example 8-3 serves a process unit whose process fluid contains 

10 wt% benzene and a total light (strippable) organic content of 80%. What is the annual 

emissions of benzene from this cooling tower in 2009? 

Solution: In Example 8-3, theVOC emissions were calculated to be 2.25 tons in 2009. To 

determine the mass emissions of benzene, the mass of benzene per mass of VOC stripped in 

the El Paso column must be calculated. In this example, 80 percent of the process fluid is 

expected to be strippable organics. The remaining 20 percent may be either inorganic 

compounds, like H2 or N2 that are stripped but are not detected by the organic analyzer, or 

heavier organics that do not strip appreciably in the stripping column. While more detailed 

calculations could be performed for compounds that may marginally strip, for the purposes of 

speciating volatile emissions, it is assumed these non-volatile compounds are not stripped. 

Benzene represents 10% of the total mass of fluid leaking into the cooling water. Since the 

total strippable organic content of fluid leaking into the cooling water is 80 percent, the mass 

fraction of benzene per mass of strippable VOC is 0.1/0.8 or 0.125. 

Therefore, benzene is expected to contribute 12.5 percent of the total strippable VOC 

concentration or 0.28 tons benzene (0.125 tons benzene per ton VOC × 2.25 tons VOC). 
Version 2.1.1 

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8-9 

Table 8-3. Data Requirements for Speciated Compound Emissions, Methodology Rank 3 

Rank Data That Must Be Collected The Way in Which Data Are Obtained 

Rank 3—

speciated 

emissions 

 Speciated compounds concentration 

measured in the inlet cooling tower return 

line (ppmw) 

 Periodic sampling results using Method 8260B, 

including a measurement prior to exposure to the 

atmosphere 

 Speciated compounds concentration 

measured in the outlet cooling water 

(ppmw) 

 Periodic sampling results using Method 8260B, 

including a measurement after exposure to the 

atmosphere 

 Cooling water flow recirculation rates 

(gal/min) 

 Continuous measurements from pump flow rate 

curves, rotameters, or similar methods 

 Length of time of the monitoring period 

(hours) 

 Assume the measured concentration has 

occurred for half of the time period since the last 

sampling date; if a leak occurs, then add the time 

period it takes to repair the leak 

The change in the component concentration in the cooling water before and after being exposed to the 

atmosphere is used, along with the cooling water recirculation rate, to estimate the emissions from the 

cooling water. The following equation (Equation 8-3) can be used to calculate the emissions of 

components from the cooling water. It is important to note that it is assumed that the water make-up rates 

offset any drift loss and blowdown loss; therefore, flow “in” to a cooling tower is the same as flow “out” 

and can be determined based on the water recirculation flow rate, regardless of where this measurement 

takes place. 

( )

2000 lb

1 ton

hr

min 60

gal

lb 8.34

106

, , × × × × × − = CoolingWater Year

i In i Out

i Flow H

C C

E (Eq. 8-3) 

where: 

 Ci,In = Concentration of component “i” in the cooling water prior to exposure to the 

atmosphere (ppmw) 

 Ci,Out = Concentration of component “i” in the cooling water after exposure to the atmosphere 

(ppmw) 

As shown in Equation 8-4, the total emissions from the cooling water are the sum of all component 

species emitted and can be summed specifically for VOC or organic HAP: 

∑=

=

n

i

ETotal Ei

1

 (Eq. 8-4) 
Version 2.1.1 

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8-10 

8.3 Methodology Rank 4 for Cooling Towers 

Methodology Rank 4, similar to Methodology Rank 3, uses direct cooling water samples for analysis of 

VOC and HAP contained in the cooling water, and a water sample is taken and sent for laboratory 

analysis. Under Methodology Rank 4 for cooling towers, only one sample is taken of the cooling water 

prior to being exposed to the atmosphere to estimate emissions. In this method, it is assumed that 100% of 

the compound is emitted at the cooling tower. As such, this methodology will likely overestimate the 

cooling water emissions, and would be a conservative (i.e., resulting in greatest emissions) estimate. 

The data necessary to implement Methodology Rank 4 for cooling towers include speciated compounds 

concentration in the cooling water and the cooling water flow rate. Table 8-4 summarizes the data 

requirements of Methodology Rank 4. 

Example 8-5: Calculation for Methodology Rank 3 for Cooling Towers 

Given: Concentrations for total xylenes in the cooling water are determined semi-annually. 

During the first measurement event the concentration of xylene in the cooling water return 

line before exposure to the atmosphere was 0.220 ppmw and 0.080 ppmw in the cooling water 

flow to the heat exchanger after exposure to the atmosphere. Sampling during the second 

monitoring event showed xylene concentrations of 0.320 ppmw before and 0.100 ppmw after 

exposure to the atmosphere in the cooling tower. The cooling water recirculation rate averages 

55,000 gal/min with a maximum recirculation rate of 65,000 gal/min. The cooling tower 

operated for 8,000 hours during the year. What are the annual and maximum hourly 

emissions of xylene from the cooling tower? 

Solution: For monitoring that occurs semi-annually or less often attributing the emissions 

between monitoring events and the calendar year can be cumbersome. As no leak repair was 

conducted, it can be assumed that these two measurement are equally representative for the 

year. The average hourly emission rate of xylene is calculated using Equation 8-3 for each of 

the monitoring events as follows: 

( ) 3.85lb/hr

hr

min 60

gal

lb 8.34

min

gal 55,000

10

0.22 0.08 ,1 6

× × × = − Ei =

( ) 6.05lb/hr

hr

min 60

gal

lb 8.34

min

gal 55,000

10

0.32 0.10 ,2 6

× × × = − Ei =

The average hourly emissions rate during the year can be calculated as the arithmetic average 

of these two hourly estimates, which is 4.95 lb/hr [(3.85+6.05)/2]. The annual emissions are 

then calculated based on the operating hours as: 4.95 lb/hr × 8,000 hours × 1 ton/2,000 lbs = 

19.8 tons of xylene. 

The maximum hourly emissions of xylene are calculated using they highest net measurement 

concentration and the maximum recirculation rate as follows. 

( ) 7.16lb/hr

hr

min 60

gal

lb 8.34

min

gal 65,000

10

0.32 0.10 ,max 6

× × × = − Ei =
Version 2.1.1 

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8-11 

Table 8-4. Data Requirements for Speciated Compound Emissions, Methodology Rank 4 

Rank Data That Must Be Collected The Way in Which Data Are Obtained 

Rank 4—

speciated 

emissions 

 Speciated compounds concentration 

measured in the inlet cooling tower return 

line (ppmw) 

 Periodic sampling results using Method 

8260B, including a measurement prior to 

exposure to the atmosphere 

 Cooling water flow recirculation rates 

(gal/min) 

 Continuous measurements from pump 

flow rate curves, rotameters, or similar 

methods 

 Length of time of the monitoring period 

(hours) 

 Assume the measured concentration has 

occurred for half of the time period since 

the last sampling date; if a leak occurs, 

then add the time period it takes to repair 

the leak 

The component concentration in the cooling water before being exposed to the atmosphere is used with 

the cooling water flow rate to estimate the emissions from the cooling water. The following equation 

(Equation 8-5) should be used to calculate the emissions of components from the cooling water: 

( )

2000lb

1ton

hr

min 60

gal

lb 8.34

106

, = × CoolingWater × × × Year ×i In

i Flow H

C

E (Eq. 8-5) 

where: 

 Ci,In = Concentration of component “i” in the cooling water prior to exposure to the 

atmosphere (ppmw) 

Equation 8-5 is equivalent to Equation 8-3 with Ci,Out set equal to zero. Thus, the calculations performed 

for Methodology Rank 4 for cooling towers is essentially identical to those for Methodology Rank 3 for 

cooling towers. Equation 8-4 can be used to calculate the total VOC or total organic HAP emissions from 

the cooling water. 

8.4 Methodology Rank 5 for Cooling Towers 

Methodology Rank 5 for cooling towers uses emission factors from AP-42 (U.S. EPA, 1995a; Sections 

5.1 and 13.4). The AP-42 emission factors approved for use in Methodology Rank 5 for cooling towers 

are summarized in Table 8-5. The remainder of this section describes the use of these emission factors 

for different classes of pollutants. 

Table 8-5. Methodology Rank 5 Default Emission Factors 

Type of Cooling Tower 

VOC Emission Factor 

(lbs/MMgal) a Drift Factor (lbs/MMgal) a PM10 Emission Factor (lbs/MMgal) b

Induced draft, counter flow 6.0 1,700 31.5 

Induced draft, cross flow 6.0 1,700 40.8 

Unspecified draft or flow type 6.0 1,700 35.0 

Natural draft 6.0 73 No data 

a

 Source: U.S. EPA, 1995a; presented in units of pounds per million gallons (lb/MMgal) of recirculation. b

 Source: U.S. EPA, 1995a; calculated as the product of the drift factor from Table 13.4-1 and the total dissolved 

solids concentration in Table 13.4-2. 
Version 2.1.1 

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8-12 

8.4.1 VOC and Volatile Organic HAP 

Methodology Rank 5 for volatile organics from cooling towers uses the uncontrolled VOC emission 

factor given in AP-42 (U.S. EPA, 1995a; Section 5.1) of 6 pounds of total VOC per million gallons of 

water (MM gal) (equivalent to a concentration in the water of 0.7 ppmw). The controlled emission factor 

provided in AP-42 should not be used. The controlled emission factor only applies to refineries that 

directly monitor for hydrocarbons (and organic HAP) and repair leaks when they occur, in which case the 

refineries would have monitoring data to conduct emission estimates under Methodology Ranks 1, 2, 3, or 

4 for cooling towers. 

To estimate HAP emissions, refineries should use site-specific information on the composition of process 

streams cooled in heat exchangers and condensers if available. Process-specific concentrations, processspecific average concentrations, or site-specific refinery average stream concentrations should be used 

when available. If these data are not available, then the default average refinery process stream 

compositions given in Appendix A, Average Stream Compositions, Table A-1, may be used to speciate 

the VOC and generate HAP emissions estimates. 

The data necessary to implement the Methodology Rank 5 for cooling towers include the AP-42 

uncontrolled VOC emission factor, the cooling water flow rate, and the process stream composition. 

Table 8-6 summarizes the data requirements of Methodology Rank 5. 

Table 8-6. Data Requirements for VOC or Speciated VOC Emissions, Methodology Rank 5 

Rank Data That Must Be Collected The Way in Which Data Are Obtained 

Rank 5—estimated 

speciated 

emissions 

 AP-42 uncontrolled emission factor for 

cooling towers of 6 pounds of VOC per 

million gallons of water 

 Not applicable 

 Process stream composition data  Measurement/sampling of process stream 

composition, engineering knowledge of 

process composition, or default average 

composition for the industry 

 Cooling water flow recirculation rates 

(gal/min) 

 Continuous measurements from pump 

flow rate curves, rotameters, or similar 

methods 

 Operating hours (hours)  Use operating hours of cooling tower or 

assume continuous operation (8,760 

hr/yr, non-leap year) 

The following equation (Equation 8-6) should be used to estimate VOC emissions: 

2000 lb

1 ton

hr

min EVOC = EFUnc × FlowCoolingWater × 60 × HYear × (Eq. 8-6) 

where: 

 EFUnc = Uncontrolled emission factor for cooling towers from AP-42 (Section 5.1) 

 = 6.0 pounds of VOC per 106

 gallons of cooling water (lb/MMgal). 

The following equation (Equation 8-7) should be used to estimate the emissions for a particular species 

component: 

2000lb

1ton

hr

min Ei = EFUnc ×WtFraci × FlowCoolingWater × 60 × HYear × (Eq. 8-7) 
Version 2.1.1 

Final ICR Version – Corrected Section 8—Cooling Towers 

8-13 

where: 

 WtFraci = Approximate weight fraction of component i in the cooling water 

8.4.2 Particulate Matter Emissions 

Methodology Rank 5 for cooling towers uses the total liquid drift emission factors given in AP-42 (U.S. 

EPA, 1995a; Section 13.4), which are also provided for convenience in Table 5-5, and the total dissolved 

solids (TDS) weight fraction to estimate PM10 emissions. It is conservatively assumed that all TDS are in 

the PM10 size range. 

Site-specific TDS concentration in the cooling water should be used when available (Methodology Rank 

5A for PM from cooling towers). When direct TDS monitoring is not conducted, AP-42 (U.S. EPA, 

1995a) recommends that the TDS be estimated from TDS concentration of the makeup water times the 

“cycles of concentration ratio” of a monitored parameter (Methodology Rank 5B for PM from cooling 

towers). The cycles of concentration ratio is the concentration of a monitored parameter (such as 

conductivity, calcium, chlorides, or phosphate) in the cooling tower recirculating water divided by the 

concentration of that measured parameter in the makeup water. Alternatively, Methodology Rank 5B for 

PM from cooling towers can use a direct correlationof a monitored parameter to TDS concentration. For 

Example 8-6: Calculation for Methodology Rank 5 for Cooling Towers 

Given: An unmonitored cooling tower with a water recirculation rate of 25,000 gal/min is 

servicing a heat exchanger cooling a reformulated gasoline stream. Estimate the annual VOC 

and HAP emissions from this cooling tower. 

Solution: Equation 8-6 should be used to calculate the annual emissions of VOC, EVOC: 

39.4 ton VOC

2000lb

1ton 8,760

hr

min 60

min

gal 25,000

10 gal

6 lbVOC

6 EVOC = × × × hr × =

Without site-specific stream composition, use the default concentrations for reformulated 

gasoline in Appendix A, Average Stream Compositions, and use Equation 8-7 to estimate the 

emissions for each HAP component in the gasoline stream. For example, to calculate the 

annual emissions of benzene, the liquid composition for benzene is 0.7 wt%. Using this 

concentration in Equation 8-7 yields: 

0.28 ton Benzene

2000lb

1ton 8,760

hr

min 60

min

gal 0.007 25,000

10 gal

6 lbVOC

6 Ei = × × × × hr × =

Similarly, emissions of other consistuents are estimated as follows: 

 Cumene of 0.19% by weight; emissions are 0.075 ton 

 Ethylbenzene of 1.26% by weight; emissions are 0.50 ton 

 Hexane of 1.36% by weight; emissions are 0.54 ton 

 Naphthalene of 0.21% by weight; emissions are 0.083 ton 

 Toluene of 7.0% by weight; emissions are 2.8 ton 

 2,2,4-Trimethylpentane of 1.1% by weight; emissions are 0.43 ton 

 Xylene of 7.3% by weight; emissions are 2.9 ton 

The total HAP emissions for this cooling tower are calculated by summing the emissions of 

the individual HAP; the total annual HAP emissions for this cooling tower are 7.6 tons. 
Version 2.1.1 

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8-14 

example, it is commonly suggested that the Equation 8-8 be used to estimate TDS concentration from 

conductivity measurements. 

TDS (ppmw) CF Conductivity (μ mho/cm)) = TDS × (Eq. 8-8) 

where: 

 TDS = Total dissolved solids concentration of the cooling water (ppmw) 

 Conductivity = Conductivity of cooling water (micromho per centimeter [μmho/cm]). 

 CFTDS = Correlation factor to convert conductivity to TDS concentration (ppmw per μmho/cm) 

 = 0.5 to 1.0; default is 0.67 (see http://www.appslabs.com.au/salinity.htm) 

The correlation factor is dependent on the specific electrolytes present and the total concentration of 

electrolytes. At low conductivity (<1,000 μmho/cm), CFTDS = 0.5. The correction factor increases with 

increasing TDS concentrations. A site-specific correction factor or curve should be used based on paired 

measurements over the range of typical measured conductivity values. Otherwise, the default correction 

factor of 0.67 should be used. 

Once the the TDS weight fraction is determented, the PM10 emissions corresponding to the TDS 

measurement value is calculated using Equation 8-9. 

2000lb

1ton

hr

min EPM10 = EFDrift ×WtFracTDS × FlowCoolingWater × 60 × H Period × (Eq. 8-9) 

where: 

 EPM10 = Emissions of PM10 during the measurement period (tons or tons per period) 

 WtFracTDS = Weight fraction of TDS (Note, 1,000 ppmw = 0.001 wt fraction) 

 HPeriod = Number of hours associated with the monitored TDS concentration (hrs). 

If no data are available to estimate TDS concentration in the cooling water, then the default average PM10

emission factors provided in Table 8-5 (which are based in the TDS fraction from AP-42, Table 13.4-2) 

should be used. These default PM10 emission factors represent Methodology Rank 5C for PM from 

cooling towers. Emissions of PM10 are calculated using Equation 8-10, which is essentially identical to 

the calculation for total VOC emissions. 

2000 lb

1 ton

hr

min EPM10 = EFPM10 × FlowCoolingWater × 60 × HYear × (Eq. 8-10) 

where: 

 EFPM10 = Default emission factor for PM10 from cooling towers from Table 8-5. 
Version 2.1.1 

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8-15 

Example 8-7: Calculation for Annual PM Emissions Using Methodology Rank 5B for 

PM from Cooling Towers 

Given: A cooling tower with a water recirculation rate of 25,000 gal/min is sampled monthly 

for TDS. What are the annual emissions of PM10? If the highest recirculation rate is 30,000 

gal/min, what is the maximum hourly PM10 emissions rate? 

Solution: Using the site-specific TDS fraction, the operating hours associated with each TDS 

concentration period can be determined using the midpoint method as shown in the following 

table (Column 3). Equation 8-9 is applied to each concentration period to calculate the 

emissions of PM10 for that period (Column 4). The sum of the emissions in Column 4 yields a 

total annual emissions of 22.7 tons (or 23 tons rounded to 2 significant digits). 

1 

Date 

2 

TDS Concentration 

(ppmw) 

3 

Hours Assigned to 

TDS Concentration 

4 

Emissions (tons for 

concentration period) 

Jan 10 (startup Jan 1) 360 240+300=540 0.25 

February 4 520 300+336=636 0.33 

March 4 780 336+372=708 0.70 

April 4 1,100 372+360=732 1.03 

May 4 1,260 360+372=732 1.18 

June 4 2,300 372+360=732 2.15 

July 4 3,500 360+372=732 3.27 

August 4 5,500 372+372=744 5.22 

September 4 4,600 372+360=732 4.29 

October 4 1,700 360+372=732 1.59 

November 4 2,100 372+624=996 2.67 

December (shutdown Dec 1 

- not operating in December) 

0 744 0.00 

Total 8,760 22.7 ton 

The maximum TDS concentration (5,500 ppmw) and the maximum cooling water recirculation 

rate of 30,000 gal/min is used in Equation 8-9 to calculate the maximum hourly PM10 emissions 

rate as follows: 

10 6 6 PM10 14 lbs/hr 

hr

min 60

min

gal 25,000

10 lb water

5,500 lb TDS

10 gal

1,700 lb drift EPM = × × × =
Version 2.1.1 

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8-16 

8.4.3 Non-volatile Organic HAP Emissions 

Organic compounds with low volatility, such as most POM compounds, will not be effectively stripped 

from the cooling water. These compounds will tend to accumulate in recirculated cooling water, and will 

primarily be released as drift from the cooling tower. The emissions of these compounds can be 

estimated from their concentration in the cooling water and the liquid drift factor in the same manner used 

to calculate PM10 emissions using Equation 8-9. 

8.4.4 Chlorine Emissions 

Site-specific material balance may be one method of estimating chlorine emissions. Otherwise, limited 

information is available regarding chlorine emission factors for cooling towers. EPA is currently 

reviewing available data to develop guidance for estimating chlorine emissions from cooling towers. To 

aid in developing that guidance, EPA is seeking additional data and suggestions for emission estimation 

methodologies. 

Example 8-8: Calculation Using Methodology Rank 5C for PM from Cooling Towers 

Given: A forced draft, cross-flow cooling tower with a water recirculation rate of 25,000 

gal/min in service all year. No TDS concentration data are available. What are the annual 

emissions of PM10 emissions? 

Solution: Since no TDS measurement data are available, use the default PM10 emission 

factors from Table 8-5. The appropriate emission factor for a forced draft, cross-flow 

cooling tower is 40.8 lb/MMgal. The cooling tower was operated all year (8760 hours). Using 

Equation 8-10, the annual emissions of PM10, EPM10, are calculated as follows: 

6 10

10

10 268 ton PM

2000 lb

1 ton 8,760 hr

hr

min 60

min

gal 25,000

10 gal

40.8 lb PM

EPM = × × × × =
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9. Loading Operations 

Product or commodity loading emissions occur when vapor is displaced by the product or commodity 

when it is loaded into tank trucks, rail cars, and marine vessels (which include both ships and barges). The 

vapor may contain constituents from the material previously transported and from the product currently 

being loaded. HAP, VOC, and GHG are emitted from loading operations. Emission from loading 

operations should be estimated for all materials loaded into tank trucks, rail cars, and marine vessels such 

as final products, intermediates, additives, or wastes. Loading operations also include loading materials 

into drums or containers, such as LPG container filling operations or loading waste into drums for off-site 

disposal. 

Loading emission estimates require information on the quantity of material loaded annually, the 

component composition of the material loaded and the vapor pressures of the components, the loading 

procedure, the type of vessel being loaded, and the effectiveness of the capture system and the controls 

used. Emissions from gasoline loading racks are regulated under the Petroleum Refinery MACT I (40 

CFR Part 63, Subpart CC) and are limited to 10 milligrams of TOCs per liter of gasoline (Subpart CC 

references Subpart R, which references some requirements for 40 CFR Part 60, Subpart XX). Emissions 

from marine vessel loading operations for crude, gasoline, and other products are also regulated under the 

Petroleum Refinery MACT I (Subpart CC references the Marine Vessel Loading MACT in 40 CFR Part 

63, Subpart Y) and are subject to a 97% emission-reduction requirement for existing sources and 98% 

emission-reduction requirement for new sources. 

Emissions from loading operations may be reduced by using submerged loading or bottom loading. 

Additionally, emissions from loading operations may be captured and controlled using a vapor collection 

system and an add-on air pollution control device. Vapor balancing may be used as an alternative to addon controls to reduce emissions from loading operations. If an add-on air pollution control device or a 

vapor balance system is used to capture and control emissions, then capture and control efficiencies 

should be included in the emission estimate. 

Control devices used for loading operations typically include thermal or catalytic incinerators, adsorption 

systems, scrubbers, and flares. Vapor balancing systems are allowed as an option or an alternative for 

marine vessel loading operations under Subpart CC of the Petroleum Refinery MACT I. For loading racks 

subject to gasoline loading requirements, typically an EPA Method 25A or 25B performance test is 

conducted on the control device to collect outlet TOC concentration data and determine an outlet 

emission factor based on the volume of gasoline loaded (i.e., meet the less than 10 milligrams of total 

hydrocarbon per liter gasoline loaded [mg/L]). For marine vessel loading subject to requirements under 

Subpart CC MACT I, typically, a Method 25 performance test is conducted on the control devices to 

collect inlet and outlet TOC concentration data and determine a control efficiency. 

Table 9-1 summarizes the hierarchy of loading operation emission estimation techniques. Within a given 

measurement method (or rank), there may be alternative methods for determining the constituent-specific 

emissions; these compositional analysis methods are also provided in order of accuracy. Methodology 

Ranks 1, 2, and 3 for loading operations only apply loading operations that are controlled; uncontrolled 

loading operations must estimate their emissions using Methodology Ranks 4 for loading operations. The 

remainder of this section provides additional details and guidance regarding the ways in which to 

implement these methods. 
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Table 9-1. Summary of Loading operations Emission Estimates 

Rank Measurement Method or Emission Factor Compositional Analysis Data 

1A Direct measurement (CEMS) for both flow rate 

and gas composition 

 Pressure, temperature, and moisture content 

(depending on the monitoring system) 

1B Direct measurement (CEMS) for both flow rate 

and THC 

 Process-specific, service-specific concentrations 

based on measurement data 

2 Direct measurement by EPA Method 18 (sitespecific emission factor) and loading rate 

 Not applicable 

3 Direct measurement by EPA Method 25, 

Method 25A, or Method 25B (site-specific 

emission factor) and loading rates 

 Process-specific, service-specific concentrations 

 Process-specific average concentrations 

 Site-specific refinery average stream concentrations 

 Default process compositions 

4 AP-42 emission factor (default emission 

factor) and loading rates 

 Process-specific, service-specific concentrations 

 Process-specific average concentrations 

 Site-specific refinery average stream concentrations 

 Default process compositions 

9.1 Data Available on Product Composition and Properties 

To speciate the emissions into VOC or HAP, facilities should use site-specific information on the 

composition of the material loaded if available (for more information, see Section 9.3.2, Estimate 

Controlled or Uncontrolled Emissions and Speciate). Data are often available on the product or 

commodity composition, sometimes for both the liquid and vapor phases and sometimes only for the 

liquid phase. Material-specific or site-specific concentrations should be used when available. If materialspecific or site-specific data are not available, then the default average compositions for refinery process 

and product streams presented in Table A-1 of Appendix A, Average Stream Compositions, may be used 

to speciate and generate VOC and HAP emission factors. 

Other properties such as the MW of the liquid, the MW of the vapor, and the vapor pressure of a 

multicomponent product or commodity are also often available. When these data are not readily available 

at the refinery, data from various references can be used or can be calculated using basic principles. For 

instance, property data are available in AP-42, Section 7.1 (Organic Liquid Storage Tanks), in Table 

7.1-2 for various petroleum fuels and in Table 7.1-3 for various petrochemicals (U.S. EPA, 1995a). 

If the weight composition of a commodity is available but other property data are not, estimates can be 

made. Appendix A presents equations that may be used for calculating estimates of the liquid vapor 

pressure, the molecular weight of the vapor, and the weight fraction of the vapor given a known liquid 

component composition. 

9.2 Methodology Rank 1 for Loading Operations 

For pollutants such as THC, it is anticipated that some loading operations may have CEMS for measuring 

the composition and the gas flow rate of the emissions from loading operations. If such monitors are 

present, the methods in Section 4.1, Methodology Rank 1 for Stationary Combustion Sources, should be 

used to calculate emissions. Although it is unlikely that CEMS are used that can provide emissions for 

speciated organic compounds, if a facility monitors THC and has sampled the organic vapors to determine 

specific organic compound concentrations, then speciation profile developed from the sampling data can 

be used with the CEMS data for THC. The THC emissions would be reported as Methodology Rank 1A 

for loading operations and the speciated organic emissions would be reported as Methodology Rank 1B 

for loading operations. 
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9-3 

9.3 Methodology Ranks 2 and 3 for Loading operations 

Performance testing conducted at the refinery may be used to develop site-specific emission factors with 

emission data correlated to throughput. These site-specific emission factors may be used with throughput 

data to estimate the annual loading emissions. 

For gasoline loading activities regulated under Petroleum Refinery MACT I (40 CFR Part 63, Subpart CC 

and Subpart R), refineries have conducted periodic EPA Method 18, Method 25A, or Method 25B testing 

for speciated hydrocarbons or for outlet nonmethane organic compounds (NMOC); determined the flow 

rate based on EPA Method 2A or 2B testing; and measured and recorded the gasoline loading throughput 

during the testing. The outlet test results on a mass basis are correlated with the gasoline throughput 

during the test to demonstrate that the refinery is meeting the 10 mg/L gasoline emission limitation. The 

test data could also be used to estimate the speciated hydrocarbons, total hydrocarbon, CH4, NMOC, or 

VOC loading emissions into the atmosphere based on the mass emissions per volume loaded factor 

developed during the performance test and the annual quantity of that product loaded. It is important to 

note that when NMOC is used, a CH4 emission factor may also be developed. Additional information 

about speciation of the gasoline or product either as site-specific information or as defaults may be used 

to estimate individual species component emissions. 

For marine vessel loading regulated under the Marine Vessel Loading MACT (40 CFR Part 63, Subpart 

CC and Subpart Y), refineries have conducted EPA Method 2, 2A, 2C, or 2D flow rate testing and have 

conducted EPA Method 25 or 25A testing on the inlet and outlet streams of the control device to 

determine control device efficiency. The Marine Vessel Loading MACT requires initial performance 

testing of the control device, but it does not require ongoing or periodic testing. The outlet test data, along 

with the recorded product throughput during the testing, could also be used to estimate the total 

hydrocarbon, CH4, NMOC, or VOC loading emissions per volume loaded factor. This factor and the 

annual loading data of the product can be used to estimate emissions. It is important to note that when 

NMOC is used, a CH4 emission factor may also be developed. Additional information on speciation of the 

gasoline or product either as site-specific information or as defaults may be used to estimate individual 

species component emissions. 

The data necessary to implement Methodology Ranks 2 and 3 for loading operations include the emission 

rate or emission factor (either speciated by component or as total hydrocarbon, CH4, NMOC, or VOC) 

and throughput data of the products loaded. Table 9-2 summarizes the data requirements of Methodology 

Ranks 2 and 3. 

Table 9-2. Data Requirements for VOC or Speciated Emissions, Methodology Rank 1 or 2 

Rank Data That Must Be Collected The Way in Which Data Are Obtained 

Rank 2—

speciated 

emissions 

 Speciated component emission factor 

for a product (milligrams per liter [mg/L] 

or lb/gal) 

 Periodic EPA Method 18 testing results 

 Throughput data by product over the 

time period of interest (gallons or liters) 

 Volume flow rate measurements determined by 

flow meter or pump rates, gallons, or liters 

Rank 3—

VOC or total 

hydrocarbon 

emissions 

 Total hydrocarbon or VOC emission 

factor for a product (mg/liter or lb/gal) 

 Periodic EPA Method 25 or 25A testing results 

 Spectiaion profile from measurement data or from 

process knowledge 

 Throughput data by product over the 

time period of interest (gallons or liters) 

 Volume flow rate measurements determined by 

flow meter or pump rates, gallons, or liters 
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Equation 9-1 should be used to estimate the emissions of each product using emission rates or emission 

factors developed from testing. 

E ER Thruput Li = Li × (Eq. 9-1) 

where: 

 ELi = Emissions of component species “i” (lbs) 

 ERLi = Emission rate of component species “i” (lb/gal) 

 Thruput = Throughput of product (gallons) 

When ERLi is based on total hydrocarbon, NMOC, or VOC, pollutant “i” is simply the total hydrocarbon, 

NMOC, or VOC. When ERLi is based on single pollutant, pollutant “i” will be the individual pollutant. 

When ERLi is based on total hydrocarbon, NMOC, or VOC (i.e., Method 25, 25A, or 25B testing), 

additional calculations are necessary to estimate individual pollutant emissions. To estimate the emissions 

of each pollutant, multiply Equation 9-1 for ELi by the vapor weight fraction of the component “i”, as 

shown in Equation 9-2. 

ELSpecies = ERLi ×Thruput ×WtfracSpecies (Eq. 9-2) 

where: 

 ELSpecies = Emissions of component species “i” (lbs) 

 WtfracSpecies = Vapor weight fraction of component species “i” (fraction by weight) 

If the vapor weight fraction of the components are not know, then these concentrations can be calculated 

from the product knowledge, i.e., the composition of compounds in the liquid. Appendix A, Average 

Stream Compositions, presents the methodology for calculating the vapor phase concentration based on 

the liquid-phase composition and the system temperature and pressure. It is important to characterize even 

low levels of the most volatile compounds in the liquid, because even low levels of the most volatile 

compounds can significantly affect the vapor phase concentration. An example calculation is provided in 

Example A-1 of Appendix A. 

9.4 Methodology Rank 4 for Loading operations 

The emission estimating methodology for loading operations is given in AP-42 (U.S. EPA, 1995a); these 

methodologies are for loading operations that are vented directly to the atmosphere. Equations are 

provided in this section for estimating controlled emissions from the “uncontrolled” emissions based on 

the capture and control efficiency. In section 5.2 of AP-42, commodities are categorized into crude 

loading, gasoline loading, and what is termed “other products” (i.e., not crude or gasoline). In the AP-42 

methodology, there is one equation that is used for tanker trucks and rail cars for crude, gasoline, and 

other commodity products and for marine vessels for other commodity products (but not for crude or 

gasoline). In addition, Table 5.2-2 in AP-42 presents other emission factors that are used for marine 

vessels for gasoline. These equations provide the emissions for the “product” or “total hydrocarbon,” 

whether that product has multiple component species (e.g., gasoline) or whether that product is a single 

species (e.g., toluene). Depending on the commodity being loaded, the emission factor (EFL) could be 

used for gasoline emissions, crude emissions, or other product emissions. The AP-42 methodology for 

gasoline and other products is summarized in the following sections. It is not expected that refineries will 

be loading crude for transport, but if so, the refiner should consult AP-42 for the emission estimation 

methodology. 
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9-5 

9.4.1 AP-42 Emission Factors for “Product” or “Total Hydrocarbon” Emissions 

9.4.1.1 Tanker Trucks and Railcars (Any Commodity) and Marine Vessels (Products 

Other than Gasoline and Crude Oil) 

Equation 9-3 should be used to estimate the uncontrolled emission factor or the emission rate for the 

product loaded, in terms of total hydrocarbon or the product: 

T

S P MW

ER Vap

L

× × = 12.46× (Eq. 9-3) 

where: 

 ERL = Loading emission factor or emission rate for the product (or total hydrocarbon) loaded 

(in lb per 103

 gallons of liquid loaded) 

 S = Saturation factor (see Table 9-3) 

 P = True vapor pressure of liquid loaded (pounds per square inch absolute [psia])1

 MWVap = Molecular weight of vapors (lb/mol) 

 T = Temperature of bulk liquid loaded (°R; °F + 460) 

Table 9-3. Saturation Factorsa

Type of Tanker Loaded Loading Scenario Saturation Factor 

 Tank trucks 

 Rail cars 

 Any commodity 

 Submerged loading 

 Dedicated normal service 

0.60 

 Submerged loading 

 Dedicated vapor balance service 

1.00 

 Splash loading 

 Dedicated normal service 

1.45 

 Splash loading 

 Dedicated vapor balance service 

1.00 

 Marine vessels 

 Other products (only) 

 Submerged loading 

 Ships 

0.2 

 Submerged loading 

 Barges 

0.5 

a

 Source: U.S. EPA, 1995. 

9.4.1.2 Marine Vessels (Gasoline) 

Section 5.2, Table 5.2-2, of AP-42 provides VOC emission factors for marine vessels loading gasoline at 

marine terminals based on measurements of gasoline loading losses from ships and barges. Those 

emission factors are presented in Table 9-4. (Table 5.2-2 of AP-42 also includes emission factors in units 

of mg/L.) AP-42 does not provide ratings for these emission factors. 

 

1

 True vapor pressure is defined as the equilibrium partial pressure exerted by a volatile organic liquid as a function 

of temperature. It differs from the Reid vapor pressure, which is defined as the absolute vapor pressure exerted by a 

liquid at 100°F and is a common measure of the volatility of petroleum liquids. For a pure component at 100°F, the 

true vapor pressure is equivalent to the Reid vapor pressure. 
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Table 9-4. VOC Emission Factors for Marine Vessel Loading of Gasoline at Marine Terminalsa

Vessel Tank Condition Previous Cargo 

Ships and Ocean Barges 

(lb/103 gal) Barges (lb/103 gal) 

Uncleaned Volatilec 2.6 3.9 

Ballasted Volatile 1.7 Not applicable 

Cleaned Volatile 1.5 No data 

Gas-freed Volatile 0.7 No data 

Any condition Nonvolatile 0.7 No data 

Gas-freed Any cargo No data 2.0 

Typical overall situationd Any cargo 1.8 3.4 

a

 Source: U.S. EPA, 1995a. The emission factors for VOC (which excludes methane and ethane) may be used 

to estimate total organic emissions (i.e., including methane and ethane) because methane and ethane 

constitute a negligible fraction of the components in gasoline. b

 Ocean barges (tank compartment depth about 40 ft) exhibit emission levels similar to tank ships. Shallow draft 

barges (compartment depth 10 to 12 ft) exhibit higher emission levels. c

 Volatile cargoes are those with a true vapor pressure greater than 10 kilopascals (kPa) (1.5 psia). d

 Based on observation that 41% of tested ship compartments were uncleaned, 11% ballasted, 24% cleaned, 

and 24% gas-freed. For barges, 76% were uncleaned. 

9.4.2 Estimate Uncontrolled Emissions and Speciate 

Using the emission factor developed or identified from the methods previously discussed, the emissions 

can be estimated based on Equation 9-4: 

E ER Thruput L = L × (Eq. 9-4) 

where: 

 EL = Uncontrolled emissions (lb) of commodity 

 ERL = Loading emission rate (lb/103

 gal of liquid loaded) 

 Thruput = Throughput of commodity (gallons) 

As previously discussed, depending on the commodity being loaded, the emission rate ERL could be for 

gasoline, crude, or other product. Also as previously discussed, to speciate the emissions for specific 

components, the composition or concentration data available (i.e., product-specific, product-specific 

average, site-specific product, or default averages) can be used as shown in Equation 9-5. 

ELSpecies = ERL ×Thruput ×WtfracSpecies (Eq. 9-5) 

where: 

 ELSpecies = Emissions (lb) of the component species “i” 

 WtfracSpecies = Weight fraction of component species “i” in the vapor (fraction) 

9.4.3 Capture Efficiency 

If an add-on air pollution control device or vapor balance system is used to capture and control emissions, 

then capture and control efficiencies should be included in the emission estimate. The capture efficiency 

is the portion of the total emissions that is captured by the vapor collection system. The effectiveness of 

the vapor collection system, or capture system, is dependent on the leak tightness of the truck tank, rail 

car, or marine vessel; the condition of the connection from the tanker or vessel collection header 

equipment to the vapor collection system; the leak tightness of the terminal’s vapor collection system; and 

the control device. For gasoline loading racks subject to Subpart CC, refineries are required to confirm 
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9-7 

and document the vapor tightness of the vehicles being loaded. For loading racks subject to gasoline 

loading requirements, an annual pressure and vacuum certification is required on the tanker truck (e.g., 

using EPA Method 27 in 40 CFR Part 60), a leak test using EPA Method 21 from 40 CFR Part 60 may be 

performed on the tanker truck, and a leak check using EPA Method 21 may be conducted on the 

terminal’s vapor collection system. In addition, the type of loading conducted (i.e., atmospheric, 

pressurized) and type of connection from the tank headspace to the vapor collection system and to the 

control device are factors. Typical capture efficiencies assumed for vapor collection procedures and 

systems are shown in Table 9-5. Capture efficiency for the vapor collection system can be applied based 

on the leak check conducted for the tanker truck, rail car, and marine vessel. 

Table 9-5. Capture Efficiencies for Vapor Collection Systemsa

Loading Characteristics and Leak Check Frequency for Tankers Capture Efficiencies 

 No leak check on tanker 65% 

 No leak check on tanker 

 Maintain minimum positive pressure below +3 to +5 inches of water 

85% 

 Annual leak check on tanker per 40 CFR Part 60, Subpart XX (nongasoline) 95% 

 Semi-annual leak check on tanker per 40 CFR Part 60, Subpart XX (nongasoline) 97.5% 

 Annual leak check on tanker per 40 CFR Part 60, Subpart XX (gasoline) 98.7% 

 Vacuum loading, maintaining vacuum less than −1.5 inches of water 

 Hard-piped bolted, flanged connection from tanker to the vapor collection system 

100% 

 Pressure tank that is U.S. Department of Transportation certified 

 Hard-piped bolted, flanged connection from tanker to the vapor collection system 

100% 

Note: Use latest available version if updates to this document have occurred since the cited version. a

 Source: TCEQ, 2000. 

9.4.4 Overall Control Efficiency 

The overall control efficiency represents the portion of the total captured emissions that are removed from 

the emission stream by the add-on air pollution control device. The control efficiency determined for the 

control device should be applied based on performance testing, if available, or based on design efficiency 

and operating parameters. 

To estimate controlled emissions from loading, use Equations 9-6 and 9-7 to apply the capture efficiency 

and the control efficiency to the uncontrolled emissions: 

E ER Thruput ( Capture ) ( CE ) Cont = L × × 1− × 1− (9-6) 

E ER Thruput Wtfrac ( Capture ) ( CE ) ContSpecies = L × × Species × 1− × 1− (9-7) 

where: 

 Capture = Capture efficiency of the vapor collection system (fraction) 

 CE = Control efficiency of the add-on air pollution control device (fraction) 
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9-8 

Example 9-1: Calculation for Rank 4—When Property Data Are Not Available 

Calculate the VOC and HAP emissions for submerged loading of reformulated gasoline into 

dedicated-service gasoline transport tank trucks (each with a volume of 8,000 gallons) based 

on the following information: 

The refinery loads 210 tank trucks per year, with 100 tank trucks loading gasoline at a bulk 

temperature of 90°F, 55 loading at a bulk temperature of 77°F, and 55 loading at a bulk 

temperature of 40°F. Liquid composition or vapor-phase property data are not available,so the 

property data for liquid composition of reformulated gasoline in Appendix A are used (see 

Tables A-1 and Table A-2). 

First, the vapor pressure of reformulated gasoline and MWVAP must be calculated. In this 

example, the weight fraction of the vapor is estimated separately for each loading temperature 

following the calculation methodology presented in Appendix A (see Example A-1 and Table 

A-2). The vapor pressure for each constituent is determined at the three loading temperatures 

using Antoine’s equation and Antoine’s coefficients, such as those provided in Table 7.1-5 of 

AP-42 (U.S. EPA, 1995a). 

From Example A-1 in Appendix A, at 77°F, the total system vapor pressure is 4.77 psia and 

the MW of the vapor, MWGasolineVAP, is 67.49 lb/lb-mol. Similar calculations for loading 

gasoline with bulk temperatures of 90°F and 40°F reveal the following (see Appendix A for 

further details): 

Temperature Vapor Pressure MWGasolineVAP

90°F 6.13 psia 68.08 lb/lb-mol 

77°F 4.77 psia 67.49 lb/lb-mol 

40°F 2.17 psia 65.79 lb/lb-mol 
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9-9 

Example 9-1 (continued): Calculation for Rank 4—When Property Data Are Not 

Available 

The emissions rates at each temperature are calculated using Equation 9-3: 

( ) 5.673 lb/10 gal 90°F 460 °R

lb mole

lb 0.60 6.13psia 68.08

12.46 3

90 = +

− × ×

ERGasoline =

( ) 4.482 lb/10 gal 77 F 460 °R

lb mole

lb 0.60 4.77psia 67.49

12.46 3

77 = ° +

− × ×

ERGasoline =

( ) 2.135 lb/10 gal 40 F 460 °R

lb mole

lb 0.60 2.17psia 65.79

12.46 3

40 = ° +

− × ×

ERGasoline =

The emissions at each temperature are then calculated using Equation 9-4: 

100 trucks 4,538 lb gasoline truck

gal 8,000

1,000 gal

5.673 lb

90 ⎟ =

⎠

⎞ ⎜

⎝

⎛ EGasoline = × ×

55 trucks 1,972 lb gasoline truck

gal 8,000

1,000 gal

4.482 lb

77 ⎟ =

⎠

⎞ ⎜

⎝

⎛ EGasoline = × ×

55 trucks 939 lb gasoline truck

gal 8,000

1,000 gal

2.135 lb

40 ⎟ =

⎠

⎞ ⎜

⎝

⎛ EGasoline = × ×

The individual VOC or HAP species at each bulk temperature can be estimated using the 

calculated gasoline vapor weight fraction for each species in Equation 9-5: 

ELSpecies = EFL ×Thruput ×WtfracSpecies = Egasoline ×WtfracSpecies

See Table 9-6 for the emission estimate summary for individual HAP species. 

Finally, total emissions are estimated by summing the emission estimates for each of the three 

bulk temperatures. Total gasoline emissions (VOC) are 7,449 lb (4,538 lb + 1,972 lb + 939 

lb), or 3.7 tons (7,449 lb ÷ 2,000 lb/ton). 

Similarly, total emissions of each of the individual HAP species are estimated by summing the 

emission estimates for each of the three bulk temperatures. The results are presented in 

Table 9-6. 
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9-10 

Table 9-6. Sample Calculation Methodology Rank 4—Summary of Emissions (When Property Data Are N

CAS 

Number Component “i” 

At 40°F 

Gasoline, 

Vapor, 

wt% 

At 40°F 

EGasoline = 939 lb

ELSpecies “i” (lb) 

At 77°F 

Gasoline, 

Vapor, 

wt% 

At 77°F 

EGasoline = 1,972 lb

ELSpecies “i” (lb) 

At 90°F 

Gasoline, 

Vapor, 

wt% 

At 90

EGasoline = 

ELSpecies 

71-43-2 Benzene 0.33 3.14 0.42 8.24 0.45 

110-54-3 Hexane 0.96 9.05 1.13 22.30 1.18 108-88-3 Toluene 0.77 7.23 1.09 21.55 1.21 

1330-20-7 Xylene 0.22 2.02 0.35 6.93 0.41 

100-41-4 Ethylbenzene 0.04 0.38 0.07 1.30 0.08 540-84-1 2,2,4-Trimethylpentane 0.23 2.15 0.30 5.87 0.32 

98-82-8 Cumene 0.0027 0.025 0.0048 0.094 0.0057 91-20-3 Naphthalene 0.0001 0.001 0.0003 0.006 0.0004 

Total HAP 24.0 66.3 
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10-1 

10. Fugitive Dust Sources 

There are three main sources of fugitive dust (or PM) at a petroleum refinery: roads (paved and unpaved); 

fluid catalytic cracking catalyst handling; and petroleum coke storage and handling. Petroleum refineries 

may also operate a landfill or land application unit, which would also be a source of fugitive PM 

emissions. There are no direct emission measurement methodologies commonly employed for fugitive 

dust sources. Fugitive dust sources are described in Chapter 13 of AP-42 (U.S. EPA, 1995a). 

Unfortunately, none of the default factors for the fugitive dust emission correlations are specific to 

petroleum refineries. Table 10-1 provides recommended default values for the correlations based on a 

review of the available data. The methodologies are detailed in Chapter 13 of AP-42 and basic guidance 

for applying the methodologies are provided below. 

 For paved roads, Equation 1 of Section 13.2.1.3 of AP-42 (U.S. EPA, 1995a) should be used with 

the silt loading recommended in Table 10-1; values for all other equation variables are provided 

in Section 13.2.1.3. 

 For unpaved roads, Equation 1a and 1b of Section 13.2.2.2 of AP-42 (U.S. EPA, 1995a) should 

be used with the silt content recommended in Table 10-1; values for all other equation variables 

are provided in Section 13.2.2.2. 

 For handling of FCCU catalyst or petroleum coke, use Equation 1 of Section 13.2.4.3 of AP-42 

(U.S. EPA, 1995a) with the moisture content recommended in Table 10-1; values for all other 

equation variables are provided in Section 13.2.4.3. 

Table 10-1. Default Values for Fugitive Dust Emission Estimates 

Source/Variable Description 

Potential Range 

Value 

Recommended 

Value 

Paved road : silt loading, g/m2 0.4a – 120b 10 

Unpaved road : silt content % 1.8 – 25.2c 7 

FCCU catalyst “drops”: silt content % 50d

FCCU catalyst “drops”: moisture content % 8e

FCU or calcined coke “drops”: silt content % 5e

FCU coke or calcined “drops”: moisture content % 8e

Delayed coking unit coke “drops”: silt content % 5e

Delayed coking unit coke “drops”: moisture content % 10f

Flexicoking or petroleum coke ash: silt content % 13g

Flexicoking or petroleum coke ash: moisture content % 7g

a

 Based on low average daily traffic (ADT) public road factor in Table 13.2.1-3 in AP-42. 

b

 Based in asphalt batching industrial facility factor in Table 13.2.1-4 in AP-42. c

 Based on range for industrial sites in Table 13.2.2-3 in AP-42. d

 Assumed based on median particle size of FCCU catalyst and equilibrium catalyst (E-cat) of 65 μm. e

 Values for coke breeze assumed to apply. 

f

 Value suggested as typical by industry representatives (API/NPRA, 2010). 

g

 Values for flue dust assumed to apply. 

The methodologies outlined in Chapter 13 provide means of estimating PM10 and PM2.5 emissions. These 

emissions are all filterable PM so that PM10-PRI = PM10-FIL and PM25-PRI = PM25-FIL. For FCCU 

catalyst handling emissions and for petroleum coke handling activities, emission estimates should also be 

provided for metal HAP emissions. Concentrations of specific metal HAP are commonly determined for 

the FCCU equilibrium catalyst; these concentrations can be used times the PM10 emission rate to 
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Final ICR Version – Corrected Section 10—Fugitive Dust Sources 

10-2 

determine the metal HAP emission rate from FCCU catalyst and E-cat handling (external from the 

FCCU). Table 5-3 provides concentration ratios of various metal HAP to nickel on CCU fines. These 

concentration ratios can be used to augment the FCCU catalyst and E-cat metal HAP emission estimates 

when only nickel concentrations are routinely determined. Compositional analysis of petroleum coke 

material or ash should also be determined so that the metal HAP emissions from petroleum coke or ash 

handling can be reported. 
Version 2.1.1 

Final ICR Version – Corrected Section 11—Startup and Shutdown 

11-1 

11. Startup and Shutdown 

Except for the CEMS-based measurements (i.e., Methodology Rank 1), most of the emission estimation 

methods provided in this Refinery Emissions Protocol document characterize the emissions during 

normal operating conditions. However, during startup and shutdown, the process operations are not 

normal. During startup, the reactor temperatures may not be sufficient for the necessary reactions to occur 

or the process flow rate may be well below typical operating conditions. Under these conditions, 

processes that do not typically have atmospheric emissions may have significant emissions. While most 

control devices will operate well at lower vent rates, some control devices, such as venturi scrubbers, 

require a minimum flow for effective operation. During startup and shutdown, the emission 

characteristics of the processes may be significantly different than those during normal operations. When 

the emission estimation methodology relies on normal operating conditions (e.g., most site-specific and 

default emission factors), it is important to specifically estimate the emissions during startup and 

shutdown and include these emissions in the facility’s annual emission totals. During shutdown, the 

process vessels need to be degassed and purged. 

Process unit startup and shutdown of one process unit may also affect the emission characteristics of other 

units, particularly with respect to the fuel gas system. When a hydrotreater or hydrocracking unit is 

shutdown, this often leads to excess hydrogen being added to the fuel gas. This leads to higher NOx

emissions from process heaters. When certain energy intensive units, such as catalytic reforming units, 

are shutdown, the refinery may have excess fuel gas, which is subsequently flared. Depending on the 

methods used to estimate emissions from combustion sources and flares, these fuel gas fluctuations may 

already be fully accounted within the inventories for combustion sources and flares. However, if default 

estimates (or site-specific estimates based on source tests conducted under typical operating conditions) 

are used, then emissions during these significant fuel gas fluctuation events should be estimated and the 

emissions included in the annual emission values. 

It is beyond the scope of this protocol document to provide methods of estimating emissions during all 

startup or shutdown events. However, the primary emission event during startup or shutdown is expected 

to be vessel depressurization and purging (or degassing). Methods are provided in this section to account 

for these events are described in this section. 

11.1 Gaseous Process Vessel Depressurization and Purging 

Process vessel depressurization for gaseous processes can be estimated using Equation 11-1. This 

equation assumes ideal gas law; for gases that do not follow ideal gas law, compressibility factors can be 

included. The equation includes a void fraction term to account for inert material, such as packing 

material, distillation trays, and certain catalyst particles, that reduce the gaseous space. This equation may 

underestimate the emissions if the solid material in the vessel may adsorb certain gas constituents (e.g., 

petroleum coke or activated carbon), that can desorb at lower pressures and temperatures. 

( ) [ ] ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

× × × × ° ×

+ = i

i

V void

V

V

i MF

MVC

MW V f T

P

E 528 R

14.7

14.7

 (Eq. 11-1) 

where: 

 Ei = Emissions of pollutant “i” during depressurization event (lbs/event). 

 PV = Gauge pressure of the vessel when depressurization gases are first routed to the 

atmosphere (pounds per square inch gauge, psig). 

 14.7 = Assumed atmospheric pressure (pounds per square inch, psi). 

 TV = Absolute temperature of the vessel when depressurization gases are first routed to the 

atmosphere (degrees Rankine, °R). 
Version 2.1.1 

Final ICR Version – Corrected Section 11—Startup and Shutdown 

11-2 

 528 = “Standard” temperature used in the calculation (°R). 

 VV = Volume of the vessel (cubic feet, ft3

). 

 fvoid = Volumetric void fraction of vessel. Use 1 unless packing material or trays are present 

in the vessel. 

 MWi = Molecular weight of pollutant “i” (lb/lb-mole). 

 MVC = Molar volume conversion factor (385.3 scf/ lb-mole). 

 MFi = Volume fraction of pollutant “i” in vessel gas (scf pollutant i/scf of gas). 

Typically, depressurization and purging occurs initially to the refinery fuel gas system or a flare or similar 

control device. Combustion of gases purged to the refinery fuel gas system (either directly or via a flare 

gas recovery system) should be accounted for under stationary combustion source emissions regardless of 

the methodology used for stationary combustion sources. Depending on the methodology used to estimate 

the emissions from the flare, these gas flows may or may not be included in the flare emission estimates. 

If the flow rate and composition or heating value of the flare gas is measured (Methodology Ranks 1, 2 or 

3 for flares), special calculations are not needed because episodic releases to the flare, such as those from 

depressurization and purging events, are adequately accounted for. If the flare emission methodology 

does not account for these flows (e.g., default factors in Methodology Rank 6 for flares), Equation 11-1 

can be used to estimate the mass of gas sent to the flare or other control device (using initial 

depressurization temperatures and pressures) and these mass rates can be adjusted by the flare or control 

device efficiency to estimate the emissions during the controlled venting period. The use of Equation 11-1 

is illustrated in Example 11-1, Gaseous Depressurization Calculation. 

11.2 Liquid Process Vessel Depressurization and Purging 

For vessels that contain liquids, depressurization and purging emissions can be estimated based on the 

“heel” or fraction of the liquid that remains in the vessel prior to purging. This method assumes that the 

mass of liquid remaining in the tank will overwhelm the quantity of contaminants in the headspace. For 

systems operating with very volatile material (such as butane in gasoline), it may be necessary to consider 

the initial gaseous emissions for the most volatile components (using Equation 11-1) as well as the liquid 

heel. A heel fraction may be between 0.1 and 1 percent, depending on the viscosity of the liquid, the 

surface area of internals within the vessel, and the location of the drainage port or pump line (higher 

viscosities, higher internal surface areas, and higher drainage port locations will increase the heel 

fraction). Using the heel method, it is assumed the entire liquid heel is eventually volatilized. Knowledge 

of the process stream can be used to speciate the emissions. Again, some of the heel may be purged to a 

flare or other control device and a control efficiency for this portion is warranted, but some fraction will 

also be purged directly to the atmosphere. Example 11-2, Liquid Heel Emissions Calculation, illustrates 

this methodology. 
Version 2.1.1 

Final ICR Version – Corrected Section 11—Startup and Shutdown 

11-3 

Example 11-1: Gaseous Depressurization Calculation 

A catalytic reforming unit is depressurized and purged to a flare. After the purge sequence, no 

liquid materials are assumed to be present. The reactor is then depressurized and purged to the 

atmosphere. The total volume of the reactor vessels are 20,000 ft3 and the catalyst occupies 

40% of the total reactor volume. The temperature and pressure of the vessel when first purged 

to the atmosphere are 250°C and 10 psig, respectively. The composition of the gas is in the 

reactor vessel after the flare purge is: 

Benzene = 1.2 vol% 

Hexane = 0.5 vol% 

Toluene = 1.4 vol% 

Xylenes = 0.8 vol% 

Other VOC = 2.1 vol% 

Nitrogen = 94 vol% 

For use in Equation 10-1, the reactor vessel temperature must be converted to °R: 250°C = 

250×9/5 + 32 = 482°F = 482+460 = 942°R. 

The void fraction is the volume fraction not occupied by catalyst particles: 1-0.4 = 0.6. 

The molecular weight of the constituents listed range from 78 to 106 lb/lb-mol. It is assumed 

the “other VOC” has similar molecular weight so a molecular weight for this unspecified 

material is estimated from, the weighted average molecular weight of the known organic 

constituents: MolWt “other VOC” = (1.2×78+0.5×86+1.4×92+0.8×106)/4.9 = 90 lb/lb-mol. 

Using benzene as the example, substituting into Equation 11-1 yields: 

( ) [ ] 0.01 27.5 lbs 0.014 tons

385.3

78 20000 0.6

942

528 R

14.7

10 14.7 ⎟ = = ⎠

⎞ ⎜

⎝

⎛

× × × × ° ×

+ Ei =

Similarly, the emissions of other organic constituents are estimated to be: 

Benzene = 27.5 lbs/event 

Hexane = 12.6 lbs/event 

Toluene = 37.8 lbs/event 

Xylenes = 24.9 lbs/event 

Other VOC = 55.4 lbs/event 

The total VOC is the sum of these emissions, which is 158 lbs/event or 0.079 tons/event. If 

this event occurred twice during the year, the annual emission would be 0.16 tons VOC/yr. 
Version 2.1.1 

Final ICR Version – Corrected Section 11—Startup and Shutdown 

11-4 

Example 11-2: Liquid Heel Emissions Calculation 

Problem: Using the same catalytic reforming unit as in Example 11-1, estimate the emissions 

from depressurizing and purging the reactor vessels using the “heel” approach. Assume 90 

percent of the heel is purged to the flare. 

Solution: As there is high internal surface area, the heel is assumed to be 0.5% of the liquid 

volume. The maximum liquid volume is 20,000 ft3 × (1-0.4) = 12,000 ft3, so the volume of 

liquid in the reactor is estimated to be 60 ft3

 (12,000 × 0.005). 

Appendix A contains average composition of various process fluids. Reformate composition is 

given as: 

Benzene = 4.6 wt% 

Hexane = 3.9 wt% 

Toluene = 14.5 wt% 

Xylenes = 13.8 wt% 

Other VOC = 63.2 wt% 

To calculate the potential mass emissions, a mass of liquid remaining must be calculated. 

Using a specific gravity of 0.8 for reformate, the mass of liquid remaining is estimated to be: 

60 ft3

 × 0.8 × 62.4 lb/ft3 (density of water) = 3,000 lbs. 

Given 90 percent of the heel liquid is removed while purging to the flare, then 2,700 lbs of 

material is sent to the flare and 300 lbs are purged directly to the atmosphere. Assuming a 98 

percent destruction efficiency for the flare, the uncombusted emissions from the flare are 

estimated to be 54 lbs [2700×(1-0.98)]. 

Therefore, a total of 354 lbs of organic material (VOC) is estimated to be emitted considering 

emissions from both the flare and atmospheric purging. 

Emissions of specific constituents are calculated based on the mass composition in the liquid: 

Benzene = 354 ×0.046 = 16 lbs/event 

Hexane = 354 ×0.039 = 14 lbs/event 

Toluene = 354 ×0.145 = 51 lbs/event 

Xylenes = 354 ×0.138 = 49 lbs/event 

Other VOC = 354 ×0.632 = 224 lbs/event. 
Version 2.1.1 

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12-1 

12. Malfunctions/Upsets 

Malfunctions or upsets may occur either within the process unit or to a control device used to reduce a 

source’s emissions. During malfunction/upset events (hereafter simply referred to as malfunction events), 

emissions may be significantly higher than the emissions that occur under normal operating conditions. 

Except for the CEMS-based measurements (i.e., Methodology Rank 1), most of the emissions estimation 

methods provided in this Refinery Emissions Protocol document characterize the emissions during 

normal operating conditions. As such, emissions during malfunction events must be accounted for 

separately for each malfunction event and these malfunction/upset emissions must be added to the normal 

process emissions to accurately estimate annual emissions. 

Because of the myriad of potential malfunction events that could occur, it is impossible to provide 

specific guidance for all possible malfunction scenarios. However, because malfunction events are 

important to both annual and short-term emissions, the duration and emissions associated with each 

malfunction event should be recorded, and these emissions should be included in the annual emissions 

reported in response to the ICR. 

The following list provides specific events for which malfunction/upset emissions estimates should be 

made to accurately account for these emissions. Again, this is not intended to be an exhaustive list, but 

rather representative examples. In some malfunction events, such as pressure relief valve opening to a 

flare during a system over-pressurization event, the emissions during the malfunction event may be 

adequately accounted for by the flare emission methodology (i.e., when using continuous monitoring of 

gases is sent to a flare), but in other cases it may not (i.e., when using default factors). As such, emissions 

inventory developers will need to evaluate the malfunction events in light of their inventory methods to 

determine if it is appropriate to use special malfunction emission calculations. Emission estimates should 

be provided for the following malfunction events: 

1. Any instance when a control device is bypassed or is not functioning properly. 

2. Any instance when the amine scrubbing system and/or sulfur recovery plant is offline or not 

operating at normal efficiencies (generally affecting SO2 emission estimates from combustion 

sources, flares, and/or sulfur recovery plants). 

3. Instances of over-steaming a flare (steam-to-gas ratios exceeding 4) or instances where the flare 

operating conditions do not satisfy 40 CFR 60.18 (i.e., inadequate BTU content, exit velocities 

exceeding limits). Eighty percent flare destruction efficiencies should be used during periods of 

over-steaming; 93 percent flare destruction efficiencies should be used during periods when the 

flare operating conditions do not satisfy 40 CFR 60.18. 

4. Any instance when a spill or similar emergency release occurs. 

Leaks identified as part of a LDAR work practice (for equipment leaks or cooling towers) are not 

considered malfunction events, and these emissions are covered using the methodologies presented in 

Section 2, Equipment Leaks, and Section 8, Cooling Towers, of this Refinery Emissions Protocol 

document. Note, however, the methodology for spills presented in this section can be used for estimating 

emissions from equipment leaks that result in liquid puddles. As noted in Section 3, Storage Tanks, of this 

Refinery Emissions Protocol document, specific calculations should be made for tank roof landings. The 

emissions from tank roof landings are independent of the cause of the landing (intentional or 

unintentional), so there is no need to distinguish between landings that occur as a result of a “malfunction 

event” or for another reason. 

There are three types of malfunction events considered in this section: control device malfunctions; 

process vessel overpressurization; and spills. 
Version 2.1.1 

Final ICR Version – Corrected Section 12—Malfunctions/Upsets 

12-2 

12.1 Control Device Malfunctions 

When a control device is used to reduce the emissions from a particular source, the site-specific emission 

factors or other methodologies provided in this Refinery Emissions Protocol document account for these 

controls when the equipment is operating normally. However, when control systems are not operating 

normally or or bypassed the emissions may be orders of magnitude more than when these emissions are 

controlled. If a control device that normally achieves 99% control efficiency is offline for 3 days, then the 

emissions during these 3 days would equal the annual emissions projected for the controlled emission 

source. 

When there is a malfunction with a control device, the emissions from the source can be estimated based 

on the uncontrolled emission factor or by adjusting the controlled emissions based on the control device’s 

efficiency. It is important to note that the control device efficiency is often different for different 

pollutants. A wet scrubber on an FCCU may be 95% efficient at reducing SO2 emissions, 90% efficient 

for PM and metal HAPs, but has no real impact on VOC or NOX emissions. Similarly, oversteaming a 

flare that causes poor combustion efficiency will increase VOC and reduced sulfur emissions but reduce 

NOX and SO2 emissions. Table 12-1 provides default control efficiencies and correction factors for 

certain control device malfunctions. If site-specific emission data are available for the controlled 

emissions, then the “uncontrolled” emissions during the control device malfunction or bypass can be 

estimated using Equation 12-1. 

E E EM t unc,i = cont,i × cont,i × (Eq. 12-1) 

where: 

 Eunc,i = Uncontrolled emissions estimate from control device malfunction or bypass for 

pollutant “i” (kg/event) 

 Econt,i = Controlled emission rate of pollutant “i” from measurement data or site-specific 

emission test data (kg/hr) 

 EMcont,i = Controlled emission multiplier for pollutant “i” based on the source on control device 

from Table 12-1 

 t = Duration of the event (hr/event). 

Table 12-1. Control Device Efficiency and Multiplier Factors for Control Device Malfunctions 

Source/Control Device 

Descriptiona Pollutant Classb Control Device Efficiencyc (%) 

Controlled 

Emission 

Multiplierd

FCCU or FCU/wet scrubber PM, metal HAP 92 12.5 

 SO2 95 20 

FCCU or FCU/ESP PM, Metal HAP 92 12.5 

SO2, NOX, VOC, organic 

HAP, CO 

0 1 

FCCU or FCU/cyclone PM, Metal HAP 85 6.7 

FCCU or FCU/CO boiler CO, VOC, most organic HAP 98% 50 

 NOX, PAH, Formaldehyde -100% 0.5 

FCCU or FCU/SCR NOX 92 12.5 

FCCU or FCU/SNCR NOX 60% 1.7 

(continued) 
Version 2.1.1 

Final ICR Version – Corrected Section 12—Malfunctions/Upsets 

12-3 

Table 12-1. Control Device Efficiency and Multiplier Factors for Control Device Malfunctions 

(continued) 

Source/Control Device 

Descriptiona Pollutant Classb Control Device Efficiencyc (%) 

Controlled 

Emission 

Multiplierd

Sulfur plant malfunction with sour 

gas sent to flare 

SO2 96 – 99.8% 25 - 500 

 H2S 0 – 98% 1– 50 

Tail gas treatment malfunction with 

tail gas sent to flare 

SO2 95% 20 

 H2S 0 – 95% 1 – 20 

a

 Abbreviations: 

FCCU = fluid catalytic cracking unit 

FCU = fluid coking unit 

ESP = electrostatic precipitator 

CO boiler = carbon monoxide boiler 

SCR = selective catalytic reduction 

SNCR = selective non-catalytic reduction b

 Pollutant class. Only pollutants affected by the control device are listed. For other pollutants, assume the 

control device efficiency is 0% and the controlled emission multiplier is 1. c

 Control device efficiency. A negative number indicates a control device that may increase the emissions of a 

particular pollutant. d

 Controlled emission multiplier. Factor used to escalate the controlled emission factor to account for periods of 

control device malfunction = 1/(1-control device efficiency). 

12.2 Vessel Overpressurization 

Process malfunctions often result in temperature or pressure excursions that must be released from the 

vessel to prevent a catastrophic failure. Generally, these emergency releases will be sent to a flare. 

Depending on the methodology used to estimate the emissions from the flare, these gas flows may be 

included in the flare emission estimates (e.g., when measuring flare gas volumes and composition). If the 

flare emission methodology does not account for these flows (e.g., default factors) or if the flow rate 

during the event exceeds the range of the flow meter installed on the flare gas line, then the methods 

provided in this section should be used. 

For discharges through a pressure relief valve or similar discharge of a compressible fluid, the flow 

velocity through the valve, pipe, or other restriction is limited to the speed of sound or Mach 1. 

Discharges that are limited by the speed of sound are termed “choked” or “sonic,” and discharges that are 

less than Mach 1 are termed “unchoked” or “subsonic.” For a pressure relief valve, the outlet pressure is 

typically known, being either atmospheric pressure (14.7 psia) or atmospheric pressure plus the backpressure of the flare system or other control device. To determine if the flow is choked, first use Equation 

12-2 to determine the critical vessel pressure for sonic flow conditions. 

/( 1)

2

1 −

⎟

⎠

⎞ ⎜

⎝

⎛ + ° =

k k

vessel out

k P P (Eq. 12-2) 

where: 

Pvessel° = Critical vessel pressure for sonic flow conditions (atm) 

Pout = Outlet pressure of vent or discharge piping (atm) 

 k = Ratio of the specific heat at constant pressure to the specific heat at constant volume, 

Cp/Cv (dimensionless); see Table 12-2 for values of k for different gases. 
Version 2.1.1 

Final ICR Version – Corrected Section 12—Malfunctions/Upsets 

12-4 

Table 12-2. Values of k for Various Gasesa

Compound k Compound k 

Methane 1.30 Air 1.40 

Natural gas (methane/ethane) 1.27 Hydrogen 1.40 

Ethane 1.22 Nitrogen 1.40 

Ethylene 1.20 Oxygen 1.40 

Propane 1.14 Carbon monoxide 1.40 

n-Butane or Iso-butane 1.11 Carbon dioxide 1.28 

Pentane 1.09 Hydrogen sulfide 1.32 

Hexane or Cyclohexane 1.08 Sulfur dioxide 1.26 

Benzene 1.10 

a

 k = Cp/Cv = ratio of the specific heat at constant pressure to the specific heat at constant volume 

If the actual vessel pressure is less than the critical vessel pressure, Pvessel°, calculated from Equation 12-2, 

then the flow will be subsonic (unchoked). For subsonic flow, first calculate the Mach number of the 

discharge flow using Equation 12-3. 

⎥

⎥

⎥

⎦

⎤

⎢

⎢

⎢

⎣

⎡

− ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛ ⎟×

⎠

⎞ ⎜

⎝

⎛

− =

⎟

⎠

⎞ ⎜

⎝

⎛ −

1

1

2 M

1

k

k

out

vessel

P

P

k (Eq. 12-3) 

where: 

 M = Mach number of the discharge flow 

Pout = Pressure at the discharge outlet, typically atmospheric (atm). 

The mass emissions rate is then calculated using Equation 12-4. 

( )

( ) 2( ) 1

1

2

4

2

M 1 1

M 6.8087 10

−

+

⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛ − +

×

×

× = × × × ×

k

k

vessel

i i vessel

k R T

k MWt E C A P (Eq. 12-4) 

where: 

 Ei = Emission rate of pollutant “i” (lb/sec) 

 Ci, = Concentration of pollutant “i” in the discharged gas (weight fraction) 

 6.8087×104

 = Conversion factor (lb/(ft sec2) per atm) 

 A = Cross-sectional area of the vent outlet (ft2

) 

MWt = Molecular weight of gas discharged (lb/lb-mol) 

 R = Ideal gas law constant = 4.968×104

 (lb ft2)/(sec2 °R lb-mol) 

Tvessel = Temperature of gas in vessel (°R). 

If the vessel pressure is greater than Pvessel°, then the flow will be choked (i.e., limited to sonic flow). 

Therefore, M is set to 1, and Equation 12-4 can be used (with M=1) to calculate the mass emission rate 

during the discharge. 
Version 2.1.1 

Final ICR Version – Corrected Section 12—Malfunctions/Upsets 

12-5 

If the releases are discharged to a flare or other control device (and these discharges are not otherwise 

measured), the calculated mass release rates determined using Equation 12-4 must then be adjusted by the 

control efficiency to estimate the emissions during the emergency release event. 

Equation 12-4 is expressed as an instantaneous emission rate. If the vessel pressure and temperature 

remain fairly constant (less than 5% change) during the event, the instantaneous rate can be multiplied by 

the duration of the release to determine the total emissions for the event. If the vessel pressure and 

temperature vary, Equation 12-4 should be estimated for discrete time intervals and the emissions for each 

time interval determined and summed to calculate the total emissions during the event. 

Example 12-1: Calculation for Emissions for Vessel Overpressurization 

Given: A hydrocracking unit has a 4 inch diameter pressure relief valve set to open at 2,000 psig. 

The gas phase is 50 vol% H2 and 50 vol% light (C2 through C4) hydrocarbons. If the pressure 

relief valve opened for 30 minutes, what are the VOC emissions from the unit during the event? 

Assume the vessel discharges to a flare with an average back pressure of 10 psig. The average 

temperature and pressure of the vessel during the event were 400 °C and 2,050 psig, respectively. 

Solution: Pout = 10+14.7 = 24.7 psia. On a mass basis, most of the flow will be the hydrocarbons. 

Therefore, the k value for propane of 1.14 is selected from Table 2-2 as representative of the gas 

stream. To determine if the flow is choked, first use Equation 12-2 to determine the critical vessel 

pressure for sonic flow conditions. 

( ) ( )

42.9 psia 2

1.14 1 24.7

2

1 / 1 1.14 / 0.14

⎟ = ⎠

⎞ ⎜

⎝

⎛ + ⎟ = ⎠

⎞ ⎜

⎝

⎛ + ° =

k k −

vessel out

k P P 

The pressure of the vessel is far greater than this, so the flow is choked. Equation 2-4 is used to 

calculate the discharge rate by setting the Mach number is set to 1. Equation 2-4 requires the 

following variables in specific units. 

• MWt: Using propane’s molecular weight of 44 lb/lb-mol for the hydrocarbon portion, the 

average molecular weight of the discharge gas is: 0.5×2 + 0.5×44 = 23 lb/lb-mol. 

• Ci: Using propane as the surrogate for the VOC, the weight fration of VOC is 0.5×44/23 

= 0.9565 weight fraction VOC. 

• A: Valve diameter = 4”/12 = 0.3333 ft. Area = (π/4)×(0.3333)2

 = 0.08725 ft2

• Pvessel: (2050+14.7)/14.7 = 140.5 atm 

• Tvessel: (400 + 273.15)×1.8 = 1,212 °R 

Plugging these values into Equation 2-4 yields: 

( )

2( ) 0.14

4 2.14

4

2

0.14 1

1

4.968 10 1,212

1.14 23 0.9565 0.08725 6.8087 10 140.5

⎟

⎠

⎞ ⎜

⎝

⎛ +

×

× ×

×

Ei = × × × × × 

798,400 4.355 10 0.5962 314 lb/sec 7 = × × × = − Ei

The event occurred for 1,800 sec (30 min ×60 sec/min), so the total release was 565,200 lb or 

283 tons. With a flare efficiency of 98%, the emissions to the atmosphere related to this event was 

5.66 tons VOC [283 × (1-0.98)]. 
Version 2.1.1 

Final ICR Version – Corrected Section 12—Malfunctions/Upsets 

12-6 

12.3 Spills 

Generally, it can be assumed that 100% of the compounds spilled are emitted into the atmosphere. For 

heavier liquids, the mass transfer correlations for an oil layer (Koil) as provided in Appendix B, 

Wastewater Treatment System Equations, Section B.2.1, Oil Water Separators, can be used. Equation 12-

5 can be used to estimate the emissions based on the quantity of material spilled, the area of the spill, and 

the time period from when the initial spill occurred to the final clean up: 

( ) K At V

i i o oil E VC e

/

, 1 − = ρ − (Eq. 12-5) 

where: 

 Ei = Emission estimate of pollutant “i” (kg/spill event) 

ρ = Density of spilled liquid (kg/m3

) 

 V = Volume of spilled material (m3

) 

 Ci,o = Concentration of pollutant “i” in spilled fluid prior to the spill event (mass fraction; 

kg/kg) 

 Koil = Mass transfer coefficient for an oil (organic) liquid (m/sec) 

 t = Duration of the spill (sec) 

 A = Area covered by the spill (m2

). 
Version 2.1.1 

Final ICR Version – Corrected Section 13—References 

13-1 

13. References 

API (American Petroleum Institute). 2002. Refinery Stream Speciation. API Publication No. 4723. 

November 1. 

API (American Petroleum Institute). 2009. Compendium of Greenhouse Gas Emissions Methodologies 

for the Oil and Natural Gas Industry. August 2009. Available at: 

http://www.api.org/ehs/climate/new/upload/2009_GHG_COMPENDIUM.pdf. 

API (American Petroleum Institute) and NPRA (National Petrochemical and Refiners Association). 2010. 

Review of the Emission Estimation Protocol for Petroleum Refineries. Letter to Ms. Brenda 

Shine, U.S. EPA. March 31. 

Bertrand R. R., and J.H. Siegell. 2002. Emission of trace compounds from catalytic cracking regenerators, 

Environmental Progress, 21(3)163-167. October. 

Bertrand R. R., and J.H. Siegell. 2003. Emission of trace compounds from catalytic reforming units, 

Environmental Progress, 22(1)74-77. April. 

Coburn, J. and M. Icenhour. 2008. Memorandum from J. Coburn and M. Icenhour, RTI, to Brenda Shine, 

EPA/SPPD. Preliminary Analysis of Short-term Variability in Storage Vessels Emissions. 

December 29. 

EIA (U.S. Energy Information Administration). 2009. Refinery Capacity Report 2009. Prepared by the 

Energy Information Administration, Washington, DC. June 25. 

EIIP (Emission Inventory Improvement Program). 2007. Methods for Estimating Air Emissions from 

Chemical Manufacturing Facilities. Volume 2, Chapter 16. Prepared by Mitchell Scientific, Inc. 

and RTI International. August. 

EMEP/CORINAIR (European Monitoring and Evaluation Programme/COoRdination of Information on 

AIR emissions). 2006. Atmospheric Emission Inventory Guidebook 2006. Technical Report No. 

11/2006. Available at: http://www.eea.europa.eu/publications/EMEPCORINAIR4. 

ERG (Eastern Research Group, Inc). 2001. Emission Inventory Improvement Program Technical Report 

Series. Volume II, Chapter 2: “Preferred and Alternative Methods for Estimating Air Emissions 

from Boilers.” Prepared for Point Sources Committee Emission Inventory Improvement Program. 

January. 

Hansell, D., and G. England. 1998. Air Toxic Emission Factors for Combustion Sources Using Petroleum 

Based Fuels, Volumes 1 and 2. API Publication 348. Prepared by EER for S. Folwarkow, 

Western States Petroleum Association, Concord, CA, and K. Ritter, American Petroleum 

Institute, Washington, DC. 

Levelton Consultants Ltd. 2005. Emission Monitoring and Reporting Strategy – Summary and 

Background. Prepared for Canadian Council of Ministers of the Environment and NFPRER 

Monitoring and Reporting Team. 

Lev-On, M., Epperson, D., Siegell, J., and Ritter, K. (2007). Derivation of new emission factors for 

quantification of mass emissions when using optical gas imaging for detecting leaks. J Air Waste 

Manag Assoc 57( 9):1061-1070 
Version 2.1.1 

Final ICR Version – Corrected Section 13—References 

13-2 

Lucas, B. 2007. Memorandum from B. Lucas, EPA/SPPD, to Project Docket File (EPA Docket No. EPAHQ-OAR-2003-0146). Storage Vessels: Control Options and Impact Estimates. August 3, 2007. 

Docket Item No. EPA-HQ-OAR-2003-0146-0014. 

NYSERDA (New York State Energy Research and Development Authority). 2005. Hydrogen Fact Sheet. 

Hydrogen Production–Steam Methane Reforming (SMR). Available at: 

http://www.getenergysmart.org/Files/HydrogenEducation/6HydrogenProductionSteamMethaneR

eforming.pdf. 

Potter, T., and K. Simmons. 1998. Composition of Petroleum Mixtures, Volume 2. Total Petroleum 

Hydrocarbon Criteria Working Group Series. University of Massachusetts. Amherst, 

Massachusetts. 

RTI (Research Triangle Institute). 2002. Petroleum Refinery Source Characterization and Emission 

Model for Residual Risk Assessment. Prepared for U.S. Environmental Protection Agency, Office 

of Air Quality Planning and Standards, Research Triangle Park, NC. EPA Contract No. 68-D6-

0014. July. 

SCAQMD (South Coast Air Quality Management District). 2004a. Source Test Report 03-194 Conducted 

at Chevron/Texaco Refinery, El Segundo, California—Volatile Organic Compound (VOC), 

Carbon Monoxide (CO), and Particulate Matter (PM) Emissions from a Coke Drum Steam Vent. 

May 14. 

SCAQMD (South Coast Air Quality Management District). 2004b. Source Test Report 03-197 Conducted 

at Conoco-Phillips Refinery, Carson, California—Volatile Organic Compound (VOC), Carbon 

Monoxide (CO), and Particulate Matter (PM) Emissions From a Coke Drum Steam Vent. July 23. 

SCAQMD (South Coast Air Quality Management District). 2004c. Source Test Report 03-198 Conducted 

at Exxon Mobil Refinery, Torrance, California—Volatile Organic Compound (VOC), Carbon 

Monoxide (CO), and Particulate Matter (PM) Emissions From a Coke Drum Steam Vent. 

March 4. 

SCAQMD (South Coast Air Quality Management District). 2004d. Source Test Report 03-200 Conducted 

at Shell Oil Refinery, Wilmington, California—Volatile Organic Compound (VOC), Carbon 

Monoxide (CO), and Particulate Matter (PM) Emissions From a Coke Drum Steam Vent. July 1. 

TCEQ (Texas Commission on Environmental Quality). 2000. Air Permit Technical Guidance for 

Chemical Sources: Loading Operations. 

TCEQ (Texas Commission on Environmental Quality). 2003. Source Sampling Procedures Manual, 

Appendix P, Cooling Tower Monitoring, Air Stripping Method (Modified El Paso Method) for 

Determination of Volatile Organic Compound Emissions from Water Sources. January 31. 

TCEQ (Texas Commission on Environmental Quality). Air Quality Division. 2009. 2008 Emissions 

Inventory Guidelines. RG-360A/08. January. 

The United States – Mexico Foundation for Science. 2008. A Customized Approach for Quantifying 

Emissions for the Electric Power Generation Sector in Mexico. Prepared for: SEMARNAT and 

CFE. Revision 2, Revised by RTI International for U.S. Environmental Protection Agency Clean 

Air Markets Division and Climate Change Division. December. 

Tumbore, DC. 1998. The magnitude and source of air emissions from asphalt blowing operations. 

Environmental Progress 17(1):53–59. 
Version 2.1.1 

Final ICR Version – Corrected Section 13—References 

13-3 

U.S. EPA (Environmental Protection Agency). 1995a. Compilation of Air Pollutant Emission Factors. 

Volume 1: Stationary Point and Area Sources. AP-42, Fifth Edition. Office of Air Quality 

Planning and Standards, Research Triangle Park, NC. 

U.S. EPA (Environmental Protection Agency). 1995b. Protocol for Equipment Leak Emission Estimates. 

EPA-453/R-95-017. Office of Air Quality Planning and Standards, Research Triangle Park, NC. 

U.S. EPA (Environmental Protection Agency). 1996. Method 8260B, Volatile Organic Compounds by 

Gas Chromatography/Mass Spectrometry. Revision 2, December. SW-846. 

U.S. EPA (Environmental Protection Agency). 1998a. Locating and Estimating Air Emissions from 

Sources of Benzene. EPA-454/R-98-011. Office of Air Quality Planning and Standards, Research 

Triangle Park, NC. 

U.S. EPA (Environmental Protection Agency). 1998b. Petroleum Refineries—Background Information 

for Proposed Standards, Catalytic Cracking (Fluid and Other) Units, Catalytic Reforming Units, 

and Sulfur Recovery Units. EPA-453/R-98-003. Washington, DC: Government Printing Office. 

U.S. EPA (Environmental Protection Agency). 1998c. Study of Hazardous Air Pollutant Emissions from 

Electric Utility Steam Generating Boilers—Final Report to Congress. Volume 1. EPA-453/R-98-

004a. Office of Air Quality Planning and Standards, Research Triangle Park, NC. 

U.S. EPA (Environmental Protection Agency). 2006. TANKS Emissions Estimation Software, Version 

4.09D. Office of Air Quality Planning and Standards, Technology Transfer Network, 

Clearinghouse for Inventories and Emissions Factors, Available at 

http://www.epa.gov/ttn/chief/software/tanks/index.html. 

U.S. EPA (Environmental Protection Agency). 2009. Mandatory Reporting of Greenhouse Gases (Final 

Rule). Federal Register: 74 FR 56260. October 30. 

URS Corporation. 2008. Source Test Report of the Coker Steam Vent. Prepared for Hovensa, LLC, St. 

Croix, U.S. Virgin Islands. September 8. 

Yerushalmi, L., and S.R. Guiot. 1998. Kinetics of biodegradation of gasoline and its hydrocarbon 

constituents. Appl Microbiol Biotechnol 49:475−481. 

 
Version 2.1.1 

Final ICR Version – Corrected Section 13—References 

13-4 

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Final ICR Version – Corrected Appendix A—Average Stream Compositions 

A-1 

Appendix A 

Average Stream Compositions 
Version 2.1.1 

Final ICR Version – Corrected Appendix A—Average Stream Compositions 

A-2 

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Version 2.1.1 

Final ICR Version – Corrected Appendix A—Average Stream Compositions 

A-3 

Table A-1. Refinery Average Stream Hazardous Air Pollutant Compositions—Default Values 

Average Weight Percent of Compound in Process Unit Streama

1,3-Butadiene 

106-99-0 

n-Hexane 

 110-54-3 

2,2,4-Trimethyl 

pentane 

540-84-1 

Benzene 

71-43-2 

Toluene 

108-88-3 

Xylenes (total) 

1330-20-7 

Ethylbenzene 

100-41-4 

Cumene 

98-82-8 

1,2,4-trimethyl 

benzeneb

95-63-6 

Naphthalene 

91-20-3 

Biphenyl 

92-52-4 

Styrene 

100-42-5

Process Units 

Atmospheric Distillation 0.01 4.28 0.05 0.86 1.7 1.97 0.63 0.12 0.63 0.25 0.06 0.001

Vacuum Distillation - 0.007 0.004 0.004 0.043 0.020 0.024 0.001 0.020 0.12 0.09 - 

Coking Unit 0.04 2.49 0.75 0.42 1.30 1.76 0.70 0.12 0.70 0.28 0.001 0.19

Cat Hydrocracker 0.03 1.86 1.04 1.27 2.72 2.67 1.02 0.09 1.33 0.20 0.001 0.19

FCCU 0.01 0.99 0.29 1.03 3.28 4.90 1.07 0.10 1.92 0.72 0.43 0.14

CRU 0.009 2.75 0.25 6.34 17.44 17.61 3.88 0.42 5.93 0.87 0.001 0.11

Hydrodesulfurization - 1.89 0.0001 0.37 1.72 1.94 0.37 0.07 0.40 0.25 0.22 - 

Alkylation 0.22 1.57 25.24 0.03 2.05 0.08 5.0E-5 5.0E-5 5.0E-5 5.0E-5 5.0E-5 0.02

Isomerization - 3.22 0.01 0.51 0.64 0.15 - - - - - - 

Polymerization - 0.54 0.73 1.24 1.76 1.18 0.09 - - - - 

Products 

Aromatics Extract - 

Benzene - - - 99.99 0.009 0.002 - - - - - - 

Aromatics Extract - 

Toluene - - - 0.296 95.61 3.49 2.82 - 0.3 - - - 

Aromatics Extract - 

Xylenes - - - - - 77.89 16.08 0.59 - - - - 

Aromatics Extract - 

Heavy Aromatics - - - 5.7 19.36 25.03 3.56 0.965 4.94 0.314 - - 

Commercial Jet Fuel - 1.68 0.0006 0.577 0.965 1.22 0.257 0.106 0.815 0.627 0.409 - 

Conventional Gasoline 0.0009 2.22 2.94 1.4c 7.75 6.56 1.490 0.219 3.002 0.415 - 0.0767

Aviation Gasoline - 2.30 - 1.01 7.69 3.37 1.2 0.103 0.5 0.695 - - 

Reformulated Gasoline - 1.36 1.10 0.8b 7 7.31 1.26 0.19 2.52 0.21 - - 

Diesel Fuel - 0.030 0.007 0.004 0.081 0.241 0.053 0.056 0.349 0.285 0.117 - 

Home Heating Oil - - - - 0.108 0.300 0.095 - 0.429 0.453 0.181 - 

Solvent-refined Lubes - - - - - - - - - - - - 

Crude Oil 

9.81E05 1.341 0.185 0.312 0.542 0.811 0.186 0.108 0.377 0.139 0.030 

 

a

 Based on Petroleum Environmental Research Forum (PERF) refinery process stream speciation study (API, 2002), 

unless otherwise specified. 

b

 1,2,4-Trimethylbenzene is not a HAP, but it is a prevalent VOC in many refinery streams. c

 Average benzene content of conventional and reformulated gasoline based on Fuel Trends Resport: Gasoline 

1995-2005 (U.S. EPA. Report No. EPA420-R-08-002. January 2008), corrected to weight percent using the 

density correction factor of 0.876/0.739 (i.e., 1.16vol%×0.876/0.739 = 1.4wt%; 0.67vol%×0.876/0.739 = 0.8wt%). 
Version 2.1.1 

Final ICR Version – Corrected Appendix A—Average Stream Compositions 

A-4 

Property Calculations 

If the weight composition of a commodity is available but other property data are not, estimates can be 

made. For example, if the liquid component mixture and the weight fraction for gasoline are known, then 

the vapor pressure of the liquid, the MW of vapor, and the weight fraction of the vapor can be estimated. 

The following steps and equations may be used for calculating these estimates: 

1. From the weight fraction values in the gasoline (liquid), Equation A-1 should be used to estimate 

the number of moles of component “i.” 

i

i

i MW

Wtfrac

n = (Eq. A-1) 

2. From moles of component “i” (liquid), Equation A-2 should be used to estimate the mole fraction 

of component “i” (liquid). 

T

i

i

n

n

x = (Eq. A-2) 

3. Equation A-3 should be used to calculate the partial pressure of each component “i” in liquid. 

 P(i) = P × xi (Eq. A-3) 

where: 

 P(i) = Partial pressure of component “i” (psia) 

 P = Vapor pressure of pure component “i” at the liquid temperature (psia) 

 xi = Liquid mole fraction 

4. To estimate the total pressure of the liquid, Equation A-4 should be used to estimate the average 

vapor pressure for the gasoline mixture by summing the partial pressure of each component “i” 

(liquid). 

= ∑

n

PtotalVP Pi

1

 (Eq. A-4) 

5. From mole fraction of component “i” (liquid), Equation A-5 should be used to estimate the mole 

fraction of component “i” in the vapor using Raoult’s law. 

totalVP

i

i P

P

y = (Eq. A-5) 

6. Equation A-6 should be used to estimate the MW of the gasoline vapor, MWVAP, using the mole 

fraction of vapor (yi) and the MW of the pure component “i”(MWi). 

= ∑ ×

n

Vap i MWi MW y

1

 (Eq. A-6) 

where: 

 MWVAP = Molecular weight of the vapor (lb/mol) 

 MWi = Molecular weight of component “i” (lb/mol) 
Version 2.1.1 

Final ICR Version – Corrected Appendix A—Average Stream Compositions 

A-5 

7. Equation A-7 should be used to estimate the gasoline vapor weight fractions using the gasoline 

vapor mole fractions and the MWVAP. 

Vap

i i

vap MW

y MW Wtfrac× = (Eq. A-7) 

Example A-1: Calculation of Vapor Pressure and Molecular Weight for Reformulated 

Gasoline Loading Example 

Calculate the vapor pressure of gasoline and MWVAP for submerged loading of reformulated 

gasoline into dedicated-service gasoline transport tank trucks (each with a volume of 8,000 

gallons) based on the following information: 

The refinery loads 100 tank trucks per year at a bulk temperature of 77°F. Property data are 

available for liquid composition of the gasoline only and are provided in Table A-2. 

First, the vapor pressure for each constituent is determined at the loading temperature using 

Antoine’s equation and Antoine’s coefficients, such as those provided in Table 7.1-5 of AP-42 

(U.S. EPA, 1995a). 

Using Steps 1 through 7 from this Appendix A, the gasoline liquid mole fraction can be 

calculated from the weight fraction or weight percent component composition, the partial 

pressure of each component in liquid, and the gasoline vapor mole fraction using Raoult’s law 

(see each calculation “step” in the columns in Table A-2). 

 Step 1. 

i

i

i MW

Wtfrac

n =

 Step 2. 

T

i

i

n

n

x =

 Step 3. i P(i) = P × x

 Step 4. = ∑

n

PtotalVP Pi

1

 Step 5. 

totalVP

i

i P

P

y =

 Step 6. = ∑ ×

n

Vap i MWi MW y

1

 Step 7. 

Vap

i i

vap MW

y MW wtfrac× =

See Table A-2 for the calculations of thee variables. At 77°F, the total system vapor pressure is 

4.77 psia and the MW of the vapor, MWGasolineVAP, is 67.4 lb/lb-mol. 
Version 2.1.1 

Final ICR Version – Corrected Appendix A—Avera

A-6 

Table A-2. Sample Calculation of Average Molecular Weight and Vapor Weight Fractiona

Step 1 Step 2 Step 3 Step 4 Step 5 

A B C D=C/A E=D/(ΣD) F=E*B G=F/(ΣF) 

CAS 

Number Compound MolWt 

Pvap at 

77°F (psia)

Gasoline 

Liquid 

(wt%) 

Gasoline 

Liquid 

(moles/100 

g) 

Gasoline 

Liquid 

(mole 

fraction) 

Gasoline 

Partial 

Pressure 

(psia) 

Gasoline 

Vapor 

(mole 

fraction) 

C

V

71-43-2 Benzene 78.11 1.840 0.80 1.02E-04 9.36E-03 1.72E-02 3.61E-03 

110-54-3 Hexane 86.18 2.928 1.36 1.58E-04 1.44E-02 4.22E-02 8.85E-03 108-88-3 Toluene 92.14 0.550 7.0 7.60E-04 6.94E-02 3.82E-02 8.01E-03 

1330-20-7 Xylene 106.14 0.169 7.31 6.89E-04 6.30E-02 1.07E-02 2.23E-03 

100-41-4 Ethylbenzene 106.17 0.184 1.26 1.19E-04 1.08E-02 1.99E-03 4.18E-04 540-84-1 2,2,4-Trimethylpentane 114.23 0.954 1.098 9.61E-05 8.79E-03 8.38E-03 1.76E-03 

98-82-8 Cumene 120.19 0.089 0.19 1.58E-05 1.44E-03 1.28E-04 2.68E-05 91-20-3 Naphthalene 128.17 0.005 0.21 1.64E-05 1.50E-03 7.63E-06 1.60E-06 

106-97-8 n-Butane 58.12 35.220 4.7 8.09E-04 7.39E-02 2.60E+00 5.46E-01 

72-28-5 Isobutane 58.12 13.294 1.7 2.92E-04 2.67E-02 3.55E-01 7.45E-02 

109-66-0 Pentane 72.15 10.285 3.9 5.41E-04 4.94E-02 5.08E-01 1.07E-01 

78-78-4 Isopentane 72.15 3.670 7.9 1.09E-03 1.00E-01 3.67E-01 7.70E-02 

 C6 surrogate 86.18 4.094 10.08 1.17E-03 1.07E-01 4.38E-01 9.18E-02 

C7 surrogate 100.2 1.274 7.21 7.20E-04 6.58E-02 8.38E-02 1.76E-02 

 C8 surrogate 114.23 0.522 3.21 2.81E-04 2.57E-02 1.34E-02 2.81E-03  C9 surrogate 120.19 0.039 7.29 6.07E-04 5.54E-02 2.18E-03 4.57E-04 

Other VOC 100.20 0.884 34.78 3.47E-03 3.17E-01 2.80E-01 5.88E-02 

nT PtotalVP 

Total 100 0.0109 1.00 4.77 1.00 

a Weight percents for HAP based on composition provided in Table A-1; weight percent VOC from n-butane to C9 surrogate are based 

Petroleum Mixtures, Volume 2 of the Total Hydrocabon Criteria Working Group Series. Prepared by T.L. Potter and K.E. Simmons. MISBN 1-844-940-19-6; n-Heptane was used as the surrogate for the remaining uncharacterized fraction of the liquid gasoline (“other Vuse facility-specific data for light VOC (C4 to C6 compounds) concentrations because these significantly impact the calculated vapor-p
Version 2.1.1 

Final ICR Version – Corrected Appendix B—Wastewater Treatment System Equations 

B-1 

Appendix B 

Wastewater Treatment System Equations 
Version 2.1.1 

Final ICR Version – Corrected Appendix B—Wastewater Treatment System Equations 

B-2 

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Version 2.1.1 

Final ICR Version – Corrected Appendix B—Wastewater Treatment System Equations 

B-3 

B. Wastewater Treatment System Equations 

This appendix provides a brief presentation of the key equations needed to calculate air emissions from 

typical wastewater treatment units. The purpose of this appendix is to document the equations used in the 

simplified refinery wastewater emission tool and to correct errors found in the presentation of some of 

these equations as provided in Chapter 4.3 of AP-42 (EPA, 1995). 

B.1 Mass Transfer Rate Equations 

The overall mass transfer coefficient that determines the rate of volatilization is determined based on a 

two-resistance module: a liquid phase mass transfer resistance and a gas phase mass transfer resistance. 

The liquid and gas phase mass transfer resistances are very different for turbulent surfaces compared to 

quiescent (laminar flow) surfaces. Therefore, the overall mass transfer coefficient is a composite of the 

overall mass transfer coefficient for the turbulent surface area and the overall mass transfer coefficient for 

the quiescent surface area based on an area weighted average as follows: 

A

K A K A

K OL t t OL q q

OL

× + × = , , (Eq. B-1) 

where: 

 KOL = Overall mass transfer coefficient (m/s) 

 KOL,t = Overall mass transfer coefficient for turbulent surface areas (m/s) 

 At = Turbulent surface area = faer A, m2

 faer = Fraction of total surface area affected by aeration 

 KOL,q = Overall mass transfer coefficient for quiescent surface areas (m/s) 

 Aq = Quiescent surface area = (1-faer) A, m2

 (Note: At + Aq must equal A) 

 A = Total surface area (m2

) 

The overall mass transfer coefficient for turbulent surface areas based on the two resistance module is: 

1

, ,

,

1 1 −

⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

′× = +

l t g t

OL t k H k

K (Eq. B-2) 

where: 

 kl,t = liquid phase mass transfer coefficient for turbulent surface areas (m/s) 

 H' = dimensionless Henry's law constant = H/RTH

 H = Henry's law constant (atm-m3

/mol) 

 R = ideal gas law constant = 0.00008205 (atm-m3

/mol-K) 

 TH = temperature at which Henry's law constant was evaluated = 298 K. 

 kg,t = gas phase mass transfer coefficient for turbulent surface areas (m/s) 

Similarly, the overall mass transfer coefficient for quiescent surface areas is 

1

, ,

,

1 1 −

⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

′× = +

l q g q

OL q k H k

K (Eq. B-3) 

where: 

 kl,q = Liquid phase mass transfer coefficient for quiescent surface areas (m/s) 

 kg,q = Gas phase mass transfer coefficient for quiescent surface areas (m/s). 
Version 2.1.1 

Final ICR Version – Corrected Appendix B—Wastewater Treatment System Equations 

B-4 

The mass transfer correlations used in this module to estimate the individual mass transfer coefficients are 

the same as those used in the WATER9 emission model developed by EPA. The documentation of these 

mass transfer correlations can be accessed from EPA’s Web site at 

http://www.epa.gov/ttn/chief/software/water/index.html. Only the basic equations are provided here. For a 

more detailed discussion of these mass transfer correlations, the reader is referred to Chapter 5 of the Air 

Emissions Models for Waste and Wastewater report (U.S. EPA, 1994). 

B.1.1 Liquid Phase Mass Transfer Coefficient for Turbulent Surfaces 

The liquid phase, turbulent surface mass transfer coefficient is calculated as follows: 

( ) 0.5

2,

,

3 20

, 10.76

8.22 10 1.024

⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

× ×

× × × × × × =

− −

O l

i l

t l

cf l

T

tot

l t D

D

A

J P O MW

k

ρ

 (Eq. B-4) 

where: 

 J = Oxygen transfer factor (lb/h/hp) 

 Ptot = Total power to the impellers (hp) 

 T = Water temperature in (°C) 

 Ocf = Oxygen correction factor 

 MWl = Molecular weight of liquid (water) (g/mol) 

ρl = Density of liquid (water) (g/cm3

 = Mg/m3) 

 Di,l = Diffusivity in liquid (water) (cm2

/s) 

 DO2,l = Diffusivity of oxygen in liquid (water) (cm2

/s) 

B.1.2 Gas Phase Mass Transfer Coefficient for Turbulent Surfaces 

The gas phase, turbulent surface mass transfer coefficient is calculated as follows: 

1

.

7 1.42 0.4 0.5 0.21

, 1.35 10 Re − − −

g t = × ×g

× p × Scg× Fr × Di a × MWa × dimp k (Eq. B-5) 

where: 

 Reg = Gas phase Reynolds number = (dimp

2

 w ρg)/μg

ρg = Density of gas (air) (g/cm3

) 

μg = Viscosity of gas (air) (g/cm-s) 

 p = Power number = 0.85 (550 Ptot/Naer) gc,2 / [(62.428ρl )w3

 (dimp/30.48)5 ] 

 gc,2 = Gravitational constant = 32.17 lbm-ft/s2

-lbf = 0.03283 gc

 Naer = Number of aerators 

 w = Rotational speed (rad/s) 

 Scg = Gas phase Schmidt number = μg/(ρg Di,a) 

 Fr = Froud number = [w2

 (dimp/30.48) ]/ gc,2

 Di,a = Diffusivity of constituent in air (cm2

/s) 

 MWa = Molecular weight of air (g/mol) 

 dimp = Impeller diameter (cm) 

 gc = Gravitational constant = 980 cm/s2
Version 2.1.1 

Final ICR Version – Corrected Appendix B—Wastewater Treatment System Equations 

B-5 

B.1.3 Liquid Phase Mass Transfer Coefficient for Quiescent Surfaces 

The appropriate correlation to use to estimate the liquid phase mass transfer coefficient is dependent on 

the wind speed and the fetch-to-depth ratio of the impoundment. The fetch is the linear distance across the 

treatment unit, and it is calculated from the unit’s surface area, assuming a circular shape. That is, 

0.5

4 ⎟

⎠

⎞ ⎜

⎝

⎛ = π

A F (Eq. B-6) 

where: 

 F = Fetch (m) 

For wind speeds less than 3.25 m/s, the following correlation is used regardless of the fetch-to-depth ratio 

(F/dliq): 

3

2

6 ,

, 2.78 10 ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛ = × −

ether

i l

l q D

D

k (Eq. B-7) 

where: 

 kl,q = Liquid phase, quiescent surface mass transfer coefficient (m/s) 

 Di,l = Diffusivity of constituent in liquid (water) (cm2

/s) 

 Dether = Diffusivity of ether in water = 8.5 × 10-6 cm2

/s 

For windspeeds greater than or equal to 3.25 m/s, the appropriate correlation is dependent on the fetch-todepth ratio as follows: 

( )( ) 6 4 * 0.5

, 14, 1.0 10 10 − − − < = × + × liq

b

l q

liq

k a U Sc

d

F For (Eq. B-8) 

where: 

 a = Equation constant, a = 34.1 for U* > 0.3 m/s; a = 144 for U* < 0.3 m/s 

 U*

 = Friction velocity, m/s = 0.01U (6.1 + 0.63U)0.5

 U = Wind speed at 10 m above the liquid surface 

 b = Equation constant, b = 1 for U* > 0.3 m/s; b = 2.2 for U* < 0.3 m/s 

 Scliq = Liquid phase Schmidt number = μl/(ρl Di,l) 

μl = Viscosity of water (g/cm-s) 

ρl = Density of water (g/cm3

) 

3

2

9 7 2 , 14 51.2, , 2.605 10 1.277 10 ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

⎥

⎥

⎦

⎤

⎢

⎢

⎣

⎡

+ × ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

≤ ≤ = × − −

ether

i l

liq

l q

liq D

D

U

d

F k

d

F For (Eq. B-9) 

3

2

7 2 , 51.2, , 2.611 10 ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

> = × −

ether

i l

l q

liq D

D

k U

d

F For (Eq. B-10) 
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B-6 

B.1.4 Gas Phase Mass Transfer Coefficient for Quiescent Surfaces 

The gas phase mass transfer coefficient for quiescent surface areas is estimated as follows: 

3 0.78 0.67 0.11

, 4.82 10− − − k g q = × ×U × Scg

× F (Eq. B-11) 

B.2 Collection Systems and Process Units 

The fraction emitted (fe) values for the collection system components are based on the models described 

in the EPA document titled Industrial Wastewater Volatile Organic Compound Emissions (U.S. EPA, 

1990). Briefly, the correlation between the fraction emitted (fe) and Henry’s law constant were 

determined. The correlation equations were then used to determine the emissions for each compound and 

uncontrolled collection system component. 

Table B-1. Model Collection System Components and fe–Henry’s Law Correlation 

Collection System Component Correlation 

Drains fe=0.035*ln(HLC)+0.4079 

Trenches fe=0.005*ln(HLC)+0.0658 

Manholes fe=0.009*ln(HLC)+0.1036 

Junction Boxes fe=0.0105*ln(HLC)+0.1416 

Lift Stations fe=0.0312*ln(HLC)+0.4163 

Sumps fe=0.0004*ln(HLC)+0.007 

B.2.1 Junction Boxes and Lift Stations 

Junction boxes and lift stations collect and equalize wastewater prior to pumping to the wastewater 

treatment system. As previously mentioned, these components should be covered the vented; however, if 

uncovered, the following procedure can be used to estimate air emissions: 

 Step 1: Calculate the liquid phase mass transfer coefficient for turbulent surfaces (kl,t) with 

Equation B-4. Alternatively, a simplified version specifically for junction boxes and lift stations 

that is based on default values presented in AP-42 yields: 

( )

⎥

⎥

⎦

⎤

⎢

⎢

⎣

⎡

=

−

t

i l

T

l t A

V D

k

0.5

,

( 20)

,

0.184 1.024

 (Eq. B-12) 

where: 

 V = Unit volume (m3

) 

Default values: 

 J = 3 (lb/h/hp) 

 Ocf = 0.83 

 MWl = 18 (g/mol) 

 ρl = 1 (g/m3

) 

 Ptot = 0.0264 (hp/m3

) ×V 

 DO2,l = 2.4×10-5 (cm2

/s) 

 Step 2: Calculate the gas phase mass transfer coefficient for quiescent surfaces (kg,q) as described 

in Section B.1.4, Gas Phase Mass Transfer Coefficient for Quiescent Surfaces. 
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Final ICR Version – Corrected Appendix B—Wastewater Treatment System Equations 

B-7 

 Step 3: Calculate the overall mass transfer coefficient (K) with the following equation: 

( )

( ) g q l t

l t g q

OL H k k

k H k

K

, ,

, ,

'

'

+ = (Eq. B-13) 

 Step 4: Calculate the tank effluent concentration (CL) with the following equation: 

( ) K A Q

QC C g m

OL

L

+ = 3 0 ( / ) (Eq. B-14) 

 Step 5: Calculate the air emissions (N) with the following equation: 

N(g /s) = KOLCL A (Eq. B-15) 

B.2.2 Sumps 

Sumps typically collect and equalize wastewater from various collection systems prior to treatment. As 

previously mentioned, these components should be covered the vented; however, if uncovered, the 

following procedure can be used to estimate air emissions: 

 Step 1: Calculate the liquid phase mass transfer coefficient for quiescent surfaces (kl,q) as 

described in Section B.1.3, Liquid Phase Mass Transfer Coefficient for Quiescent Surfaces. 

 Step 2: Calculate the gas phase mass transfer coefficient for quiescent surfaces (kg,q) as described 

in Section B.1.4, Gas Phase Mass Transfer Coefficient for Quiescent Surfaces. 

 Step 3: Calculate the overall mass transfer coefficient (K) with the following equation: 

( )

( ) g q l q

l q g q

OL H k k

k H k

K

, ,

, ,

'

'

+ = (Eq. B-16) 

 Step 4: Calculate the tank effluent concentration (CL) with using Equation B-14: 

 

 Step 5: Calculate the air emissions (N) with using Equation B-15: 

 

B.2.3 Weirs 

Weirs are typically used in wastewater collection and treatment units as dams, allowing solids to settle in 

the quiescent areas. The liquid phase mass transfer coefficients (kl) is determined by Equations B-17a and 

17b. The gas phase mass transfer coefficients (kg) is determined using Equation B-18. These liquid and 

gas phase mass transfer coefficient equations are based on the work presented by Nakasone (1987) and 

Pincince (1991). Air emissions (N) for each pollutant are calculated using equation B-20. 

 (Eq. B-17a) 

 (Eq. B-17b) 

 (Eq. B-18) 

 (Eq. B-19) 

 (Eq. B-20) 
Version 2.1.1 

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B-8 

where: 

 Q = Volumetric flow rate (m3

/s) 

 Co = Initial constituent concentration (g/m3

) 

 h = Weir height (ft) 

 r = oxygen deficit ratio 

 q = hydraulic weir loading [m3

/(m·h)] 

 Z = tailwater depth (m) 

 kl = liquid-phase mass transfer coefficient (m/s) 

 Dlv = diffusion coefficient for the organic in water (cm2

/s) 

 Dlo = diffusion coefficient for air in water (cm2

/s) 

 kg = gas-phase mass transfer coefficient (m/s) 

 Dgv = diffusion coefficient of the organic in air (cm2

/s) 

 Dgo = diffusion coefficient of the reference material in air (cm2/s) 

 Ko = overall mass transfer coefficient (m/s) 

 K = partition coefficient (atm-m3

/mol) 

 N = air emissions (g/s). 

B.2.4 Oil-Water Separators (API) 

An oil-water separator is a treatment unit designed to separate oil and suspended solids from wastewater. 

As previously mentioned, these units are typically covered and vented and thus open-air emission 

estimations are not required. However, if the treatment units are uncovered, then the following procedure 

can be used to estimate air emissions. 

First, calculate the gas phase mass transfer coefficient for quiescent surfaces (kg,q) with Equation B-11. 

Next, calculate the overall mass transfer coefficient for oil (Koil) with the following equations: 

oil g qKeqoil K k = , (Eq. B-21) 

where: 

oil a o

a oil

oil MW P

P MW Keq

ρ

ρ*

= (Eq. B-22) 

Air emissions are determined from the following equations: 

N(g /s) = KoilCL,oil A (Eq. B-23) 

where: 

( )

oil oil

oil oil

L oil K A Q

Q Co C g m

+ = 3

, / (Eq. B-24) 

If the oil layer is > 1cm, then use this equation: 

[ ] oil oil ow

ow

oil f f K

K Co Co − + = 1 (Eq. B-25) 
Version 2.1.1 

Final ICR Version – Corrected Appendix B—Wastewater Treatment System Equations 

B-9 

If the oil layer is < 1cm, then use this equation: 

oil

oil f

Co Co = (Eq. B-26) 

Qoil = f oilQ (Eq. B-27) 

where: 

 P* = Constituent vapor pressure (mm Hg) 

 MWoil = Molecular weight of oil (g/mol) 

ρoil = Density of oil (g/m3

) 

 P0 = Total pressure (atm) 

 Qoil = Volumetric flow rate of oil (m3

/s) 

 Cooil = Initial concentration of constituent in oil phase (g/m3

) 

 Kow = Octanol-water partition coefficient 

 foil = Fraction of volume that is oil 

B.2.5 Dissolved Air Flotation 

DAF is a wastewater treatment unit that clarifies water by removing suspended oil and solids by bubble 

flotation. As previously mentioned, these treatment units are typically covered and vented to control 

devices. However, if the treatment units are uncovered, then the following procedure can be followed to 

estimate air emissions. 

First, the liquid phase mass transfer coefficient for quiescent surfaces (kl,q) can be determined by the 

method described in Section B.1.3, Liquid Phase Mass Transfer Coefficient for Quiescent Surfaces. 

Second, the gas phase mass transfer coefficient for quiescent surface (kg,q) can be calculated by the 

method described in Section B.1.4. Third, the overall mass transfer coefficient (KOL) can be determined 

by Equation B-1. Finally, the air emissions (N) can be calculated with the following equations: 

( ) KOL A QaH CL N(g /s) = + ′ (Eq. B-28) 

where: 

( ) K A Q Q H

QC C g m

OL a

L

+ + ′ = 3 0 ( / ) (Eq. B-29) 

B.2.6 Equalization Tanks (Mixed Tank with No Biodegradation) 

Equalization tanks dampen variations in wastewater flow rate and pollutant load to lessen negative 

impacts on downstream processes. As previously mentioned, these tanks should be covered the vented; 

however, if these tanks are uncovered, then the following procedure can be used to estimate air emissions: 

 Step 1: Calculate the liquid phase mass transfer coefficient for turbulent surfaces (kl,t) with 

Equation B-4. 

 Step 2: Calculate the gas phase mass transfer coefficient for turbulent surfaces (kg,t) with Equation 

B-5. 

 Step 3: Calculate the liquid phase mass transfer coefficient for quiescent surfaces (kl,q) as 

described in Section B.1.3, Liquid Phase Mass Transfer Coefficient for Quiescent Surfaces. 

 Step 4: Calculate the gas phase mass transfer coefficient for quiescent surfaces (kg,q) as described 

in Section B.1.4, Gas Phase Mass Transfer Coefficient for Quiescent Surfaces. 
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Final ICR Version – Corrected Appendix B—Wastewater Treatment System Equations 

B-10 

 Step 5: Calculate the overall mass transfer coefficient for turbulent surfaces (KOL,t) with Equation 

B-2. 

 Step 6: Calculate the overall mass transfer coefficient for quiescent surfaces (KOL,q) with Equation 

B-3. 

 Step 7: Calculate the overall mass transfer coefficient (KOL) with Equation B-1. 

 Step 8: Calculate the tank effluent concentration (CL) with the following equation: 

( ) K A Q

QC C g m

OL

L

+ = 3 0 ( / ) (Eq. B-30) 

 Step 9: Calculate the air emissions (N) with the following equation: 

N(g /s) = KOLCL A (Eq. B-31) 

B.2.7 Biological Treatment Unit (with a Known Wasting Rate) 

The determination of air emissions from biological treatment units is similar to equalization tanks with 

the addition of a biodegradation factor. Additionally, whereas turbulent and quiescent surface areas 

impact air emissions for mechanically aerated systems, the air volumetric flow rate impacts diffused 

aeration systems. Consequently, two slightly different methods are used to estimate air emissions. 

For mechanically aerated systems, follow Steps 1 through 7 of Section B.2.5 to determine the overall 

mass transfer coefficient (KOL). 

For diffused aeration systems, first calculate the average diffused air flow rate Qa,avg (m3

/s): 

2

0

,

⎥

⎦

⎤ ⎢

⎣

⎡

+

=

a

a g

a avg

Q P

Q P

Q (Eq. B-32) 

where: 

 Pg = Blow gauge pressure (lb/in2

) 

 P0 = Atmospheric pressure (atm) × 14.696 (lb/in2

atm)=(lb/in2) 

Monteith et al. (1996) reported the effect of turbulence, induced by diffused bubble aeration, on mass 

transfer at the water surface. Correlations between the mass transfer of ammonia and VOCs were 

established and used to determine KL[NH4]a, kl,ta and kg,ta with the following equations: 

0.4

,

[ 4] 0.08 0.012 ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛ = +

t

a avg

L NH A

Q K a (Eq. B-33) 

where: 

 KL[NH4]a = Ammonium volumetric mass transfer coefficient (h-1) 

Note: make sure the units used are consistent (e.g., Q=m3

/hr and A=m2) 

0.5

, 4

,

, [ 4] ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛ =

l NH

i l

l t L NH D

D

k a K a (Eq. B-34) 
Version 2.1.1 

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B-11 

where: 

 Dl,NH4 = Diffusivity of Ammonium in water (6.93×10-5 cm2

/s) 

 kl,ta = Volumetric liquid phase mass transfer coefficient (hr-1) 

The kl,t values must then be calculated from the kl,ta value with the following equation: 

a

k a

k l t

l t 3600

,

, = (Eq. B-35) 

where: 

 kl,t = Liquid phase mass transfer coefficient (m/s) 

 a = Specific interfacial area based on liquid volume (m-1) = A/V 

 V = Aeration basin volume (m3

) 

Note: kl,t (m/hr) divided by 3600 (s/hr) = (m/s) 

Hsieh et al. (1992) reported the ratio of kg/kl ranged from 2.2 to 3.6 for diffused aeration systems. 

Therefore, kg can be approximated by the following equation: 

g t l t k k , = 3 , (Eq. B-36) 

where: 

 kg,t = Gas phase mass transfer coefficient (m/s) 

The KOL,t, KOL,q, and KOL are then calculated by using steps by using equations B-2, B-3, and B-1. 

Next, calculate the tank effluent concentration (CL) and the emission rate (N) with the following 

equations. 

For mechanically aerated systems: 

N(g /s) = KOLCL A (Eq. B-37) 

For diffused aeration systems: 

( ) ( ) KOL A QaH CL N g /s = + ′ (Eq. B-38) 

where: 

( ) [ ( ) ]

a

b b ac CL g m

2

4 /

0.5 2

3 − + − = (Eq. B-39) 

For mechanically aerated systems: 

i

OL w abs WAS VSS e

Q

K A Q k C Q

a

+ + = , (Eq. B-40) 

( ) 0

max

, C

Q

V C V K A Q k C Q Q

Ks b

i

MLVSS

OL w abs WAS VSS e

i

= + + + − (Eq. B-41) 
Version 2.1.1 

Final ICR Version – Corrected Appendix B—Wastewater Treatment System Equations 

B-12 

For diffused aerated systems: 

i

OL a avg w abs WAS VSS e

Q

K A Q H Q k C Q

a

+ ′ + + = , , (Eq. B-42) 

( ) 0

max

, , C

Q

V C V K A Q H Q k C Q Q

Ks b

i

MLVSS

OL a avg w abs WAS VSS e

i

= + ′ + + + − (Eq. B-43) 

K C0 c = − S (Eq. B-44) 

where: 

 Qw = Wasted activated sludge flow rate (m3

/s) 

 Qe = Effluent flow rate (m3

/s) 

 Qi = Influent flow rate (m3

/s) 

 KS = Half saturation biorate constant (g/m3) 

 Vmax = Maximum biorate constant (g/s-g biomass) 

 CMLVSS = Mixed-liquor volatile suspended solids (g/m3

) 

 CWAS,VSS = Wasted sludge volatile suspended solids (g/m3

) 

 kabs = Partition coefficient for organic contaminant (m3

/g) 

where: 

abs OC KOC k f 6 1 10− = × (Eq. B-45) 

 fOC = Weight fraction of carbon in biomass (g C/g) (default value 0.33) 

 KOC = Organic carbon partition coefficient (g/MgC/(g/ m-3) 

 1×10-6 = unit conversion (megagrams per gram, Mg/g) 

where: 

log KOC = log KOW − 0.32 (Eq. B-46) 

B.2.8 Biological Treatment Unit (with an Unknown Wasting Rate) 

Air emission estimate calculations from aerated lagoons are very similar to those for activated sludge 

units. The difference is sludge is not wasted from the lagoon, rather it settles and accumulates on the 

lagoon bottom until dredging. The assumptions made in this document are: (1) at steady-state conditions 

the amount of sludge that settles and thus removed from the unit is equal to the biomass production rate, 

and (2) once the sludge and associated contaminants settle, they are considered removed from the system. 

Follow the procedure in Section B.2.6 to determine the overall mass transfer coefficient (KOL), the unit 

effluent concentration (CL), and the emission rate (N). However, variables a, b, and c are determined by 

the following equations 

For mechanically aerated systems: 

i

OL BODi i abs e

Q

K A C Q k Q

a

+ + = 0.67

 (Eq. B-47) 

( ) 0

max 0.67 C

Q

V C V K A C Q k Q Q

Ks b

i

MLVSS

OL BODi i abs e

i

= + + + − (Eq. B-48) 
Version 2.1.1 

Final ICR Version – Corrected Appendix B—Wastewater Treatment System Equations 

B-13 

For diffused aerated system: 

i

OL a avg BODi i abs

Q

K A Q H C Q k

a

+ , ′ + 0.67 = (Eq. B-49) 

( ) 0

max

, 0.67 C

Q

V C V K A Q H C Q k

Q

Ks b

i

MLVSS

OL a avg BODi i abs

i

= + ′ + + − (Eq. B-50) 

K C0 c = − S (Eq. B-51) 

B.3 References 

Hsieh, C., R. Babcock, and M. Stenstrom. 1992. Estimating semi-volatile organic compound emission 

rates and oxygen transfer coefficients in diffused aeration. Presented at the 65th Water 

Environment Federation Conference, New Orleans, LA, September 20–24. 

Monteith, H., W. Parker, and H. Melcer. 1996. Impact of bubble-induced surface turbulence on gas-liquid 

mass transfer in diffused aeration systems. Presented at the Water Environment Federation’s 

Annual Technical Exhibition and Conference, Dallas, TX, October 5–9. 

Nakasone, H. 1987. Study of aeration at weirs and cascades. J. Environ. Eng.113:64. 

Pincince, A.B. 1991. Transfer of oxygen and emissions of volatile organic compounds at clarifier weirs. 

Res. J. Water Pollut. Control Fed., 63, 114-119. 

U.S. EPA (Environmental Protection Agency). 1990. Industrial Wastewater Volatile Organic Compound 

Emissions—Background Information for BACT/LAER Determinations. EPA 450/3-90-004. Office 

of Air Quality Planning and Standards, Research Triangle Park, NC. January. 

U.S. EPA (Environmental Protection Agency). 1994. Air Emissions Models for Waste and Wastewater. 

EPA-453/R-94-080A. Office of Air Quality Planning and Standards, Research Triangle Park, NC. 

U.S. EPA (Environmental Protection Agency). 1995. Compilation of Air Pollutant Emission Factors. 

Volume 1: Stationary Point and Area Sources. AP-42, Fifth Edition. Office of Air Quality 

Planning and Standards, Research Triangle Park, NC. 
Version 2.1.1 

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B-14 

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C-1 

Appendix C 

Primer for TANKS Model Users 
Version 2.1.1 

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C-2 

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Final ICR Version – Corrected Appendix C—Primer for TANKS Model Users 

C-3 

C. Primer for TANKS Model Users 

In general, EPA recommends that the emission estimation procedures detailed in Chapter 7.1 of AP-42 

(U.S. EPA, 1995a) be used to calculate air pollutant emissions from organic liquid storage vessels. There 

are many tools available, such as TANKS v4.09D emission estimation software that can be used to 

perform the necessary calculations detailed in Chapter 7.1 of AP-42 (U.S. EPA, 1995a). TANKS v4.09D 

software can be downloaded for free at http://www.epa.gov/ttn/chief/software/tanks/index.html (under the 

How to Get TANKS 4.09D link). Because TANKS v4.09D is widely used, this appendix is included to 

provide tips and insights on using the TANKS program. This appendix will also highlight some potential 

enhancements to the modeling of storage tank emissions that may be implemented when using the AP-42 

equations directly (or potentially other software packages) that are not currently afforded by TANKS 

v4.09D. 

The calculations in the TANKS program are specific to the type of tank, and the results will be highly 

dependent on the type of liquid stored. Each individual storage tank should be modeled separately. There 

may be instances in which a set of tanks have identical properties and materials and very similar 

throughputs so that the emissions from a single storage tank can be modeled and used as the emissions for 

each tank in the set. However, this type of “model tank” analysis should be used and generally be limited 

to situations in which limited data are available (i.e., if throughput is only measured by product and not by 

individual tank, then modeling a group of identical tanks used to store that product may be necessary). 

For inventories developed by the petroleum refinery or storage tank operators, it is recommended that 

individual tank data be entered into the TANKS program (or other similar software), and the emission 

results for individual tanks be reported in the emission inventory. For some uses of the emission inventory 

data, specific emission location and source characteristics data are needed. These data become lost or less 

accurate when emissions from a group of tanks (e.g., those that would be assigned to the same source 

classification code [SCC]) are aggregated when reporting to the emission inventory. 

To enter a new tank, first select the tank type from the drop-down menu labeled “Create a New Tank 

Record.” There are five basic tank types: horizontal fixed roof tanks; vertical fixed roof tanks; external 

floating roof tanks; internal floating roof tanks; and domed external floating roof tanks. Next, fill out the 

information in the Identification, Physical Characteristics, Site Selection, Tank Contents, and Monthly 

Calculations tabs with the appropriate information. Tables C-1 and C-2 show the required input by tank 

orientation. These inputs may either be from a drop-down list based on the TANKS database for location, 

tank color, and other tank-specific information or taken directly from process data. In TANKS, selecting 

the city will set the meteorological data that will be used in the calculations. After entering all of the 

requested data, the tank information can be saved by pressing the Save button at the bottom of the gray 

window. 
Version 2.1.1 

Final ICR Version – Corrected Appendix C—Primer for TANKS Model Users 

C-4 

Table C-1. TANKS Inputs by Tank Configuration-Tank Dimensions and Characteristics 

Horizontal 

Tank 

Vertical 

Fixed-Roof 

Tank 

Internal 

Floating 

Roof 

External 

Floating 

Roof 

Domed 

External 

Floating 

Roof 

Identification number z z z z z

Description z z z z z

State z z z z z

City z z z z z

Company z z z z z

Dimensions and Characteristics 

Shell height (feet [ft]) z z 

Diameter (shell diameter, ft) z z z

Volume z z

Maximum liquid height z z 

Average liquid height z z 

Working volume (gallons) z z 

Turnovers per year z z z z

Net throughput (gallons per year 

[gal/yr]) z z z

Is tank heated? z z 

Is tank underground? z 

Self-supporting roof z 

Number of columns z

Effective column diameter z

Roof type z z

Roof fitting category z z

Tank construction z z
Version 2.1.1 

Final ICR Version – Corrected Appendix C—Primer for TANKS Model Users 

C-5 

Table C-2. TANKS Inputs by Tank Configuration-Specific Attributes, Site Selection, and Contents 

Horizontal 

Tank 

Vertical 

Fixed-Roof 

Tank 

Internal 

Floating 

Roof 

External 

Floating 

Roof 

Domed 

External 

Floating 

Roof 

Tank/Shell/Roof Characteristics 

(External) shell/paint color/shade z z z z z

(External) shell/paint shell condition z z z z z

Internal shell condition z 

Rim Seal 

Primary seal z z z

Secondary seal z z z

Deck Characteristics 

Deck type z 

Deck fitting category z 

Breather Vent Settings 

Vacuum setting (psig) z z 

Pressure setting (psig) z z 

Roof Characteristics 

Color/shade z z 

Condition z 

Type z

Height (ft) z

Roof paint condition z 

Site Selection 

Nearest major city z z z z z

Daily average ambient temperature z z z z z

Annual average maximum temperature z z z z z

Annual average minimum temperature z z z z z

Average wind speed z z z z z

Annual average solar insulation factor 

(Btu/(ft × ft ×day) z z z z z

Atmospheric pressure (pounds of force 

per square inch absolute [psia]) z z z z z

Tank Contents 

Chemical category of liquid z z z z z

Single or multi-component liquid z z z z z

Mixture properties, if applicable z z z z z

Throughput by month z z z z z
Version 2.1.1 

Final ICR Version – Corrected Appendix C—Primer for TANKS Model Users 

C-6 

For the internal floating roof tank, the external floating roof tank, and the domed external floating roof 

tank, it is possible to define the fitting type to represent specific characteristics of the tanks at your 

facility. Using facility-specific tank information will ensure that the calculated emission estimates are as 

accurate as possible. The fittings information can be entered under the Physical Characteristics tab by 

selecting the View/Add Fittings button and providing the fitting type and status. Table C-3 contains a list 

of the different fitting types and status options. Using the information provided in Tables C-1 through 

C-3, the tanks program estimates the anticipated emissions specifically for the particular location, tank 

type, and process characteristics. 

Once a tank is entered, you can use or import that tank as a starting point for adding new tanks. To copy 

data from an existing tank to a new tank, select DATA, then TANKS, and then New Record from the 

TANKS 4.0 main menu or by selecting the appropriate acronym from the toolbar on the main screen. 

Click on the Copy button at the bottom of the tank pop-up screen. Then click on the tank that you want to 

copy from a dropdown menu, and then select whether you want to copy just the Tank Data, just the 

Liquid Data, or both (“All Data”). Simply opening an existing tank and changing the name does not 

create a new tank record, it only renames and replaces the old record. 

Because TANKS uses preloaded meteorological data, year-to-year variations in emissions will only result 

from differing throughput or tank service (storing different material than in previous years). If 

accommodated in other software packages, meteorological data that are specific to the reporting year 

should be used because this information will provide more accurate emission values. Studies have 

indicated that emissions may vary by up to 25% from year to year depending on the meteorological 

conditions for that year (Coburn and Icenhour, 2008). Also, if accommodated in other software packages, 

directly measured liquid temperatures or monthly average ambient temperatures should be used for the 

bulk liquid temperatures, and these values should be used to calculate monthly average emission rates. In 

TANKS, even when using the monthly calculations option, unfortunately the annual average liquid 

temperature is still used. As such, unless there are extreme differences in throughputs by month, the 

monthly calculation procedures used in TANKS are unlikely to significantly alter the annual emission 

estimates. Based on limited model analyses, monthly variations in liquid temperature may be significant 

and may influence the annual average emissions if monthly emissions are estimated more rigorously (i.e., 

by accounting for variations in bulk liquid temperature) (Coburn and Icenhour, 2008). 

The TANKS program typically provides total hydrocarbon emission estimates. TANKS is also designed 

to calculate the individual component emissions from known mixtures and to estimate emissions from 

typical refined petroleum products. More than 100 organic liquids are included in the TANKS chemical 

database, but it is also designed to analyze other substances based on their chemical properties and the 

parameters shown in Table C-4. If you store a component or mixture in the storage tanks and have 

available property data (i.e. chemical database inputs), then these can be added to the TANKS program. 

In addition to the analysis of individual chemicals, the TANKS program also has the capability to 

calculate the characteristics of defined mixtures. When the “Multiple” option is selected for the “Singleor Multi-Component Liquid” option, and “Full Speciation” is selected for the “Speciation” option, then 

the full chemical profile can be created using the “View/Add Components” button. Any defined chemical, 

including those defined using the criteria in Table C-4, can be included in the mixture as a component as 

long as the percentage of total liquid weight or relative weight is known. With the chemical components 

and their relative percentages and/or weights entered, the menu can be closed, and the mixture properties 

can be calculated by clicking on the Calculate Mixture Properties button. 
Version 2.1.1 

Final ICR Version – Corrected Appendix C—Primer for TANKS Model Users 

C-7 

Table C-3. Fitting Type and Status Option Inputs for TANKS Program 

Fitting Type Status 

Access hatch (24 inches in diameter) 

Bolted cover, gasketed 

Unbolted cover, gasketed 

Unbolted cover, ungasketed 

Automatic gauge float well 

Bolted cover, gasketed 

Unbolted cover, gasketed 

Unbolted cover, ungasketed 

Column well (24 inches in diameter) 

Built-up column, sliding cover, gasketed 

Built-up column, sliding cover, ungasketed 

Pipe column, flexible fabric sleeve seal 

Pipe column, sliding cover, gasketed 

Pipe column, sliding cover, ungasketed 

Gauge-hatch/sample well (8 inches in diameter) Weighted mechanical actuation, gasketed 

Weighted mechanical actuation, ungasketed 

Ladder well (36 inches in diameter) Sliding cover, gasketed 

Sliding cover, ungasketed 

Rim vent (6 inches In diameter) Weighted mechanical actuation, gasketed 

Weighted mechanical actuation, ungasketed 

Roof drain (3 inches in diameter) Open 

90% closed 

Roof leg (3 inches In diameter) 

Adjustable, pontoon area, ungasketed 

Adjustable, center area, ungasketed 

Adjustable, double-deck roofs 

Fixed 

Adjustable, pontoon area, gasketed 

Adjustable, pontoon area, sock 

Adjustable, center area, gasketed 

Adjustable, center area, sock 

Roof leg or hanger well Adjustable 

Fixed 

Sample pipe or well (24 inches In diameter) 

Slotted pipe, sliding cover, gasketed 

Slotted pipe, sliding cover, ungasketed 

Slit fabric seal 10% open 

Slotted guide-pole/sample well 

Sliding cover, without float, ungasketed 

Sliding cover, with float, ungasketed 

Sliding cover, without float, gasketed 

Sliding cover, with float, gasketed 

Sliding cover, with pole wiper, gasketed 

Sliding cover, with pole sleeve, gasketed 

Sliding cover, with float, wiper, gasketed 

Sliding cover, with float, sleeve, wiper, gasketed 

Sliding cover, with pole sleeve, wiper, gasketed 

Stub drain (1 inch in diameter) None listed 

Unslotted guide-pole well 

Sliding cover, ungasketed 

Sliding cover, gasketed 

Sliding cover, with sleeve ungasketed 

Sliding cover, with sleeve, gasketed 

Sliding cover, with wiper, gasketed 

Vacuum breaker (10 inches in diameter) Weighted mechanical actuation, gasketed 

Weighted mechanical actuation, ungasketed 
Version 2.1.1 

Final ICR Version – Corrected Appendix C—Primer for TANKS Model Users 

C-8 

Table C-4. Chemical Database Inputs for TANKS 

Chemical name 

CAS number (Chemical Abstracts Service number) 

Category 

Liquid molecular weight 

Liquid density (lb/gal; ~60°F) 

Vapor molecular weight 

Vapor pressure at 40°F, 50°F, 60°F, 70°F, 80°F, 90°F, 100°F 

Constants for Antoine's equation using °C (A, B, and C) 

Constants for Antoine's equation using °K (A and B) 

Reid vapor pressure (psia): Distillates and crude oil 

ASTM slope: distillates only 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-1 

Appendix D 

Emission Factors from Air Toxic Emission Factors for 

Combustion Sources Using Petroleum Based Fuels – 

Final Report, Volume 2 – Development of Emission 

Factors Using CARB Approach
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-2 

[This page intentionally left blank.] 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-3 

D. Emission Factors from Air Toxic Emission Factors for Combustion 

Sources Using Petroleum Based Fuels – Final Report, Volume 2 – 

Development of Emission Factors Using CARB Approach

 Detect Ratio: Ratio of detected values to the sum of detected and nondetected values. 

 RSD: 100 times the standard deviation divided by the arithmetic average. 

 Uncertainty: 100 times the 95% confidence interval divided by the arithmetic average. 

Dioxin Acronyms 

4D 2378 2,3,7,8-Tetrachlorodibenzo-p-dioxin. 

4D Other Tetrachlorodibenzo-p-dioxin other. 

4D Total Tetrachlorodibenzo-p-dioxin total. 

5D 12378 1,2,3,7,8-Pentachlorodibenzo-p-dioxin. 

5D Other Pentachlorodibenzo-p-dioxin other. 

5D Total Pentachlorodibenzo-p-dioxin total. 

6D 123478 1,2,3,4,7,8-Hexachlorodibenzo-p-dioxin. 

6D 123678 1,2,3,6,7,8-Hexachlorodibenzo-p-dioxin. 

6D 123789 1,2,3,7,8,9-Hexachlorodibenzo-p-dioxin. 

6D Other Hexachlorodibenzo-p-dioxin other. 

6D Total Hexachlorodibenzo-p-dioxin. 

7D 1234678 1,2,3,4,7,8-Heptachlorodibenzo-p-dioxin. 

7D Other Heptachlorodibenzo-p-dioxin other. 

7D Total Heptachlorodibenzo-p-dioxin total. 

8D Octachlorodibenzo-p-dioxin. 

Furan Acronyms 

4F 2378 2,3,7,8-Tetrachlorodibenzofuran. 

4F Other Tetrachlorodibenzofuran other. 

4F Total Tetrachlorodibenzofuran total. 

5F 12378 1,2,3,7,8-Pentachlorodibenzofuran. 

5F 23478 2,3,4,7,8-Pentachlorodibenzofuran. 

5F Other Pentachlorodibenzofuran other. 

5F Total Pentachlorodibenzofuran total. 

6F 123478 1,2,3,4,7,8-Hexachlorodibenzofuran. 

6F 123678 1,2,3,6,7,8-Hexachlorodibenzofuran. 

6F 123789 1,2,3,7,8,9-Hexachlorodibenzofuran. 

6F 234678 2,3,4,6,7,8-Hexachlorodibenzofuran. 

6F Other Hexachlorodibenzofuran other. 

6F Total Hexachlorodibenzofuran total. 

7F 1234678 1,2,3,4,6,7,8-Heptachlorodibenzofuran. 

7F 1234789 1,2,3,4,7,8,9-Heptachlorodibenzofuran. 

7F Other Heptachlorodibenzofuran other. 

7F Total Heptachlorodibenzofuran total. 

8F Octachlorodibenzofuran. 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-4 

Table D-1a. Summary of Data for Emission Factor Development – 

Asphalt Blowing with Blow Cycle and a Thermal Oxidizer 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acetaldehyde C3-v- 1.78E-03 1.78E-03 1.78E-03 1.78E-03 1 0.00 0.00 1.00 

Arsenic D3-v- 1.31E-02 1.31E-02 1.31E-02 1.31E-02 1 0.00 0.00 0.00 

Benzene E3-v- 3.16E-01 3.16E-01 3.16E-01 3.16E-01 1 0.00 0.00 0.00 

Beryllium D3-v- 2.63E-03 2.63E-03 2.63E-03 2.63E-03 1 0.00 0.00 0.00 

Cadmium D3-v- 5.25E-03 5.25E-03 5.25E-03 5.25E-03 1 0.00 0.00 0.00 

Chromium (Hex) C3-v- 3.17E-03 3.17E-03 3.17E-03 3.17E-03 1 0.00 0.00 1.00 

Chromium (Total) C3-v- 4.18E-02 4.18E-02 4.18E-02 4.18E-02 1 0.00 0.00 1.00 

Copper D3-v- 4.75E-02 4.75E-02 4.75E-02 4.75E-02 1 0.00 0.00 1.00 

Ethylbenzene E3-v- 8.61E-01 8.61E-01 8.61E-01 8.61E-01 1 0.00 0.00 0.00 

Formaldehyde C3-v- 3.55E-03 3.55E-03 3.55E-03 3.55E-03 1 0.00 0.00 1.00 

HCl C3-v- 2.21E-03 2.21E-03 2.21E-03 2.21E-03 1 0.00 0.00 1.00 

Hydrogen Sulfide A3-v- 2.07E+00 2.07E+00 2.07E+00 2.07E+00 1 0.00 0.00 0.00 

Lead D3-v- 5.25E-02 5.25E-02 5.25E-02 5.25E-02 1 0.00 0.00 0.00 

Manganese D3-v- 1.23E-01 1.23E-01 1.23E-01 1.23E-01 1 0.00 0.00 1.00 

Mercury A3-v- 9.07E-03 9.07E-03 9.07E-03 9.07E-03 1 0.00 0.00 1.00 

Nickel D3-v- 6.65E-02 6.65E-02 6.65E-02 6.65E-02 1 0.00 0.00 0.00 

Phenol C3-v- 7.57E-02 7.57E-02 7.57E-02 7.57E-02 1 0.00 0.00 1.00 

Selenium D3-v- 1.31E-02 1.31E-02 1.31E-02 1.31E-02 1 0.00 0.00 0.00 

Xylene (Total) E3-v- 8.61E-01 8.61E-01 8.61E-01 8.61E-01 1 0.00 0.00 0.00 

Zinc D3-v- 8.41E-01 8.41E-01 8.41E-01 8.41E-01 1 0.00 0.00 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-5 

Table D-1b. Summary of Data for Emission Factor Development – 

Asphalt Blowing with Blow Cycle and a Thermal Oxidizer 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acetaldehyde C3-v- 1.67E-06 1.67E-06 1.67E-06 1.67E-06 1 0.00 0.00 1.00 

Arsenic D3-v- 1.23E-05 1.23E-05 1.23E-05 1.23E-05 1 0.00 0.00 0.00 

Benzene E3-v- 2.98E-04 2.98E-04 2.98E-04 2.98E-04 1 0.00 0.00 0.00 

Beryllium D3-v- 2.47E-06 2.47E-06 2.47E-06 2.47E-06 1 0.00 0.00 0.00 

Cadmium D3-v- 4.94E-06 4.94E-06 4.94E-06 4.94E-06 1 0.00 0.00 0.00 

Chromium (Hex) C3-v- 2.99E-06 2.99E-06 2.99E-06 2.99E-06 1 0.00 0.00 1.00 

Chromium (Total) C3-v- 3.94E-05 3.94E-05 3.94E-05 3.94E-05 1 0.00 0.00 1.00 

Copper D3-v- 4.47E-05 4.47E-05 4.47E-05 4.47E-05 1 0.00 0.00 1.00 

Ethylbenzene E3-v- 8.10E-04 8.10E-04 8.10E-04 8.10E-04 1 0.00 0.00 0.00 

Formaldehyde C3-v- 3.34E-06 3.34E-06 3.34E-06 3.34E-06 1 0.00 0.00 1.00 

HCl C3-v- 2.08E-06 2.08E-06 2.08E-06 2.08E-06 1 0.00 0.00 1.00 

Hydrogen Sulfide A3-v- 1.95E-03 1.95E-03 1.95E-03 1.95E-03 1 0.00 0.00 0.00 

Lead D3-v- 4.94E-05 4.94E-05 4.94E-05 4.94E-05 1 0.00 0.00 0.00 

Manganese D3-v- 1.16E-04 1.16E-04 1.16E-04 1.16E-04 1 0.00 0.00 1.00 

Mercury A3-v- 8.53E-06 8.53E-06 8.53E-06 8.53E-06 1 0.00 0.00 1.00 

Nickel D3-v- 6.26E-05 6.26E-05 6.26E-05 6.26E-05 1 0.00 0.00 0.00 

Phenol C3-v- 7.12E-05 7.12E-05 7.12E-05 7.12E-05 1 0.00 0.00 1.00 

Selenium D3-v- 1.23E-05 1.23E-05 1.23E-05 1.23E-05 1 0.00 0.00 0.00 

Xylene (Total) E3-v- 8.10E-04 8.10E-04 8.10E-04 8.10E-04 1 0.00 0.00 0.00 

Zinc D3-v- 7.91E-04 7.91E-04 7.91E-04 7.91E-04 1 0.00 0.00 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-6 

Table D-2a. Summary of Data for Emission Factor Development – 

Asphalt Blowing with No Blow Cycle and a Thermal Oxidizer 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acetaldehyde C3-v- 4.32E-03 4.32E-03 4.32E-03 4.32E-03 1 0.00 0.00 1.00 

Arsenic D3-v- 1.16E-02 1.16E-02 1.16E-02 1.16E-02 1 0.00 0.00 0.00 

Benzene E3-v- 2.80E-01 2.80E-01 2.80E-01 2.80E-01 1 0.00 0.00 0.00 

Beryllium D3-v- 2.33E-03 2.33E-03 2.33E-03 2.33E-03 1 0.00 0.00 0.00 

Cadmium D3-v- 4.65E-03 4.65E-03 4.65E-03 4.65E-03 1 0.00 0.00 0.00 

Chromium (Hex) C3-v- 3.28E-03 3.28E-03 3.28E-03 3.28E-03 1 0.00 0.00 0.00 

Chromium (Total) C3-v- 1.42E-02 1.42E-02 1.42E-02 1.42E-02 1 0.00 0.00 0.00 

Copper D3-v- 3.79E-02 3.79E-02 3.79E-02 3.79E-02 1 0.00 0.00 1.00 

Ethylbenzene E3-v- 7.62E-01 7.62E-01 7.62E-01 7.62E-01 1 0.00 0.00 0.00 

Formaldehyde C3-v- 1.30E-02 1.30E-02 1.30E-02 1.30E-02 1 0.00 0.00 1.00 

HCl C3-v- 8.22E-04 8.22E-04 8.22E-04 8.22E-04 1 0.00 0.00 1.00 

Hydrogen Sulfide A3-v- 1.83E+00 1.83E+00 1.83E+00 1.83E+00 1 0.00 0.00 0.00 

Lead D3-v- 4.65E-02 4.65E-02 4.65E-02 4.65E-02 1 0.00 0.00 0.00 

Manganese D3-v- 2.07E-01 2.07E-01 2.07E-01 2.07E-01 1 0.00 0.00 1.00 

Mercury A3-v- 8.53E-03 8.53E-03 8.53E-03 8.53E-03 1 0.00 0.00 1.00 

Nickel D3-v- 6.01E-02 6.01E-02 6.01E-02 6.01E-02 1 0.00 0.00 0.00 

Phenol C3-v- 4.64E-02 4.64E-02 4.64E-02 4.64E-02 1 0.00 0.00 1.00 

Selenium D3-v- 1.16E-02 1.16E-02 1.16E-02 1.16E-02 1 0.00 0.00 0.00 

Xylene (Total) E3-v- 7.62E-01 7.62E-01 7.62E-01 7.62E-01 1 0.00 0.00 0.00 

Zinc D3-v- 5.35E-01 5.35E-01 5.35E-01 5.35E-01 1 0.00 0.00 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-7 

Table D-2b. Summary of Data for Emission Factor Development – 

Asphalt Blowing with No Blow Cycle and a Thermal Oxidizer 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acetaldehyde C3-v- 4.07E-06 4.07E-06 4.07E-06 4.07E-06 1 0.00 0.00 1.00 

Arsenic D3-v- 1.09E-05 1.09E-05 1.09E-05 1.09E-05 1 0.00 0.00 0.00 

Benzene E3-v- 2.64E-04 2.64E-04 2.64E-04 2.64E-04 1 0.00 0.00 0.00 

Beryllium D3-v- 2.19E-06 2.19E-06 2.19E-06 2.19E-06 1 0.00 0.00 0.00 

Cadmium D3-v- 4.37E-06 4.37E-06 4.37E-06 4.37E-06 1 0.00 0.00 0.00 

Chromium (Hex) C3-v- 3.09E-06 3.09E-06 3.09E-06 3.09E-06 1 0.00 0.00 0.00 

Chromium (Total) C3-v- 1.34E-05 1.34E-05 1.34E-05 1.34E-05 1 0.00 0.00 0.00 

Copper D3-v- 3.56E-05 3.56E-05 3.56E-05 3.56E-05 1 0.00 0.00 1.00 

Ethylbenzene E3-v- 7.17E-04 7.17E-04 7.17E-04 7.17E-04 1 0.00 0.00 0.00 

Formaldehyde C3-v- 1.22E-05 1.22E-05 1.22E-05 1.22E-05 1 0.00 0.00 1.00 

HCl C3-v- 7.74E-07 7.74E-07 7.74E-07 7.74E-07 1 0.00 0.00 1.00 

Hydrogen Sulfide A3-v- 1.73E-03 1.73E-03 1.73E-03 1.73E-03 1 0.00 0.00 0.00 

Lead D3-v- 4.38E-05 4.38E-05 4.38E-05 4.38E-05 1 0.00 0.00 0.00 

Manganese D3-v- 1.95E-04 1.95E-04 1.95E-04 1.95E-04 1 0.00 0.00 1.00 

Mercury A3-v- 8.03E-06 8.03E-06 8.03E-06 8.03E-06 1 0.00 0.00 1.00 

Nickel D3-v- 5.65E-05 5.65E-05 5.65E-05 5.65E-05 1 0.00 0.00 0.00 

Phenol C3-v- 4.37E-05 4.37E-05 4.37E-05 4.37E-05 1 0.00 0.00 1.00 

Selenium D3-v- 1.09E-05 1.09E-05 1.09E-05 1.09E-05 1 0.00 0.00 0.00 

Xylene (Total) E3-v- 7.17E-04 7.17E-04 7.17E-04 7.17E-04 1 0.00 0.00 0.00 

Zinc D3-v- 5.04E-04 5.04E-04 5.04E-04 5.04E-04 1 0.00 0.00 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-8 

Table D-3a. Summary of Data for Emission Factor Development – Boilers Firing Fuel Oil 

Substance 

CARB 

Rating 

Emission Factor (lb/Mgal) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene B3-v0 8.93E-07 8.50E-07 1.56E-06 3.34E-07 2 67.31 53.86 0.87 

Acenaphthylene B3-v0 3.17E-07 3.28E-07 3.58E-07 2.34E-07 2 14.29 11.43 0.00 

Acetaldehyde A3-v1 1.04E-03 4.98E-04 3.35E-03 2.80E-04 2 116.00 92.82 0.75 

Acrolein A3-v0 2.17E-03 1.75E-03 3.35E-03 1.43E-03 1 47.31 53.53 0.00 

Anthracene B3-v1 3.22E-07 2.84E-07 7.42E-07 1.90E-08 2 98.99 79.20 0.94 

Arsenic B3-v0 1.44E-03 1.44E-03 1.68E-03 1.19E-03 1 17.00 19.24 0.00 

Benzene A3-v0 4.63E-03 4.67E-03 4.76E-03 4.47E-03 1 3.26 3.69 0.00 

Benzo(a)anthracene B3-v1 2.04E-07 2.21E-07 3.58E-07 2.98E-08 2 78.58 62.87 0.00 

Benzo(a)pyrene B3-v0 2.09E-07 2.24E-07 3.58E-07 4.61E-08 2 73.55 58.55 0.00 

Benzo(b)fluoranthene B3-v0 1.21E-06 1.02E-06 2.36E-06 3.34E-07 2 73.99 59.20 0.40 

Benzo(e)pyrene C3-v0 8.53E-07 1.03E-06 1.12E-06 4.11E-07 1 45.15 51.09 0.00 

Benzo(g,h,i)perylene B3-v0 9.99E-07 8.47E-07 2.20E-06 3.34E-07 2 77.58 62.08 0.00 

Benzo(k)fluoranthene B3-v1 2.08E-07 2.37E-07 3.58E-07 2.98E-08 2 76.76 61.42 0.00 

Beryllium B3-v0 6.29E-05 6.35E-05 7.03E-05 5.50E-05 1 12.22 13.83 0.00 

1,3-Butadiene B3-v1 6.17E-03 5.97E-03 1.18E-02 8.95E-04 2 93.74 75.01 0.00 

Cadmium B3-v0 8.56E-04 6.58E-04 1.26E-03 6.47E-04 1 41.15 46.57 0.00 

Chloroform A3-v0 4.69E-03 5.00E-03 5.10E-03 4.78E-03 1 3.26 3.69 0.00 

2-Chloronaphthalene C3-v0 2.27E-08 2.33E-08 2.86E-08 1.63E-08 1 27.13 30.70 0.00 

Chromium (Hex) A3-v0 1.15E-03 1.15E-03 1.21E-03 1.09E-03 1 4.95 5.60 0.00 

Chromium (Total) A3-v0 4.83E-03 5.18E-03 5.85E-03 3.45E-03 1 25.70 29.08 1.00 

Chrysene B3-v0 3.88E-06 3.26E-06 8.57E-06 1.16E-06 2 78.87 63.11 1.00 

Copper B3-v0 3.86E-03 2.02E-03 8.67E-03 8.92E-04 1 108.86 123.19 1.00 

Dibenz(a,h)anthracene B3-v1 7.06E-07 3.43E-07 2.68E-06 2.07E-07 2 136.88 109.33 0.00 

Dioxin: 4D 2378 C3-v0 6.33E-10 5.71E-10 7.83E-10 5.46E-10 1 20.50 23.20 0.00 

Dioxin: 5D 12378 C3-v0 3.68E-10 2.73E-10 5.71E-10 2.61E-10 1 47.67 53.94 0.00 

Dioxin: 6D 123478 C3-v0 3.68E-10 2.73E-10 5.71E-10 2.61E-10 1 47.67 53.94 0.00 

Dioxin: 6D 123678 C3-v0 3.68E-10 2.73E-10 5.71E-10 2.61E-10 1 47.67 53.94 0.25 

Dioxin: 6D 123789 C3-v0 3.68E-10 2.73E-10 5.71E-10 2.61E-10 1 47.67 53.94 0.25 

Dioxin: 7D 1234678 C3-v0 3.12E-09 2.86E-09 5.19E-09 1.30E-09 1 62.77 71.03 1.00 

Dioxin: 8D C3-v0 7.50E-08 8.28E-08 1.23E-07 1.93E-08 1 69.66 78.83 1.00 

Fluoranthene B3-v1 7.78E-06 6.18E-06 1.65E-05 9.31E-07 2 87.83 70.27 1.00 

Fluorene B3-v0 4.65E-06 4.60E-06 8.48E-06 8.93E-07 2 83.31 66.66 1.00 

Formaldehyde A3-v1 6.72E-03 7.14E-03 1.67E-02 2.83E-04 2 91.09 72.89 0.18 

Furan: 4F 2378 C3-v0 8.16E-10 7.83E-10 1.09E-09 5.71E-10 1 32.18 36.42 1.00 

Furan: 5F 12378 C3-v0 4.59E-10 5.46E-10 5.71E-10 2.61E-10 1 37.52 42.46 0.00 

Furan: 5F 23478 C3-v0 4.59E-10 5.46E-10 5.71E-10 2.61E-10 1 37.52 42.46 0.00 

Furan: 6F 123478 C3-v0 3.64E-10 2.86E-10 5.46E-10 2.61E-10 1 43.44 49.15 0.50 

Furan: 6F 123678 C3-v0 2.73E-10 2.73E-10 2.86E-10 2.61E-10 1 4.51 5.10 0.33 

(continued) 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-9 

Table D-3a. Summary of Data for Emission Factor Development – Boilers Firing Fuel Oil 

(continued) 

Substance 

CARB 

Rating 

Emission Factor (lb/Mgal) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Furan: 6F 123789 C3-v0 3.68E-10 2.73E-10 5.71E-10 2.61E-10 1 47.67 53.94 0.00 

Furan: 6F 234678 C3-v0 5.51E-10 5.71E-10 8.20E-10 2.61E-10 1 50.85 57.54 0.50 

Furan: 7F 1234678 C3-v0 1.44E-09 1.14E-09 2.09E-09 1.09E-09 1 38.89 44.01 1.00 

Furan: 7F 1234789 C3-v0 4.64E-10 2.73E-10 8.57E-10 2.61E-10 1 73.43 83.10 0.00 

Furan: 8F C3-v0 7.15E-09 7.14E-09 1.04E-08 3.91E-09 1 45.27 51.23 1.00 

Indeno(1,2,3-cd) pyrene B3-v0 4.59E-07 3.55E-07 7.82E-07 2.90E-07 2 43.75 35.01 0.00 

Lead B3-v0 1.56E-03 8.59E-04 3.32E-03 4.89E-04 1 98.91 111.92 0.00 

Manganese B3-v0 5.81E-03 2.82E-03 1.22E-02 2.40E-03 1 95.34 107.89 1.00 

Mercury B3-v0 1.03E-05 9.04E-06 1.47E-05 7.19E-06 1 38.06 43.07 0.00 

2-Methylnaphthalene C3-v0 1.09E-05 1.07E-05 1.22E-05 9.76E-06 1 11.52 13.04 1.00 

Naphthalene B3-v0 6.07E-05 6.22E-05 8.12E-05 4.25E-05 2 25.60 20.48 1.00 

Nickel B3-v0 3.34E-01 3.05E-01 4.06E-01 2.90E-01 1 18.95 21.44 1.00 

Perylene C3-v0 1.09E-07 5.95E-08 2.20E-07 4.88E-08 1 87.56 99.09 0.00 

Phenanthrene B3-v0 1.10E-05 1.10E-05 1.99E-05 3.29E-06 2 57.86 46.30 1.00 

Propylene A3-v0 2.19E-02 2.21E-02 2.25E-02 2.11E-02 1 3.26 3.69 0.00 

Pyrene B3-v1 4.01E-06 2.35E-06 1.08E-05 3.53E-07 2 110.05 88.06 0.97 

Selenium B3-v0 2.88E-03 3.59E-03 3.61E-03 1.45E-03 1 43.13 48.81 0.17 

Toluene A3-v0 5.75E-03 5.79E-03 5.91E-03 5.55E-03 1 3.26 3.69 0.00 

Xylene (Total) A3-v0 1.10E-02 1.11E-02 1.14E-02 1.06E-02 1 3.26 3.69 0.00 

Zinc B3-v0 1.60E-02 8.61E-03 3.09E-02 8.56E-03 1 80.41 90.99 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-10 

Table D-3b. Summary of Data for Emission Factor Development – Boilers Firing Fuel Oil 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene B3-v0 6.00E-09 5.71E-09 1.06E-08 2.14E-09 2 69.26 55.42 0.87 

Acenaphthylene B3-v0 2.09E-09 2.16E-09 2.29E-09 1.59E-09 2 12.32 9.86 0.00 

Acetaldehyde A3-v1 6.99E-06 3.33E-06 2.28E-05 1.79E-06 2 117.49 94.01 0.75 

Acrolein A3-v0 1.48E-05 1.19E-05 2.28E-05 9.69E-06 1 47.31 53.53 0.00 

Anthracene B3-v1 2.07E-09 1.83E-09 4.76E-09 1.29E-10 2 98.24 78.60 0.94 

Arsenic B3-v0 9.76E-06 9.76E-06 1.14E-05 8.10E-06 1 17.00 19.24 0.00 

Benzene A3-v0 3.15E-05 3.17E-05 3.24E-05 3.04E-05 1 3.26 3.69 0.00 

Benzo(a)anthracene B3-v1 1.32E-09 1.44E-09 2.29E-09 2.03E-10 2 77.09 61.68 0.00 

Benzo(a)pyrene B3-v0 1.36E-09 1.46E-09 2.29E-09 3.13E-10 2 71.84 57.48 0.00 

Benzo(b)fluoranthene B3-v0 8.11E-09 6.77E-09 1.60E-08 2.14E-09 2 75.81 60.66 0.40 

Benzo(e)pyrene C3-v0 5.80E-09 7.00E-09 7.60E-09 2.80E-09 1 45.15 51.09 0.00 

Benzo(g,h,i)perylene B3-v0 6.72E-09 5.69E-09 1.50E-08 2.14E-09 2 79.36 63.50 0.00 

Benzo(k)fluoranthene B3-v1 1.34E-09 1.55E-09 2.29E-09 2.03E-10 2 75.32 60.26 0.00 

Beryllium B3-v0 4.28E-07 4.32E-07 4.78E-07 3.74E-07 1 12.22 13.83 0.00 

1,3-Butadiene B3-v1 4.18E-05 4.04E-05 8.00E-05 5.74E-06 2 94.58 75.68 0.00 

Cadmium B3-v0 5.82E-06 4.47E-06 8.58E-06 4.40E-06 1 41.15 46.57 0.00 

Chloroform A3-v0 3.37E-05 3.40E-05 3.47E-05 3.25E-05 1 3.26 3.69 0.00 

2-Chloronaphthalene C3-v0 1.54E-10 1.58E-10 1.94E-10 1.11E-10 1 27.13 30.70 0.00 

Chromium (Hex) A3-v0 7.82E-06 7.85E-06 8.20E-06 7.43E-06 1 4.95 5.60 0.00 

Chromium (Total) A3-v0 3.28E-05 3.52E-05 3.98E-05 2.34E-05 1 25.70 29.08 1.00 

Chrysene B3-v0 2.62E-08 2.19E-08 5.83E-08 7.46E-09 2 80.59 64.48 1.00 

Copper B3-v0 2.62E-05 1.37E-05 5.89E-05 6.07E-06 1 108.86 123.19 1.00 

Dibenz(a,h)anthracene B3-v1 4.73E-09 2.20E-09 1.82E-08 1.41E-09 2 139.45 111.58 0.00 

Dioxin:4D 2378 C3-v0 4.31E-12 3.88E-12 5.32E-12 3.71E-12 1 20.50 23.20 0.00 

Dioxin:5D 12378 C3-v0 2.50E-12 1.86E-12 3.88E-12 1.77E-12 1 47.67 53.94 0.00 

Dioxin:6D 123478 C3-v0 2.50E-12 1.86E-12 3.88E-12 1.77E-12 1 47.67 53.94 0.00 

Dioxin:6D 123678 C3-v0 2.50E-12 1.86E-12 3.88E-12 1.77E-12 1 47.67 53.94 0.25 

Dioxin:6D 123789 C3-v0 2.50E-12 1.86E-12 3.88E-12 1.77E-12 1 47.67 53.94 0.25 

Dioxin:7D 1234678 C3-v0 2.12E-11 1.94E-11 3.53E-11 8.87E-12 1 62.77 71.03 1.00 

Dioxin:8D C3-v0 5.10E-10 5.63E-10 8.36E-10 1.31E-10 1 69.66 78.83 1.00 

Fluoranthene B3-v1 5.25E-08 4.14E-08 1.12E-07 5.97E-09 2 89.14 71.33 1.00 

Fluorene B3-v1 3.14E-08 3.10E-08 5.76E-08 5.73E-09 2 84.62 67.71 1.00 

Formaldehyde A3-v1 4.52E-05 4.72E-05 1.14E-04 1.82E-06 2 92.14 73.72 0.18 

Furan:4F 2378 C3-v0 5.54E-12 5.32E-12 7.43E-12 3.88E-12 1 32.18 36.42 1.00 

Furan:5F 12378 C3-v0 3.12E-12 3.71E-12 3.88E-12 1.77E-12 1 37.52 42.46 0.00 

Furan:5F 23478 C3-v0 3.12E-12 3.71E-12 3.88E-12 1.77E-12 1 37.52 42.46 0.00 

Furan:6F 123478 C3-v0 2.48E-12 1.94E-12 3.71E-12 1.77E-12 1 43.44 49.15 0.50 

Furan:6F 123678 C3-v0 1.86E-12 1.86E-12 1.94E-12 1.77E-12 1 4.51 5.10 0.33 

(continued) 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-11 

Table D-3b. Summary of Data for Emission Factor Development – Boilers Firing Fuel Oil 

(continued) 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Furan:6F 123789 C3-v0 2.50E-12 1.86E-12 3.88E-12 1.77E-12 1 47.67 53.94 0.00 

Furan:6F 234678 C3-v0 3.74E-12 3.88E-12 5.57E-12 1.77E-12 1 50.85 57.54 0.50 

Furan:7F 1234678 C3-v0 9.79E-12 7.76E-12 1.42E-11 7.43E-12 1 38.89 44.01 1.00 

Furan:7F 1234789 C3-v0 3.15E-12 1.86E-12 5.82E-12 1.77E-12 1 73.43 83.10 0.00 

Furan:8F C3-v0 4.86E-11 4.85E-11 7.06E-11 2.66E-11 1 45.27 51.23 1.00 

Indeno(1,2,3-cd)pyrene B3-v0 3.05E-09 2.28E-09 5.32E-09 1.97E-09 2 46.19 36.96 0.00 

Lead B3-v0 1.06E-05 5.84E-06 2.26E-05 3.32E-06 1 98.91 111.92 0.00 

Manganese B3-v0 3.95E-05 1.92E-05 8.29E-05 1.63E-05 1 95.34 107.89 1.00 

Mercury B3-v0 7.02E-08 6.15E-08 1.00E-07 4.89E-08 1 38.06 43.07 0.00 

2-Methylnaphthalene C3-v0 7.40E-08 7.25E-08 8.32E-08 6.63E-08 1 11.52 13.04 1.00 

Naphthalene B3-v0 4.04E-07 4.11E-07 5.52E-07 2.73E-07 2 28.11 22.49 1.00 

Nickel B3-v0 2.27E-03 2.08E-03 2.76E-03 1.97E-03 1 18.95 21.44 1.00 

Perylene C3-v0 7.44E-10 4.05E-10 1.49E-09 3.32E-10 1 87.56 99.09 0.00 

Phenanthrene B3-v0 7.39E-08 7.35E-08 1.35E-07 2.11E-08 2 60.02 48.02 1.00 

Propylene A3-v0 1.49E-04 1.50E-04 1.53E-04 1.44E-04 1 3.26 3.69 0.00 

Pyrene B3-v1 2.72E-08 1.58E-08 7.37E-08 2.26E-09 2 110.83 88.68 0.97 

Selenium B3-v0 1.96E-05 2.44E-05 2.45E-05 9.83E-06 1 43.13 48.81 0.17 

Toluene A3-v0 3.91E-05 3.94E-05 4.02E-05 3.77E-05 1 3.26 3.69 0.00 

Xylene (Total) A3-v0 7.51E-05 7.56E-05 7.72E-05 7.24E-05 1 3.26 3.69 0.00 

Zinc B3-v0 1.09E-04 5.86E-05 2.10E-04 5.82E-05 1 80.41 90.99 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-12 

Table D-4a. Summary of Data for Emission Factor Development – 

Boilers Firing Refinery Fuel Gas 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty,

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A3-v0 5.88E-06 5.75E-06 6.47E-06 5.44E-06 1 8.97 10.15 0.37 

Acenaphthylene A3-v0 2.56E-06 2.59E-06 2.59E-06 2.50E-06 1 2.04 2.31 0.00 

Acetaldehyde C1-v3 3.97E-03 2.43E-03 1.21E-02 4.92E-06 5 100.80 51.01 1.00 

Anthracene A3-v0 2.28E-05 2.50E-05 3.89E-05 4.40E-06 1 76.23 86.26 1.00 

Arsenic D3-v0 7.04E-04 7.65E-04 1.13E-03 2.11E-04 1 66.10 74.80 1.00 

Benzene C1-v2 2.06E-01 6.24E-02 1.40E+00 3.39E-03 5 180.67 88.53 0.80 

Benzo(a)anthracene A3-v0 1.83E-05 1.79E-05 2.46E-05 1.25E-05 1 33.08 37.44 1.00 

Benzo(a)pyrene A3-v0 3.42E-06 3.37E-06 4.40E-06 2.50E-06 1 27.72 31.36 0.76 

Benzo(b)fluoranthene A3-v0 6.76E-06 7.24E-06 8.28E-06 4.75E-06 1 26.90 30.44 1.00 

Benzo(g,h,i)perylene A3-v0 3.85E-06 3.89E-06 5.17E-06 2.50E-06 1 34.64 39.20 0.78 

Benzo(k)fluoranthene A3-v0 2.56E-06 2.59E-06 2.59E-06 2.50E-06 1 2.04 2.31 0.00 

Beryllium D3-v0 1.55E-04 1.55E-04 1.56E-04 1.53E-04 1 1.35 1.87 1.00 

Cadmium D3-v0 2.38E-03 2.05E-03 3.13E-03 1.98E-03 1 27.01 30.57 1.00 

Chromium (Hex) C3-v0 7.70E-03 7.56E-03 1.09E-02 4.67E-03 1 40.17 45.45 0.00 

Chromium (Total) C3-v1 1.28E-02 5.43E-03 3.08E-02 2.16E-03 1 122.51 138.63 1.00 

Chrysene A3-v0 3.42E-06 2.59E-06 5.17E-06 2.50E-06 1 44.30 50.13 0.50 

Copper D3-v0 6.30E-03 6.30E-03 7.71E-03 4.89E-03 1 31.59 43.78 1.00 

Dibenz(a,h)anthracene A3-v0 2.56E-06 2.59E-06 2.59E-06 2.50E-06 1 2.04 2.31 0.00 

Fluoranthene A3-v0 4.25E-05 3.10E-05 7.24E-05 2.40E-05 1 61.63 69.74 1.00 

Fluorene A3-v0 9.78E-06 5.75E-06 1.82E-05 5.44E-06 1 74.23 84.00 1.00 

Formaldehyde C1-v1 1.60E-02 1.41E-02 4.14E-02 3.24E-03 5 62.29 31.52 1.00 

Hydrogen Sulfide A1-v1 2.74E-01 2.37E-01 7.15E-01 5.94E-02 5 89.81 44.00 0.00 

Indeno(1,2,3-cd)pyrene A3-v0 2.56E-06 2.59E-06 2.59E-06 2.50E-06 1 2.04 2.31 0.00 

Lead D3-v0 2.42E-03 2.42E-03 2.49E-03 2.36E-03 1 3.87 5.36 1.00 

Manganese D3-v0 2.39E-03 2.39E-03 3.14E-03 1.64E-03 1 44.52 61.70 1.00 

Mercury D3-v0 3.23E-04 3.18E-04 3.82E-04 2.70E-04 1 17.33 19.60 0.00 

Naphthalene A3-v0 2.06E-04 1.94E-04 2.40E-04 1.85E-04 1 14.51 16.42 1.00 

Nickel D3-v0 5.59E-03 5.59E-03 7.03E-03 4.16E-03 1 36.33 50.35 1.00 

Phenanthrene A3-v0 5.64E-05 4.49E-05 8.80E-05 3.62E-05 1 49.24 55.72 1.00 

Phenol C2-v0 2.18E-03 8.64E-04 5.66E-03 7.28E-04 4 98.89 54.25 0.85 

Pyrene A3-v0 5.98E-05 5.17E-05 8.28E-05 4.49E-05 1 33.82 38.27 1.00 

Selenium D3-v0 2.06E-03 2.36E-03 2.83E-03 9.79E-04 1 46.79 52.94 0.16 

Toluene E2-v2 8.40E-01 8.35E-02 5.00E+00 4.14E-02 3 189.87 124.04 0.97 

Zinc D3-v2 3.42E+00 3.82E-01 9.78E+00 9.27E-02 1 161.24 182.45 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-13 

Table D-4b. Summary of Data for Emission Factor Development – 

Boilers Firing Refinery Fuel Gas 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A3-v0 4.90E-09 4.65E-09 5.46E-09 4.59E-09 1 9.89 11.20 0.37 

Acenaphthylene A3-v0 2.13E-09 2.19E-09 2.19E-09 2.02E-09 1 4.43 5.01 0.00 

Acetaldehyde C1-v3 3.01E-06 2.11E-06 1.01E-05 4.10E-09 5 95.45 48.30 1.00 

Anthracene A3-v0 1.89E-08 2.02E-08 3.28E-08 3.71E-09 1 77.14 87.30 1.00 

Arsenic D3-v0 5.88E-07 6.46E-07 9.40E-07 1.78E-07 1 65.36 73.95 1.00 

Benzene C1-v2 1.74E-04 5.03E-05 1.22E-03 2.86E-06 5 186.11 91.19 0.80 

Benzo(a)anthracene A3-v0 1.53E-08 1.51E-08 2.07E-08 1.01E-08 1 34.78 39.35 1.00 

Benzo(a)pyrene A3-v0 2.86E-09 2.84E-09 3.71E-09 2.02E-09 1 29.49 33.37 0.76 

Benzo(b)fluoranthene A3-v0 5.65E-09 6.11E-09 6.99E-09 3.84E-09 1 28.79 32.57 1.00 

Benzo(g,h,i)perylene A3-v0 3.22E-09 3.28E-09 4.36E-09 2.02E-09 1 36.33 41.11 0.78 

Benzo(k)fluoranthene A3-v0 2.13E-09 2.19E-09 2.19E-09 2.02E-09 1 4.43 5.01 0.00 

Beryllium D3-v0 1.31E-07 1.31E-07 1.32E-07 1.29E-07 1 1.35 1.87 1.00 

Cadmium D3-v0 2.00E-06 1.70E-06 2.64E-06 1.67E-06 1 27.60 31.23 1.00 

Chromium (Hex) C3-v0 6.32E-06 6.29E-06 8.78E-06 3.89E-06 1 38.70 43.79 0.00 

Chromium (Total) C3-v1 1.04E-05 4.51E-06 2.49E-05 1.80E-06 1 121.39 137.36 1.00 

Chrysene A3-v0 2.86E-09 2.19E-09 4.36E-09 2.02E-09 1 45.70 51.71 0.50 

Copper D3-v0 5.32E-06 5.32E-06 6.51E-06 4.13E-06 1 31.59 43.78 1.00 

Dibenz(a,h)anthracene A3-v0 2.13E-09 2.19E-09 2.19E-09 2.02E-09 1 4.43 5.01 0.00 

Fluoranthene A3-v0 3.56E-08 2.62E-08 6.11E-08 1.94E-08 1 62.95 71.23 1.00 

Fluorene A3-v0 8.19E-09 4.65E-09 1.53E-08 4.59E-09 1 75.53 85.46 1.00 

Formaldehyde C1-v1 1.32E-05 1.16E-05 3.62E-05 2.81E-06 5 66.84 33.82 1.00 

Hydrogen Sulfide A1-v1 2.21E-04 1.69E-04 5.93E-04 5.01E-05 5 92.80 45.47 0.00 

Indeno(1,2,3-cd)pyrene A3-v0 2.13E-09 2.19E-09 2.19E-09 2.02E-09 1 4.43 5.01 0.00 

Lead D3-v0 2.05E-06 2.05E-06 2.10E-06 1.99E-06 1 3.87 5.36 1.00 

Manganese D3-v0 2.02E-06 2.02E-06 2.65E-06 1.38E-06 1 44.52 61.70 1.00 

Mercury D3-v0 2.72E-07 2.69E-07 3.22E-07 2.24E-07 1 18.19 20.58 0.00 

Naphthalene A3-v0 1.72E-07 1.63E-07 2.03E-07 1.49E-07 1 16.13 18.25 1.00 

Nickel D3-v0 4.72E-06 4.72E-06 5.94E-06 3.51E-06 1 36.33 50.35 1.00 

Phenanthrene A3-v0 4.71E-08 3.63E-08 7.43E-08 3.06E-08 1 50.50 57.15 1.00 

Phenol C2-v0 1.83E-06 7.04E-07 4.91E-06 5.45E-07 4 99.84 56.49 0.85 

Pyrene A3-v0 5.00E-08 4.36E-08 6.99E-08 3.63E-08 1 35.35 40.00 1.00 

Selenium D3-v0 1.73E-06 1.99E-06 2.39E-06 8.11E-07 1 47.44 53.68 0.16 

Toluene E2-v2 7.23E-04 7.25E-05 4.37E-03 3.59E-05 3 193.00 126.09 0.97 

Zinc D3-v2 2.83E-03 3.22E-04 8.10E-03 7.83E-05 1 161.02 182.20 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-14 

Table D-5a. Summary of Data for Emission Factor Development – Boilers Firing Refinery 

Fuel Gas Controlled with Selective Catalytic Reduction (NOx) 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A3-v0 5.88E-06 5.75E-06 6.47E-06 5.44E-06 1 8.97 10.15 0.37 

Acenaphthylene A3-v0 2.56E-06 2.59E-06 2.59E-06 2.50E-06 1 2.04 2.31 0.00 

Acetaldehyde C1-v3 3.97E-03 2.43E-03 1.21E-02 4.92E-06 5 100.80 51.01 1.00 

Anthracene A3-v0 2.28E-05 2.50E-05 3.89E-05 4.40E-06 1 76.23 86.26 1.00 

Arsenic D3-v0 7.04E-04 7.65E-04 1.13E-03 2.11E-04 1 66.10 74.80 1.00 

Benzene C1-v2 2.06E-01 6.24E-02 1.40E+00 3.39E-03 5 180.67 88.53 0.80 

Benzo(a)anthracene A3-v0 1.83E-05 1.79E-05 2.46E-05 1.25E-05 1 33.08 37.44 1.00 

Benzo(a)pyrene A3-v0 3.42E-06 3.37E-06 4.40E-06 2.50E-06 1 27.72 31.36 0.76 

Benzo(b)fluoranthene A3-v0 6.76E-06 7.24E-06 8.28E-06 4.75E-06 1 26.90 30.44 1.00 

Benzo(g,h,i)perylene A3-v0 3.85E-06 3.89E-06 5.17E-06 2.50E-06 1 34.64 39.20 0.78 

Benzo(k)fluoranthene A3-v0 2.56E-06 2.59E-06 2.59E-06 2.50E-06 1 2.04 2.31 0.00 

Beryllium D3-v0 1.55E-04 1.55E-04 1.56E-04 1.53E-04 1 1.35 1.87 1.00 

Cadmium D3-v0 2.38E-03 2.05E-03 3.13E-03 1.98E-03 1 27.01 30.57 1.00 

Chromium (Hex) C3-v0 7.70E-03 7.56E-03 1.09E-02 4.67E-03 1 40.17 45.45 0.00 

Chromium (Total) C3-v1 1.28E-02 5.43E-03 3.08E-02 2.16E-03 1 122.51 138.63 1.00 

Chrysene A3-v0 3.42E-06 2.59E-06 5.17E-06 2.50E-06 1 44.30 50.13 0.50 

Copper D3-v0 6.30E-03 6.30E-03 7.71E-03 4.89E-03 1 31.59 43.78 1.00 

Dibenz(a,h)anthracene A3-v0 2.56E-06 2.59E-06 2.59E-06 2.50E-06 1 2.04 2.31 0.00 

Fluoranthene A3-v0 4.25E-05 3.10E-05 7.24E-05 2.40E-05 1 61.63 69.74 1.00 

Fluorene A3-v0 9.78E-06 5.75E-06 1.82E-05 5.44E-06 1 74.23 84.00 1.00 

Formaldehyde C1-v1 1.60E-02 1.41E-02 4.14E-02 3.24E-03 5 62.29 31.52 1.00 

Hydrogen Sulfide A1-v1 2.74E-01 2.37E-01 7.15E-01 5.94E-02 5 89.81 44.00 0.00 

Indeno(1,2,3-cd)pyrene A3-v0 2.56E-06 2.59E-06 2.59E-06 2.50E-06 1 2.04 2.31 0.00 

Lead D3-v0 2.42E-03 2.42E-03 2.49E-03 2.36E-03 1 3.87 5.36 1.00 

Manganese D3-v0 2.39E-03 2.39E-03 3.14E-03 1.64E-03 1 44.52 61.70 1.00 

Mercury D3-v0 3.23E-04 3.18E-04 3.82E-04 2.70E-04 1 17.33 19.60 0.00 

Naphthalene A3-v0 2.06E-04 1.94E-04 2.40E-04 1.85E-04 1 14.51 16.42 1.00 

Nickel D3-v0 5.59E-03 5.59E-03 7.03E-03 4.16E-03 1 36.33 50.35 1.00 

Phenanthrene A3-v0 5.64E-05 4.49E-05 8.80E-05 3.62E-05 1 49.24 55.72 1.00 

Phenol C2-v0 2.18E-03 8.64E-04 5.66E-03 7.28E-04 4 95.89 54.25 0.85 

Pyrene A3-v0 5.98E-05 5.17E-05 8.28E-05 4.49E-05 1 33.82 38.27 1.00 

Selenium D3-v0 2.06E-03 2.36E-03 2.83E-03 9.79E-04 1 46.79 52.94 0.16 

Toluene E2-v2 8.40E-01 8.35E-02 5.00E+00 4.14E-02 3 189.87 124.04 0.97 

Zinc D3-v2 3.42E+00 3.82E-01 9.78E+00 9.27E-02 1 161.24 182.45 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-15 

Table D-5b. Summary of Data for Emission Factor Development – Boilers Firing Refinery 

Fuel Gas Controlled with Selective Catalytic Reduction (NOx) 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A3-v0 4.90E-09 4.65E-09 5.46E-09 4.59E-09 1 9.89 11.20 0.37 

Acenaphthylene A3-v0 2.13E-09 2.19E-09 2.19E-09 2.02E-09 1 4.43 5.01 0.00 

Acetaldehyde C1-v3 3.01E-06 2.11E-06 1.01E-05 4.10E-09 5 95.45 48.30 1.00 

Anthracene A3-v0 1.89E-08 2.02E-08 3.28E-08 3.71E-09 1 77.14 87.30 1.00 

Arsenic D3-v0 5.88E-07 6.46E-07 9.40E-07 1.78E-07 1 65.36 73.95 1.00 

Benzene C1-v2 1.74E-04 5.03E-05 1.22E-03 2.86E-06 5 186.11 91.19 0.80 

Benzo(a)anthracene A3-v0 1.53E-08 1.51E-08 2.07E-08 1.01E-08 1 34.78 39.35 1.00 

Benzo(a)pyrene A3-v0 2.86E-09 2.84E-09 3.71E-09 2.02E-09 1 29.49 33.37 0.76 

Benzo(b)fluoranthene A3-v0 5.65E-09 6.11E-09 6.99E-09 3.84E-09 1 28.79 32.57 1.00 

Benzo(g,h,i)perylene A3-v0 3.22E-09 3.28E-09 4.36E-09 2.02E-09 1 36.33 41.11 0.78 

Benzo(k)fluoranthene A3-v0 2.13E-09 2.19E-09 2.19E-09 2.02E-09 1 4.43 5.01 0.00 

Beryllium D3-v0 1.31E-07 1.31E-07 1.32E-07 1.29E-07 1 1.35 1.87 1.00 

Cadmium D3-v0 2.00E-06 1.70E-06 2.64E-06 1.67E-06 1 27.60 31.23 1.00 

Chromium (Hex) C3-v0 6.32E-06 6.29E-06 8.78E-06 3.89E-06 1 38.70 43.79 0.00 

Chromium (Total) C3-v1 1.04E-05 4.51E-06 2.49E-05 1.80E-06 1 121.39 137.36 1.00 

Chrysene A3-v0 2.86E-09 2.19E-09 4.36E-09 2.02E-09 1 45.70 51.71 0.50 

Copper D3-v0 5.32E-06 5.32E-06 6.51E-06 4.13E-06 1 31.59 43.78 1.00 

Dibenz(a,h)anthracene A3-v0 2.13E-09 2.19E-09 2.19E-09 2.02E-09 1 4.43 5.01 0.00 

Fluoranthene A3-v0 3.56E-08 2.62E-08 6.11E-08 1.94E-08 1 62.95 71.23 1.00 

Fluorene A3-v0 8.19E-09 4.65E-09 1.53E-08 4.59E-09 1 75.53 85.46 1.00 

Formaldehyde C1-v1 1.32E-05 1.16E-05 3.62E-05 2.81E-06 5 66.84 33.82 1.00 

Hydrogen Sulfide A1-v1 2.21E-04 1.69E-04 5.93E-04 5.01E-05 5 92.80 45.47 0.00 

Indeno(1,2,3-cd)pyrene A3-v0 2.13E-09 2.19E-09 2.19E-09 2.02E-09 1 4.43 5.01 0.00 

Lead D3-v0 2.05E-06 2.05E-06 2.10E-06 1.99E-06 1 3.87 5.36 1.00 

Manganese D3-v0 2.02E-06 2.02E-06 2.65E-06 1.38E-06 1 44.52 61.70 1.00 

Mercury D3-v0 2.72E-07 2.69E-07 3.22E-07 2.24E-07 1 18.19 20.58 0.00 

Naphthalene A3-v0 1.72E-07 1.63E-07 2.03E-07 1.49E-07 1 16.13 18.25 1.00 

Nickel D3-v0 4.72E-06 4.72E-06 5.94E-06 3.51E-06 1 36.33 50.35 1.00 

Phenanthrene A3-v0 4.71E-08 3.63E-08 7.43E-08 3.06E-08 1 50.50 57.15 1.00 

Phenol C2-v0 1.83E-06 7.04E-07 4.91E-06 5.45E-07 4 99.84 56.49 0.85 

Pyrene A3-v0 5.00E-08 4.36E-08 6.99E-08 3.63E-08 1 35.35 40.00 1.00 

Selenium D3-v0 1.73E-06 1.99E-06 2.39E-06 8.11E-07 1 47.44 53.68 0.16 

Toluene E2-v2 7.23E-04 7.25E-05 4.37E-03 3.59E-05 3 193.00 126.09 0.97 

Zinc D3-v2 2.83E-03 3.22E-04 8.10E-03 7.83E-05 1 161.02 182.20 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-16 

Table D-6a. Summary of Data for Emission Factor Development – 

Coke Calcining Controlled by Spray Dryer and Fabric Filter 

Substance 

CARB 

Rating 

Emission Factor (lb/ton coke) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A3-v0 1.46E-08 1.38E-08 1.64E-08 1.37E-08 1 10.68 12.08 1.00 

Acenaphthylene A3-v0 1.83E-08 1.69E-08 2.81E-08 9.87E-09 1 50.39 57.02 1.00 

Acetaldehyde A3-v0 1.02E-03 1.16E-03 1.22E-03 6.77E-04 1 29.23 33.07 1.00 

Acrolein A3-v0 3.36E-04 3.41E-04 3.60E-04 3.08E-04 1 7.79 8.82 0.00 

Anthracene A3-v0 1.82E-08 1.84E-08 1.97E-08 1.64E-08 1 9.02 10.20 1.00 

Antimony C3-v0 4.61E-05 4.64E-05 4.79E-05 4.41E-05 1 4.04 4.57 0.34 

Arsenic C3-v0 4.66E-06 4.64E-06 4.92E-06 4.41E-06 1 5.42 6.13 0.00 

Barium C3-v0 1.95E-05 1.99E-05 2.46E-05 1.39E-05 1 27.51 31.13 1.00 

Benzene C3-v0 3.24E-04 4.06E-04 4.50E-04 1.15E-04 1 56.20 63.60 1.00 

Benzo(a)anthracene A3-v0 8.71E-09 8.25E-09 1.02E-08 7.67E-09 1 15.15 17.15 0.39 

Benzo(a)pyrene A3-v0 8.05E-09 8.22E-09 8.25E-09 7.67E-09 1 4.04 4.57 0.00 

Benzo(b)fluoranthene A3-v0 8.05E-09 8.22E-09 8.25E-09 7.67E-09 1 4.04 4.57 0.00 

Benzo(g,h,i)perylene A3-v0 8.05E-09 8.22E-09 8.25E-09 7.67E-09 1 4.04 4.57 0.00 

Benzo(k)fluoranthene A3-v0 8.05E-09 8.22E-09 8.25E-09 7.67E-09 1 4.04 4.57 0.00 

Beryllium C3-v0 1.93E-06 1.72E-06 2.43E-06 1.63E-06 1 22.77 25.76 0.42 

Cadmium C3-v0 9.32E-06 9.27E-06 9.84E-06 8.84E-06 1 5.34 6.04 0.00 

Chromium (Hex) C3-v0 6.31E-07 6.30E-07 7.17E-07 5.45E-07 1 13.63 15.42 1.00 

Chromium (Total) C3-v0 2.05E-05 2.04E-05 2.09E-05 2.01E-05 1 1.82 2.06 1.00 

Chrysene A3-v0 1.28E-08 1.18E-08 1.84E-08 8.25E-09 1 40.02 45.28 0.79 

Copper C3-v0 9.32E-06 9.27E-06 9.84E-06 8.84E-06 1 5.34 6.04 0.00 

Dibenz(a,h)anthracene A3-v0 8.05E-09 8.22E-09 8.25E-09 7.67E-09 1 4.04 4.57 0.00 

Dioxin:4D 2378 A3-v0 1.14E-11 1.18E-11 1.32E-11 9.05E-12 1 18.56 21.00 0.00 

Dioxin:4D Other A3-v0 1.44E-10 1.01E-10 2.99E-10 3.17E-11 1 96.53 109.23 1.00 

Dioxin:5D 12378 A3-v0 9.56E-12 9.20E-12 1.35E-11 6.01E-12 1 39.05 44.19 0.00 

Dioxin:5D Other A3-v0 8.45E-11 8.83E-11 1.02E-10 6.34E-11 1 23.10 26.14 0.40 

Dioxin:6D 123478 A3-v0 9.93E-12 9.24E-12 1.57E-11 4.83E-12 1 55.10 62.35 0.31 

Dioxin:6D 123678 A3-v0 1.38E-11 1.27E-11 2.04E-11 8.30E-12 1 44.48 50.33 0.69 

Dioxin:6D 123789 A3-v0 1.29E-11 1.45E-11 1.50E-11 9.20E-12 1 24.83 28.10 0.39 

Dioxin:6D Other A3-v0 6.36E-11 6.71E-11 8.96E-11 3.39E-11 1 44.09 49.89 0.65 

Dioxin:7D 1234678 A3-v0 1.38E-10 1.18E-10 2.18E-10 7.96E-11 1 51.62 58.41 1.00 

Dioxin:7D Other A3-v0 1.32E-10 1.09E-10 1.90E-10 9.72E-11 1 38.24 43.27 1.00 

Dioxin:8D A3-v0 1.77E-09 1.79E-09 2.76E-09 7.60E-10 1 56.40 63.82 1.00 

Fluoranthene A3-v0 3.58E-08 3.30E-08 4.30E-08 3.13E-08 1 17.64 19.96 1.00 

Fluorene A3-v0 5.64E-08 5.21E-08 6.61E-08 5.10E-08 1 14.90 16.86 1.00 

Formaldehyde A3-v0 3.36E-04 3.41E-04 3.60E-04 3.08E-04 1 7.79 8.82 0.00 

Furan:4F 2378 A3-v0 1.33E-11 1.19E-11 1.63E-11 1.18E-11 1 19.13 21.65 0.70 

Furan:4F Other A3-v0 1.39E-10 1.10E-10 2.15E-10 9.21E-11 1 47.70 53.98 1.00 

Furan:5F 12378 A3-v0 1.36E-11 1.43E-11 1.50E-11 1.16E-11 1 13.01 14.72 0.65 

(continued) 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-17 

Table D-6a. Summary of Data for Emission Factor Development – 

Coke Calcining Controlled by Spray Dryer and Fabric Filter (continued) 

Substance 

CARB 

Rating 

Emission Factor (lb/ton coke) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Furan:5F 23478 A3-v0 1.25E-11 1.38E-11 1.46E-11 9.10E-12 1 23.87 27.01 0.63 

Furan:5F Other A3-v0 1.20E-10 9.47E-11 1.79E-10 8.70E-11 1 42.57 48.17 0.74 

Furan:6F 123478 A3-v0 2.44E-11 2.49E-11 2.71E-11 2.12E-11 1 12.27 13.89 1.00 

Furan:6F 123678 A3-v0 2.21E-11 2.19E-11 3.13E-11 1.31E-11 1 41.02 46.42 1.00 

Furan:6F 123789 A3-v0 9.19E-12 8.96E-12 1.20E-11 6.64E-12 1 29.03 32.85 0.67 

Furan:6F 234678 A3-v0 2.01E-11 2.04E-11 2.04E-11 1.96E-11 1 2.55 2.88 1.00 

Furan:6F Other A3-v0 1.52E-10 1.31E-10 2.36E-10 9.04E-11 1 49.18 55.66 1.00 

Furan:7F 1234678 A3-v0 1.50E-10 1.42E-10 1.76E-10 1.32E-10 1 15.51 17.55 1.00 

Furan:7F 1234789 A3-v0 2.56E-11 2.56E-11 2.99E-11 2.12E-11 1 17.09 19.33 0.72 

Furan:7F Other A3-v0 5.16E-11 5.16E-11 5.16E-11 5.16E-11 1 0.00 0.00 0.50 

Furan:8F A3-v1 1.46E-10 1.36E-10 2.86E-10 1.61E-11 1 92.60 104.78 1.00 

Indeno(1,2,3-cd)pyrene A3-v0 8.05E-09 8.22E-09 8.25E-09 7.67E-09 1 4.04 4.57 0.00 

Lead C3-v0 6.20E-05 4.92E-05 9.27E-05 4.41E-05 1 43.08 48.75 0.50 

Manganese C3-v0 4.56E-05 4.41E-05 7.63E-05 1.63E-05 1 65.87 74.54 0.88 

Mercury C3-v1 4.63E-05 1.63E-05 1.12E-04 1.08E-05 1 122.58 138.71 1.00 

Naphthalene A3-v0 2.41E-06 2.46E-06 3.14E-06 1.64E-06 1 31.02 35.10 1.00 

Nickel C3-v0 9.06E-05 4.92E-05 1.76E-04 4.64E-05 1 81.90 92.67 0.65 

Phenanthrene A3-v0 1.88E-07 1.81E-07 2.15E-07 1.69E-07 1 12.67 14.34 1.00 

Phosphorus C3-v0 4.66E-04 4.64E-04 4.92E-04 4.41E-04 1 5.42 6.13 0.00 

Pyrene A3-v0 2.67E-08 2.64E-08 3.23E-08 2.15E-08 1 20.27 22.94 1.00 

Selenium C3-v0 4.66E-06 4.64E-06 4.92E-06 4.41E-06 1 5.42 6.13 0.00 

Silver C3-v0 1.63E-05 1.63E-05 1.72E-05 1.54E-05 1 5.45 6.17 0.00 

Thallium C3-v0 6.99E-05 6.96E-05 7.38E-05 6.64E-05 1 5.31 6.01 0.00 

Toluene C3-v0 5.34E-05 4.46E-05 7.17E-05 4.39E-05 1 29.73 33.64 1.00 

Xylene (m,p) C3-v0 3.09E-05 3.44E-05 3.79E-05 2.04E-05 1 29.89 33.82 0.22 

Xylene (o) C3-v0 4.49E-05 4.34E-05 4.79E-05 4.34E-05 1 5.72 6.47 0.00 

Zinc C3-v0 1.17E-04 1.04E-04 1.63E-04 8.37E-05 1 35.15 39.78 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-18 

Table D-6b. Summary of Data for Emission Factor Development – 

Coke Calcining Controlled by Spray Dryer and Fabric Filter 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A3-v0 4.40E-08 4.06E-08 5.43E-08 3.70E-08 1 20.68 23.40 1.00 

Acenaphthylene A3-v0 5.59E-08 4.58E-08 9.29E-08 2.90E-08 1 59.27 67.06 1.00 

Acetaldehyde A3-v0 3.12E-03 3.14E-03 3.89E-03 2.33E-03 1 24.96 28.25 1.00 

Acrolein A3-v0 1.04E-03 1.06E-03 1.14E-03 9.25E-04 1 10.62 12.02 0.00 

Anthracene A3-v0 5.40E-08 5.43E-08 5.79E-08 4.98E-08 1 7.50 8.48 1.00 

Antimony C3-v0 1.44E-04 1.42E-04 1.52E-04 1.37E-04 1 5.19 5.87 0.34 

Arsenic C3-v0 1.45E-05 1.42E-05 1.56E-05 1.37E-05 1 6.73 7.62 0.00 

Barium C3-v0 6.10E-05 6.40E-05 7.79E-05 4.11E-05 1 30.51 34.52 1.00 

Benzene C3-v0 1.03E-03 1.39E-03 1.45E-03 2.62E-04 1 64.73 73.25 1.00 

Benzo(a)anthracene A3-v0 2.60E-08 2.72E-08 2.99E-08 2.08E-08 1 18.05 20.43 0.39 

Benzo(a)pyrene A3-v0 2.41E-08 2.42E-08 2.72E-08 2.08E-08 1 13.35 15.10 0.00 

Benzo(b)fluoranthene A3-v0 2.41E-08 2.42E-08 2.72E-08 2.08E-08 1 13.35 15.10 0.00 

Benzo(g,h,i)perylene A3-v0 2.41E-08 2.42E-08 2.72E-08 2.08E-08 1 13.35 15.10 0.00 

Benzo(k)fluoranthene A3-v0 2.41E-08 2.42E-08 2.72E-08 2.08E-08 1 13.35 15.10 0.00 

Beryllium C3-v0 6.03E-06 5.45E-06 7.83E-06 4.81E-06 1 26.41 29.88 0.42 

Cadmium C3-v0 2.90E-05 2.85E-05 3.12E-05 2.74E-05 1 6.71 7.59 0.00 

Chromium (Hex) C3-v0 2.12E-06 1.93E-06 2.88E-06 1.54E-06 1 32.38 36.64 1.00 

Chromium (Total) C3-v0 6.90E-05 5.92E-05 9.35E-05 5.44E-05 1 30.92 34.99 1.00 

Chrysene A3-v0 3.73E-08 3.48E-08 4.98E-08 2.72E-08 1 30.84 34.90 0.79 

Copper C3-v0 2.90E-05 2.85E-05 3.12E-05 2.74E-05 1 6.71 7.59 0.00 

Dibenz(a,h)anthracene A3-v0 2.41E-08 2.42E-08 2.72E-08 2.08E-08 1 13.35 15.10 0.00 

Dioxin:4D 2378 A3-v0 3.68E-11 3.66E-11 4.86E-11 2.51E-11 1 31.88 36.08 0.00 

Dioxin:4D Other A3-v0 4.44E-10 4.14E-10 8.31E-10 8.81E-11 1 83.85 94.88 1.00 

Dioxin:5D 12378 A3-v0 2.92E-11 2.56E-11 3.74E-11 2.47E-11 1 24.24 27.43 0.00 

Dioxin:5D Other A3-v0 2.74E-10 2.83E-10 3.63E-10 1.76E-10 1 34.15 38.64 0.40 

Dioxin:6D 123478 A3-v0 3.45E-11 2.57E-11 6.45E-11 1.34E-11 1 77.21 87.37 0.31 

Dioxin:6D 123678 A3-v0 4.40E-11 5.23E-11 5.68E-11 2.30E-11 1 41.59 47.07 0.69 

Dioxin:6D 123789 A3-v0 4.22E-11 4.16E-11 5.95E-11 2.56E-11 1 40.22 45.52 0.39 

Dioxin:6D Other A3-v0 2.06E-10 2.49E-10 2.76E-10 9.42E-11 1 47.47 53.72 0.65 

Dioxin:7D 1234678 A3-v0 4.19E-10 3.27E-10 6.05E-10 3.27E-10 1 38.30 43.34 1.00 

Dioxin:7D Other A3-v0 4.09E-10 3.99E-10 5.27E-10 3.02E-10 1 27.59 31.22 1.00 

Dioxin:8D A3-v0 5.25E-09 4.98E-09 7.65E-09 3.12E-09 1 43.40 49.11 1.00 

Fluoranthene A3-v0 1.06E-07 1.09E-07 1.16E-07 9.18E-08 1 11.95 13.52 1.00 

Fluorene A3-v0 1.70E-07 1.50E-07 2.18E-07 1.41E-07 1 24.78 28.04 1.00 

Formaldehyde A3-v0 1.04E-03 1.06E-03 1.14E-03 9.25E-04 1 10.62 12.02 0.00 

Furan:4F 2378 A3-v0 4.23E-11 4.53E-11 4.85E-11 3.31E-11 1 19.19 21.72 0.70 

Furan:4F Other A3-v0 4.35E-10 4.51E-10 5.97E-10 2.56E-10 1 39.34 44.51 1.00 

(continued) 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-19 

Table D-6b. Summary of Data for Emission Factor Development – 

Coke Calcining Controlled by Spray Dryer and Fabric Filter (continued) 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Furan:5F 12378 A3-v0 4.42E-11 4.16E-11 5.87E-11 3.23E-11 1 30.36 34.35 0.65 

Furan:5F 23478 A3-v0 4.09E-11 4.07E-11 5.66E-11 2.53E-11 1 38.39 43.44 0.63 

Furan:5F Other A3-v0 3.76E-10 3.89E-10 4.98E-10 2.42E-10 1 34.21 38.71 0.74 

Furan:6F 123478 A3-v0 7.88E-11 7.53E-11 1.02E-10 5.88E-11 1 27.77 31.43 1.00 

Furan:6F 123678 A3-v0 7.11E-11 8.68E-11 9.00E-11 3.65E-11 1 42.25 47.81 1.00 

Furan:6F 123789 A3-v0 2.95E-11 3.32E-11 3.68E-11 1.84E-11 1 33.01 37.36 0.67 

Furan:6F 234678 A3-v0 6.50E-11 5.68E-11 8.39E-11 5.43E-11 1 25.28 28.60 1.00 

Furan:6F Other A3-v0 4.81E-10 5.38E-10 6.54E-10 2.51E-10 1 43.15 48.82 1.00 

Furan:7F 1234678 A3-v0 4.75E-10 4.90E-10 5.42E-10 3.94E-10 1 15.81 17.89 1.00 

Furan:7F 1234789 A3-v0 8.04E-11 8.31E-11 8.70E-11 7.12E-11 1 10.23 11.58 0.72 

Furan:7F Other A3-v0 1.77E-10 1.77E-10 2.12E-10 1.43E-10 1 27.28 37.81 0.50 

Furan:8F A3-v1 4.13E-10 3.77E-10 7.94E-10 6.63E-11 1 88.52 100.16 1.00 

Indeno(1,2,3-cd)pyrene A3-v0 2.41E-08 2.42E-08 2.72E-08 2.08E-08 1 13.35 15.10 0.00 

Lead C3-v0 1.91E-04 1.56E-04 2.74E-04 1.42E-04 1 37.94 42.93 0.50 

Manganese C3-v0 1.44E-04 1.42E-04 2.42E-04 4.81E-05 1 67.22 76.06 0.88 

Mercury C3-v1 1.48E-04 4.81E-05 3.60E-04 3.43E-05 1 124.89 141.33 1.00 

Naphthalene A3-v0 7.29E-06 6.67E-06 1.04E-05 4.83E-06 1 38.67 43.75 1.00 

Nickel C3-v0 2.87E-04 1.56E-04 5.68E-04 1.37E-04 1 84.93 96.10 0.65 

Phenanthrene A3-v0 5.66E-07 5.31E-07 7.09E-07 4.58E-07 1 22.80 25.80 1.00 

Phosphorus C3-v0 1.45E-03 1.42E-03 1.56E-03 1.37E-03 1 6.73 7.62 0.00 

Pyrene A3-v0 7.86E-08 7.75E-08 8.76E-08 7.09E-08 1 10.68 12.09 1.00 

Selenium C3-v0 1.45E-05 1.42E-05 1.56E-05 1.37E-05 1 6.73 7.62 0.00 

Silver C3-v0 5.07E-05 4.97E-05 5.45E-05 4.81E-05 1 6.52 7.37 0.00 

Thallium C3-v0 2.18E-04 2.14E-04 2.34E-04 2.06E-04 1 6.65 7.53 0.00 

Toluene C3-v0 1.63E-04 1.44E-04 2.45E-04 9.97E-05 1 45.82 51.85 1.00 

Xylene (m,p) C3-v0 8.90E-05 8.62E-05 1.11E-04 6.99E-05 1 23.14 26.18 0.22 

Xylene (o) C3-v0 1.32E-04 1.40E-04 1.48E-04 1.09E-04 1 15.78 17.86 0.00 

Zinc C3-v0 3.66E-04 3.08E-04 5.25E-04 2.65E-04 1 38.08 43.10 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-20 

Table D-7a. Summary of Data for Emission Factor Development – Heaters Firing Natural Gas 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A3-v0 1.39E-06 1.40E-06 1.62E-06 1.15E-06 1 16.72 18.92 0.72 

Acenaphthylene A3-v1 1.21E-05 2.84E-06 3.23E-05 1.15E-06 1 144.82 163.88 0.97 

Acetaldehyde A3-v0 4.61E-03 4.61E-03 4.82E-03 4.41E-03 1 4.47 5.06 0.32 

Acrolein A3-v0 4.51E-03 4.56E-03 4.64E-03 4.32E-03 1 3.66 4.14 0.00 

Anthracene A3-v0 1.61E-06 1.83E-06 1.85E-06 1.15E-06 1 24.62 27.86 0.76 

Benzene A3-v0 2.34E-03 1.65E-03 3.71E-03 1.65E-03 1 50.72 57.40 0.53 

Benzo(a)anthracene A3-v0 1.41E-06 1.18E-06 1.90E-06 1.15E-06 1 29.86 33.79 0.45 

Benzo(a)pyrene A3-v0 1.14E-06 1.15E-06 1.18E-06 1.08E-06 1 4.76 5.39 0.00 

Benzo(b)fluoranthene A3-v0 1.14E-06 1.15E-06 1.18E-06 1.08E-06 1 4.76 5.39 0.00 

Benzo(g,h,i)perylene A3-v0 1.25E-06 1.18E-06 1.42E-06 1.15E-06 1 11.81 13.36 0.38 

Benzo(k)fluoranthene A3-v0 1.14E-06 1.15E-06 1.18E-06 1.08E-06 1 4.76 5.39 0.00 

Chrysene A3-v0 1.39E-06 1.18E-06 1.83E-06 1.15E-06 1 27.63 31.27 0.44 

Dibenz(a,h)anthracene A3-v0 1.14E-06 1.15E-06 1.18E-06 1.08E-06 1 4.76 5.39 0.00 

Ethylbenzene A3-v0 2.25E-03 2.25E-03 2.25E-03 2.25E-03 1 0.00 0.00 0.00 

Fluoranthene A3-v0 1.19E-05 1.07E-05 1.79E-05 7.15E-06 1 46.07 52.14 1.00 

Fluorene A3-v0 4.59E-06 4.50E-06 5.82E-06 3.46E-06 1 25.79 29.19 1.00 

Formaldehyde A3-v0 4.75E-03 4.61E-03 5.32E-03 4.32E-03 1 10.76 12.18 0.37 

Indeno(1,2,3-cd)pyrene A3-v0 1.14E-06 1.15E-06 1.18E-06 1.08E-06 1 4.76 5.39 0.00 

Naphthalene A3-v0 2.37E-04 2.37E-04 2.80E-04 1.94E-04 1 18.28 20.69 1.00 

Phenanthrene A3-v0 3.37E-05 3.31E-05 4.74E-05 2.05E-05 1 39.96 45.22 1.00 

Propylene A3-v0 4.63E-01 4.57E-01 6.13E-01 3.20E-01 1 31.59 35.74 1.00 

Pyrene A3-v0 5.60E-06 2.84E-06 1.16E-05 2.31E-06 1 93.70 106.03 1.00 

Toluene A3-v0 3.23E-02 1.38E-02 7.47E-02 8.37E-03 1 114.08 129.09 1.00 

Xylene (Total) A3-v0 1.87E-02 2.05E-02 2.97E-02 5.71E-03 1 64.92 73.46 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-21 

Table D-7b. Summary of Data for Emission Factor Development – Heaters Firing Natural Gas 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A3-v0 1.36E-09 1.36E-09 1.58E-09 1.13E-09 1 16.72 18.92 0.72 

Acenaphthylene A3-v1 1.18E-08 2.77E-09 3.16E-08 1.13E-09 1 144.82 163.88 0.97 

Acetaldehyde A3-v0 4.50E-06 4.50E-06 4.71E-06 4.30E-06 1 4.47 5.06 0.32 

Acrolein A3-v0 4.40E-06 4.46E-06 4.53E-06 4.22E-06 1 3.66 4.14 0.00 

Anthracene A3-v0 1.57E-09 1.79E-09 1.80E-09 1.13E-09 1 24.62 27.86 0.76 

Benzene A3-v0 2.28E-06 1.61E-06 3.62E-06 1.61E-06 1 50.72 57.40 0.53 

Benzo(a)anthracene A3-v0 1.38E-09 1.16E-09 1.85E-09 1.13E-09 1 29.86 33.79 0.45 

Benzo(a)pyrene A3-v0 1.11E-09 1.13E-09 1.16E-09 1.05E-09 1 4.76 5.39 0.00 

Benzo(b)fluoranthene A3-v0 1.11E-09 1.13E-09 1.16E-09 1.05E-09 1 4.76 5.39 0.00 

Benzo(g,h,i)perylene A3-v0 1.22E-09 1.16E-09 1.39E-09 1.13E-09 1 11.81 13.36 0.38 

Benzo(k)fluoranthene A3-v0 1.11E-09 1.13E-09 1.16E-09 1.05E-09 1 4.76 5.39 0.00 

Chrysene A3-v0 1.36E-09 1.16E-09 1.79E-09 1.13E-09 1 27.63 31.27 0.44 

Dibenz(a,h)anthracene A3-v0 1.11E-09 1.13E-09 1.16E-09 1.05E-09 1 4.76 5.39 0.00 

Ethylbenzene A3-v0 2.20E-06 2.20E-06 2.20E-06 2.20E-06 1 0.00 0.00 0.00 

Fluoranthene A3-v0 1.16E-08 1.04E-08 1.75E-08 6.98E-09 1 46.07 52.14 1.00 

Fluorene A3-v0 4.49E-09 4.39E-09 5.69E-09 3.38E-09 1 25.79 29.19 1.00 

Formaldehyde A3-v0 4.64E-06 4.50E-06 5.19E-06 4.22E-06 1 10.76 12.18 0.37 

Indeno(1,2,3-cd)pyrene A3-v0 1.11E-09 1.13E-09 1.16E-09 1.05E-09 1 4.76 5.39 0.00 

Naphthalene A3-v0 2.31E-07 2.31E-07 2.74E-07 1.89E-07 1 18.28 20.69 1.00 

Phenanthrene A3-v0 3.29E-08 3.24E-08 4.63E-08 2.00E-08 1 39.96 45.22 1.00 

Propylene A3-v0 4.53E-04 4.47E-04 5.98E-04 3.13E-04 1 31.59 35.74 1.00 

Pyrene A3-v0 5.47E-09 2.77E-09 1.14E-08 2.25E-09 1 93.70 106.03 1.00 

Toluene A3-v0 3.15E-05 1.35E-05 7.29E-05 8.17E-06 1 114.08 129.09 1.00 

Xylene (Total) A3-v0 1.82E-05 2.01E-05 2.90E-05 5.58E-06 1 64.92 73.46 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-22 

Table D-8a. Summary of Data for Emission Factor Development – 

Heaters Firing Natural Gas and Refinery Fuel Gas 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty,

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A3-v0 7.53E-06 2.44E-06 1.81E-05 2.05E-06 1 121.63 137.64 1.00 

Acenaphthylene A3-v1 5.88E-05 2.32E-06 1.72E-04 2.11E-06 1 166.69 188.62 1.00 

Acetaldehyde C3-v0 1.47E-02 1.43E-02 1.67E-02 1.30E-02 1 12.83 14.52 1.00 

Acrolein C3-v0 2.29E-03 2.10E-03 2.84E-03 1.93E-03 1 21.23 24.03 0.00 

Anthracene A3-v0 1.04E-05 8.97E-06 1.43E-05 7.89E-06 1 33.12 37.48 1.00 

Benzene A3-v0 2.12E-02 1.99E-02 2.44E-02 1.94E-02 1 13.02 14.73 0.00 

Benzo(a)anthracene A3-v0 9.57E-06 7.66E-06 1.67E-05 4.34E-06 1 66.91 75.72 1.00 

Benzo(a)pyrene A3-v1 6.07E-06 6.67E-06 1.10E-05 5.25E-07 1 86.79 98.21 0.97 

Benzo(b)fluoranthene A3-v0 2.63E-06 1.91E-06 4.19E-06 1.79E-06 1 51.36 58.12 1.00 

Benzo(g,h,i)perylene A3-v0 4.13E-07 1.59E-07 9.55E-07 1.25E-07 1 113.74 128.71 0.77 

Benzo(k)fluoranthene A3-v0 1.46E-06 8.35E-07 3.18E-06 3.70E-07 1 103.06 116.62 0.92 

Chrysene A3-v0 7.91E-07 6.38E-07 1.24E-06 4.91E-07 1 50.32 56.94 0.52 

Dibenz(a,h)anthracene A3-v0 1.38E-07 1.07E-07 2.08E-07 1.01E-07 1 43.36 49.06 0.00 

Fluoranthene A3-v0 1.80E-05 1.03E-05 3.82E-05 5.49E-06 1 98.02 110.92 1.00 

Fluorene A3-v1 6.48E-04 1.50E-04 1.69E-03 1.01E-04 1 139.64 158.01 1.00 

Formaldehyde C3-v0 4.33E-02 2.38E-02 8.89E-02 1.73E-02 1 91.33 103.35 1.00 

Indeno(1,2,3-

cd)pyrene A3-v0 4.56E-07 4.04E-07 6.67E-07 2.96E-07 1 41.87 47.38 0.49 

Naphthalene A3-v1 2.31E-03 4.04E-04 6.18E-03 3.45E-04 1 145.12 164.21 1.00 

Phenanthrene A3-v0 2.06E-04 1.06E-04 4.30E-04 8.36E-05 1 93.74 106.07 1.00 

Phenol A3-v0 1.72E-03 1.82E-03 2.08E-03 1.26E-03 1 24.34 27.54 1.00 

Propylene A3-v0 1.20E-02 1.13E-02 1.38E-02 1.10E-02 1 13.02 14.73 0.00 

Pyrene A3-v0 1.25E-05 7.14E-06 2.62E-05 4.04E-06 1 96.40 109.08 1.00 

Toluene A3-v0 2.63E-02 2.46E-02 3.03E-02 2.41E-02 1 13.02 14.73 0.00 

Xylene (Total) A3-v0 3.03E-02 2.84E-02 3.49E-02 2.77E-02 1 13.02 14.73 0.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-23 

Table D-8b. Summary of Data for Emission Factor Development – 

Heaters Firing Natural Gas and Refinery Fuel Gas 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty,

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A3-v0 4.05E-09 1.38E-09 9.73E-09 1.05E-09 1 121.25 137.21 1.00 

Acenaphthylene A3-v1 3.16E-08 1.31E-09 9.23E-08 1.08E-09 1 166.64 188.56 1.00 

Acetaldehyde C3-v0 7.02E-06 6.94E-06 7.52E-06 6.59E-06 1 6.67 7.55 1.00 

Acrolein C3-v0 1.08E-06 1.10E-06 1.12E-06 1.03E-06 1 4.51 5.11 0.00 

Anthracene A3-v0 5.59E-09 4.60E-09 7.69E-09 4.48E-09 1 32.56 36.85 1.00 

Benzene A3-v0 1.01E-05 1.02E-05 1.06E-05 9.61E-06 1 4.81 5.44 0.00 

Benzo(a)anthracene A3-v0 5.18E-09 4.34E-09 8.97E-09 2.23E-09 1 66.60 75.36 1.00 

Benzo(a)pyrene A3-v1 3.24E-09 3.78E-09 5.65E-09 2.82E-10 1 84.14 95.21 0.97 

Benzo(b)fluoranthene A3-v0 1.44E-09 1.03E-09 2.38E-09 9.21E-10 1 56.34 63.75 1.00 

Benzo(g,h,i)perylene A3-v0 2.22E-10 8.16E-11 5.13E-10 7.08E-11 1 113.71 128.67 0.77 

Benzo(k)fluoranthene A3-v0 7.64E-10 4.49E-10 1.63E-09 2.10E-10 1 99.78 112.91 0.92 

Chrysene A3-v0 4.27E-10 3.62E-10 6.67E-10 2.52E-10 1 50.33 56.95 0.52 

Dibenz(a,h)anthracene A3-v0 7.45E-11 5.73E-11 1.12E-10 5.48E-11 1 43.05 48.72 0.00 

Fluoranthene A3-v0 9.73E-09 5.86E-09 2.05E-08 2.82E-09 1 97.23 110.02 1.00 

Fluorene A3-v1 3.49E-07 8.52E-08 9.09E-07 5.20E-08 1 139.21 157.53 1.00 

Formaldehyde C3-v0 2.19E-05 9.37E-06 4.74E-05 9.10E-06 1 100.34 113.54 1.00 

Indeno(1,2,3-

cd)pyrene A3-v0 2.45E-10 2.08E-10 3.58E-10 1.68E-10 1 41.08 46.49 0.49 

Naphthalene A3-v1 1.24E-06 2.08E-07 3.32E-06 1.96E-07 1 145.06 164.15 1.00 

Phenanthrene A3-v0 1.11E-07 6.02E-08 2.31E-07 4.29E-08 1 93.26 105.53 1.00 

Phenol A3-v0 9.22E-07 9.35E-07 1.12E-06 7.14E-07 1 21.82 24.69 1.00 

Propylene A3-v0 5.75E-06 5.78E-06 6.01E-06 5.46E-06 1 4.81 5.44 0.00 

Pyrene A3-v0 6.74E-09 4.05E-09 1.41E-08 2.08E-09 1 95.66 108.24 1.00 

Toluene A3-v0 1.26E-05 1.26E-05 1.31E-05 1.19E-05 1 4.81 5.44 0.00 

Xylene (Total) A3-v0 1.45E-05 1.46E-05 1.51E-05 1.38E-05 1 4.81 5.44 0.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-24 

Table D-9a. Summary of Data for Emission Factor Development – Heaters Firing Fuel Oil 

Substance 

CARB 

Rating 

Emission Factor (lb/Mgal) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene C3-v1 1.75E-06 2.20E-06 2.99E-06 6.81E-08 1 86.27 97.62 1.00 

Acenaphthylene C3-v0 8.02E-08 5.33E-08 1.37E-07 5.03E-08 1 61.23 69.29 1.00 

Acetaldehyde C3-v0 5.43E-04 5.44E-04 5.48E-04 5.38E-04 1 0.98 1.11 0.00 

Acrolein C3-v0 5.98E-04 5.99E-04 6.03E-04 5.91E-04 1 0.95 1.07 0.00 

Anthracene C3-v0 6.62E-08 6.81E-08 7.41E-08 5.65E-08 1 13.48 15.25 1.00 

Arsenic D3-v0 8.34E-04 8.28E-04 8.62E-04 8.13E-04 1 3.01 3.41 0.00 

Benzene A3-v0 8.47E-03 8.49E-03 8.74E-03 8.19E-03 1 3.22 3.65 0.00 

Benzo(a)anthracene C3-v1 3.84E-06 2.05E-07 1.12E-05 1.33E-07 1 165.56 187.35 1.00 

Benzo(a)pyrene C3-v0 9.80E-08 8.63E-08 1.84E-07 2.40E-08 1 82.16 92.97 1.00 

Benzo(b)fluoranthene C3-v0 7.95E-07 6.37E-07 1.15E-06 5.98E-07 1 38.74 43.84 1.00 

Benzo(e)pyrene C3-v0 5.54E-07 5.30E-07 7.73E-07 3.60E-07 1 37.44 42.36 1.00 

Benzo(g,h,i)perylene C3-v1 2.12E-06 5.50E-07 5.57E-06 2.55E-07 1 140.55 159.04 1.00 

Benzo(k)fluoranthene C3-v0 3.36E-08 2.08E-08 6.81E-08 1.18E-08 1 90.02 101.86 1.00 

Beryllium D3-v0 7.78E-05 7.64E-05 8.66E-05 7.04E-05 1 10.51 11.89 0.00 

1,3-Butadiene A3-v0 1.95E-02 1.96E-02 2.01E-02 1.89E-02 1 3.14 3.55 0.00 

Chloroform A3-v0 8.63E-03 8.65E-03 8.88E-03 8.35E-03 1 3.06 3.46 0.00 

2-Chloronaphthalene C3-v2 1.17E-05 5.33E-08 3.50E-05 3.57E-08 1 172.55 195.25 1.00 

Chromium (Total) A3-v0 2.54E-03 2.66E-03 2.74E-03 2.22E-03 1 11.14 12.60 1.00 

Chrysene C3-v1 1.12E-05 2.80E-06 2.92E-05 1.54E-06 1 139.73 158.12 1.00 

Copper D3-v0 2.62E-03 1.64E-03 4.58E-03 1.63E-03 1 64.94 73.48 1.00 

Dibenz(a,h)anthracene C3-v1 1.76E-06 1.18E-07 5.09E-06 6.54E-08 1 164.18 185.78 1.00 

Dioxin:4D 2378 C3-v0 4.96E-10 5.94E-10 5.97E-10 2.97E-10 1 34.70 39.26 0.00 

Dioxin:5D 12378 C3-v1 2.49E-09 5.94E-10 6.57E-09 2.97E-10 1 142.30 161.02 0.00 

Dioxin:6D 123478 C3-v1 2.19E-09 5.94E-10 5.68E-09 2.97E-10 1 138.10 156.28 0.00 

Dioxin:6D 123678 C3-v1 2.99E-09 5.94E-10 8.07E-09 2.97E-10 1 147.43 166.83 0.07 

Dioxin:6D 123789 C3-v1 4.78E-09 5.94E-10 1.34E-08 2.97E-10 1 157.08 177.75 0.04 

Dioxin:7D 1234678 C3-v1 1.33E-08 4.45E-09 3.29E-08 2.68E-09 1 127.05 143.76 1.00 

Dioxin:8D C3-v0 4.68E-08 5.64E-08 5.97E-08 2.41E-08 1 42.12 47.67 1.00 

Fluoranthene C3-v0 1.97E-06 2.28E-06 2.48E-06 1.13E-06 1 37.09 41.97 1.00 

Fluorene C3-v0 7.48E-05 3.25E-05 1.67E-04 2.52E-05 1 106.53 120.55 1.00 

Formaldehyde C3-v0 3.80E-03 3.81E-03 3.84E-03 3.77E-03 1 0.95 1.08 0.00 

Furan:4F 2378 C3-v2 8.93E-08 1.48E-09 2.66E-07 5.95E-10 1 171.19 193.71 1.00 

Furan:5F 12378 C3-v1 8.56E-09 5.94E-10 2.48E-08 2.97E-10 1 164.20 185.80 0.00 

Furan:5F 23478 C3-v2 1.52E-08 5.94E-10 4.48E-08 2.97E-10 1 168.14 190.26 0.00 

Furan:6F 123478 C3-v2 1.92E-08 5.94E-10 5.68E-08 1.49E-10 1 169.85 192.20 0.01 

Furan:6F 123678 C3-v2 6.12E-09 2.97E-10 1.79E-08 1.49E-10 1 166.91 188.87 0.02 

Furan:5F 23478 C3-v2 1.52E-08 5.94E-10 4.48E-08 2.97E-10 1 168.14 190.26 0.00 

Furan:6F 123478 C3-v2 1.92E-08 5.94E-10 5.68E-08 1.49E-10 1 169.85 192.20 0.01 

(continued) 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-25 

Table D-9a. Summary of Data for Emission Factor Development – Heaters Firing Fuel Oil 

(continued) 

Substance 

CARB 

Rating 

Emission Factor (lb/Mgal) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Furan:6F 123678 C3-v2 6.12E-09 2.97E-10 1.79E-08 1.49E-10 1 166.91 188.87 0.02 

Furan:6F 123789 C3-v0 4.96E-10 5.94E-10 5.97E-10 2.97E-10 1 34.70 39.26 0.00 

Furan:6F 234678 C3-v1 8.76E-09 8.91E-10 2.48E-08 5.95E-10 1 158.52 179.38 0.03 

Furan:7F 1234678 C3-v1 1.95E-08 1.19E-09 5.68E-08 5.95E-10 1 165.30 187.05 1.00 

Furan:7F 1234789 C3-v0 1.19E-09 5.94E-10 2.69E-09 2.97E-10 1 109.22 123.59 0.00 

Furan:8F C3-v1 1.04E-08 4.75E-09 2.54E-08 1.19E-09 1 125.10 141.57 1.00 

Indeno(1,2,3-cd)pyrene C3-v1 1.81E-06 1.55E-07 5.12E-06 1.48E-07 1 158.71 179.59 1.00 

Lead D3-v0 2.96E-04 1.79E-04 5.48E-04 1.62E-04 1 73.61 83.30 0.62 

Manganese D3-v0 1.89E-03 1.79E-03 2.22E-03 1.67E-03 1 15.12 17.11 0.39 

Mercury D3-v0 1.72E-05 1.29E-05 2.83E-05 1.04E-05 1 56.41 63.84 0.00 

2-Methylnaphthalene C3-v1 3.60E-05 1.06E-05 9.29E-05 4.54E-06 1 137.05 155.09 1.00 

Naphthalene C3-v0 8.46E-04 1.04E-03 1.11E-03 3.88E-04 1 47.07 53.26 1.00 

Nickel D3-v0 3.46E-01 3.47E-01 4.09E-01 2.81E-01 1 18.57 21.01 1.00 

Perylene C3-v0 7.41E-08 3.57E-08 1.66E-07 2.07E-08 1 107.75 121.93 1.00 

Phenanthrene C3-v1 2.49E-05 1.18E-05 6.02E-05 2.83E-06 1 123.75 140.04 1.00 

Propylene A3-v0 1.52E-02 1.52E-02 1.56E-02 1.47E-02 1 3.01 3.41 0.00 

Pyrene C3-v0 1.32E-06 1.19E-06 2.14E-06 6.28E-07 1 57.94 65.56 1.00 

Selenium D3-v0 4.63E-03 3.96E-03 6.59E-03 3.33E-03 1 37.32 42.23 0.00 

Toluene A3-v0 9.99E-03 1.00E-02 1.03E-02 9.67E-03 1 3.06 3.46 0.00 

Xylene (Total) A3-v0 1.92E-02 1.92E-02 1.98E-02 1.86E-02 1 3.21 3.63 0.00 

Zinc D3-v0 8.93E-03 8.35E-03 1.22E-02 6.27E-03 1 33.43 37.83 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-26 

Table D-9b. Summary of Data for Emission Factor Development – Heaters Firing Fuel Oil 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene C3-v1 1.22E-08 1.53E-08 2.09E-08 4.76E-10 1 86.27 97.62 1.00 

Acenaphthylene C3-v0 5.59E-10 3.72E-10 9.55E-10 3.51E-10 1 61.23 69.29 1.00 

Acetaldehyde C3-v0 3.79E-06 3.80E-06 3.83E-06 3.75E-06 1 0.98 1.11 0.00 

Acrolein C3-v0 4.17E-06 4.18E-06 4.21E-06 4.13E-06 1 0.95 1.07 0.00 

Anthracene C3-v0 4.62E-10 4.75E-10 5.17E-10 3.94E-10 1 13.48 15.25 1.00 

Arsenic D3-v0 5.82E-06 5.78E-06 6.02E-06 5.67E-06 1 3.01 3.41 0.00 

Benzene A3-v0 5.91E-05 5.92E-05 6.10E-05 5.72E-05 1 3.22 3.65 0.00 

Benzo(a)anthracene C3-v1 2.68E-08 1.43E-09 7.79E-08 9.30E-10 1 165.56 187.35 1.00 

Benzo(a)pyrene C3-v0 6.84E-10 6.02E-10 1.28E-09 1.67E-10 1 82.16 92.97 1.00 

Benzo(b)fluoranthene C3-v0 5.55E-09 4.44E-09 8.02E-09 4.17E-09 1 38.74 43.84 1.00 

Benzo(e)pyrene C3-v0 3.87E-09 3.70E-09 5.39E-09 2.51E-09 1 37.44 42.36 1.00 

Benzo(g,h,i)perylene C3-v1 1.48E-08 3.84E-09 3.88E-08 1.78E-09 1 140.55 159.04 1.00 

Benzo(k)fluoranthene C3-v0 2.35E-10 1.45E-10 4.76E-10 8.27E-11 1 90.02 101.86 1.00 

Beryllium D3-v0 5.43E-07 5.33E-07 6.04E-07 4.92E-07 1 10.51 11.89 0.00 

1,3-Butadiene A3-v0 1.36E-04 1.37E-04 1.40E-04 1.32E-04 1 3.14 3.55 0.00 

Cadmium D3-v1 5.73E-06 8.28E-06 8.60E-06 2.99E-07 1 82.13 92.94 1.00 

Chloroform A3-v0 6.02E-05 6.03E-05 6.20E-05 5.83E-05 1 3.06 3.46 0.00 

2-Chloronaphthalene C3-v2 8.16E-08 3.72E-10 2.44E-07 2.49E-10 1 172.55 195.25 1.00 

Chromium (Hex) A3-v0 2.00E-06 2.14E-06 2.18E-06 1.67E-06 1 14.20 16.07 0.00 

Chromium (Total) A3-v0 1.77E-05 1.85E-05 1.91E-05 1.55E-05 1 11.14 12.60 1.00 

Chrysene C3-v1 7.81E-08 1.95E-08 2.04E-07 1.07E-08 1 139.73 158.12 1.00 

Copper D3-v0 1.83E-05 1.15E-05 3.20E-05 1.14E-05 1 64.94 73.48 1.00 

Dibenz(a,h)anthracene C3-v1 1.23E-08 8.23E-10 3.55E-08 4.57E-10 1 164.18 185.78 1.00 

Dioxin:4D 2378 C3-v0 3.46E-12 4.15E-12 4.17E-12 2.08E-12 1 34.70 39.26 0.00 

Dioxin:5D 12378 C3-v1 1.74E-11 4.15E-12 4.59E-11 2.08E-12 1 142.30 161.02 0.00 

Dioxin:6D 123478 C3-v1 1.53E-11 4.15E-12 3.96E-11 2.08E-12 1 138.10 156.28 0.00 

Dioxin:6D 123678 C3-v1 2.08E-11 4.15E-12 5.63E-11 2.08E-12 1 147.43 166.83 0.07 

Dioxin:6D 123789 C3-v1 3.33E-11 4.15E-12 9.38E-11 2.08E-12 1 157.08 177.75 0.04 

Dioxin:7D 1234678 C3-v1 9.30E-11 3.11E-11 2.29E-10 1.87E-11 1 127.05 143.76 1.00 

Dioxin:8D C3-v0 3.26E-10 3.94E-10 4.17E-10 1.68E-10 1 42.12 47.67 1.00 

Fluoranthene C3-v0 1.37E-08 1.59E-08 1.73E-08 7.89E-09 1 37.09 41.97 1.00 

Fluorene C3-v0 5.22E-07 2.26E-07 1.16E-06 1.76E-07 1 106.53 120.55 1.00 

Formaldehyde C3-v0 2.65E-05 2.66E-05 2.68E-05 2.63E-05 1 0.95 1.08 0.00 

Furan:4F 2378 C3-v2 6.23E-10 1.04E-11 1.86E-09 4.15E-12 1 171.19 193.71 1.00 

Furan:5F 12378 C3-v1 5.97E-11 4.15E-12 1.73E-10 2.08E-12 1 164.20 185.80 0.00 

Furan:5F 23478 C3-v2 1.06E-10 4.15E-12 3.13E-10 2.08E-12 1 168.14 190.26 0.00 

Furan:6F 123478 C3-v2 1.34E-10 4.15E-12 3.96E-10 1.04E-12 1 169.85 192.20 0.01 

Furan:6F 123678 C3-v2 4.27E-11 2.07E-12 1.25E-10 1.04E-12 1 166.91 188.87 0.02 

(continued) 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-27 

Table D-9b. Summary of Data for Emission Factor Development – Heaters Firing Fuel Oil 

(continued) 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Furan:6F 123789 C3-v0 3.46E-12 4.15E-12 4.17E-12 2.08E-12 1 34.70 39.26 0.00 

Furan:6F 234678 C3-v1 6.11E-11 6.22E-12 1.73E-10 4.15E-12 1 158.52 179.38 0.03 

Furan:7F 1234678 C3-v1 1.36E-10 8.29E-12 3.96E-10 4.15E-12 1 165.30 187.05 1.00 

Furan:7F 1234789 C3-v0 8.33E-12 4.15E-12 1.88E-11 2.08E-12 1 109.22 123.59 0.00 

Furan:8F C3-v1 7.29E-11 3.32E-11 1.77E-10 8.30E-12 1 125.10 141.57 1.00 

Indeno(1,2,3-cd)pyrene C3-v1 1.26E-08 1.08E-09 3.58E-08 1.03E-09 1 158.71 179.59 1.00 

Lead D3-v0 2.07E-06 1.25E-06 3.83E-06 1.13E-06 1 73.61 83.30 0.62 

Manganese D3-v0 1.32E-05 1.25E-05 1.55E-05 1.17E-05 1 15.12 17.11 0.39 

Mercury D3-v0 1.20E-07 8.99E-08 1.98E-07 7.28E-08 1 56.41 63.84 0.00 

2-Methylnaphthalene C3-v1 2.51E-07 7.40E-08 6.49E-07 3.17E-08 1 137.05 155.09 1.00 

Naphthalene C3-v0 5.91E-06 7.28E-06 7.73E-06 2.71E-06 1 47.07 53.26 1.00 

Nickel D3-v0 2.41E-03 2.42E-03 2.86E-03 1.96E-03 1 18.57 21.01 1.00 

Perylene C3-v0 5.17E-10 2.49E-10 1.16E-09 1.45E-10 1 107.75 121.93 1.00 

Phenanthrene C3-v1 1.74E-07 8.23E-08 4.20E-07 1.98E-08 1 123.75 140.04 1.00 

Propylene A3-v0 1.06E-04 1.06E-04 1.09E-04 1.03E-04 1 3.01 3.41 0.00 

Pyrene C3-v0 9.22E-09 8.32E-09 1.49E-08 4.38E-09 1 57.94 65.56 1.00 

Selenium D3-v0 3.23E-05 2.77E-05 4.60E-05 2.33E-05 1 37.32 42.23 0.00 

Toluene A3-v0 6.97E-05 6.99E-05 7.18E-05 6.75E-05 1 3.06 3.46 0.00 

Xylene (Total) A3-v0 1.34E-04 1.34E-04 1.38E-04 1.29E-04 1 3.21 3.63 0.00 

Zinc D3-v0 6.23E-05 5.83E-05 8.49E-05 4.38E-05 1 33.43 37.83 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-28 

Table D-10a. Summary of Data for Emission Factor Development – Heaters Firing Refinery 

Fuel Gas Controlled with Selective Non-Catalytic Reduction (NOx) 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A2-v0 2.33E-06 1.46E-06 5.28E-06 1.11E-06 4 65.80 38.88 0.95 

Acenaphthylene A2-v0 1.52E-06 1.39E-06 2.64E-06 9.83E-07 4 38.62 22.82 0.51 

Acetaldehyde B1-v3 1.95E-02 1.08E-02 1.12E-01 1.10E-04 8 129.02 51.62 0.88 

Anthracene A2-v0 2.81E-06 2.40E-06 5.93E-06 1.01E-06 4 57.37 33.90 0.92 

Antimony C3-v0 5.81E-04 6.56E-04 8.51E-04 2.36E-04 1 54.13 61.25 1.00 

Arsenic C3-v0 9.54E-04 1.11E-03 1.43E-03 3.19E-04 1 60.10 68.00 1.00 

Barium C3-v0 6.49E-03 6.49E-03 6.64E-03 6.33E-03 1 2.45 2.78 0.00 

Benzene B1-v2 8.42E-02 6.76E-02 2.76E-01 2.35E-03 11 93.71 31.97 0.02 

Benzo(a)anthracene A1-v2 3.70E-05 7.11E-06 3.97E-04 1.00E-06 9 261.62 100.56 1.00 

Benzo(a)pyrene A1-v3 9.89E-05 2.20E-06 1.32E-03 9.83E-07 9 344.55 132.44 0.98 

Benzo(b)fluoranthene A1-v2 4.61E-05 4.20E-06 6.04E-04 9.83E-07 9 315.76 121.37 0.99 

Benzo(g,h,i)perylene A2-v0 1.17E-06 1.04E-06 1.41E-06 9.83E-07 4 16.09 9.51 0.00 

Benzo(k)fluoranthene A1-v2 2.72E-05 2.66E-06 3.40E-04 9.83E-07 9 309.39 118.92 0.96 

Beryllium C3-v0 2.88E-04 2.89E-04 2.95E-04 2.81E-04 1 2.45 2.78 0.00 

Cadmium C3-v0 1.11E-03 1.08E-03 1.33E-03 9.15E-04 1 18.76 21.23 1.00 

Chromium (Hex) C3-v0 2.43E-03 2.48E-03 2.51E-03 2.30E-03 1 4.62 5.23 0.00 

Chromium (Total) C3-v0 1.20E-03 7.38E-04 2.16E-03 7.03E-04 1 69.39 78.52 0.60 

Chrysene A2-v0 1.66E-06 1.29E-06 5.37E-06 9.83E-07 4 76.71 45.33 0.63 

Copper C3-v0 4.73E-03 2.16E-03 1.05E-02 1.48E-03 1 106.76 120.81 1.00 

Dibenz(a,h)anthracene A1-v2 1.06E-05 1.95E-06 1.31E-04 6.78E-07 9 262.22 100.79 0.00 

Ethylbenzene A2-v1 3.04E-02 1.74E-02 9.50E-02 2.53E-03 4 100.75 57.01 0.51 

Fluoranthene A2-v0 3.06E-06 3.03E-06 5.66E-06 1.72E-06 4 37.95 22.43 1.00 

Fluorene A2-v0 1.06E-05 8.55E-06 2.64E-05 3.33E-06 4 67.66 39.98 1.00 

Formaldehyde B1-v3 1.51E-01 3.03E-02 1.76E+00 7.92E-04 7 254.14 108.70 1.00 

Hydrogen Sulfide A1-v1 4.05E-01 3.27E-01 1.20E+00 1.82E-02 7 84.49 36.13 0.00 

Indeno(1,2,3-cd)pyrene A1-v3 1.15E-04 2.29E-06 1.55E-03 9.83E-07 9 342.12 131.50 0.99 

Lead C3-v0 5.49E-03 4.43E-03 8.43E-03 3.61E-03 1 47.03 53.22 1.00 

Manganese C3-v0 7.65E-03 7.03E-03 1.37E-02 2.21E-03 1 75.45 85.38 1.00 

Mercury C3-v0 2.02E-04 1.97E-04 2.17E-04 1.92E-04 1 6.49 7.34 0.36 

Naphthalene A2-v0 3.02E-04 2.43E-04 6.96E-04 1.33E-04 4 62.74 37.08 1.00 

Nickel C3-v1 1.06E-02 1.48E-03 2.88E-02 1.44E-03 1 149.30 168.95 0.95 

Phenanthrene A2-v0 1.44E-05 1.49E-05 2.17E-05 7.69E-06 4 32.45 19.18 1.00 

Phenol C1-v1 6.96E-03 4.70E-03 2.68E-02 2.93E-04 7 103.61 44.32 0.97 

Phosphorus C3-v0 7.21E-04 7.22E-04 7.38E-04 7.03E-04 1 2.45 2.78 0.00 

Propylene A2-v0 2.05E-03 2.14E-03 2.91E-03 1.00E-03 3 25.36 16.57 0.05 

Pyrene A2-v0 2.84E-06 2.63E-06 5.09E-06 1.78E-06 4 33.95 20.06 1.00 

Selenium C3-v0 2.20E-05 2.28E-05 2.85E-05 1.48E-05 1 31.23 35.34 0.78 

(continued) 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-29 

Table D-10a. Summary of Data for Emission Factor Development – Heaters Firing Refinery 

Fuel Gas Controlled with Selective Non-Catalytic Reduction (NOx) (continued) 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Silver C3-v1 1.81E-03 1.48E-03 3.61E-03 3.53E-04 1 91.23 103.24 0.94 

Thallium C3-v0 6.49E-03 6.49E-03 6.64E-03 6.33E-03 1 2.45 2.78 0.00 

Toluene D1-v2 1.37E-01 7.81E-02 1.21E+00 3.71E-03 11 154.31 52.65 0.55 

Xylene (Total) A2-v1 3.74E-02 3.37E-02 9.90E-02 4.27E-03 4 95.86 54.24 0.60 

Zinc C3-v0 2.34E-02 2.89E-02 3.18E-02 9.52E-03 1 51.72 58.53 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-30 

Table D-10b. Summary of Data for Emission Factor Development – Heaters Firing Refinery 

Fuel Gas Controlled with Selective Non-Catalytic Reduction (NOx) 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A2-v0 2.36E-09 1.55E-09 5.61E-09 1.20E-09 4 69.14 40.86 0.95 

Acenaphthylene A2-v0 1.55E-09 1.25E-09 2.74E-09 1.02E-09 4 41.70 24.64 0.51 

Acetaldehyde B1-v3 1.53E-05 8.12E-06 8.55E-05 8.41E-08 8 126.30 50.53 0.88 

Anthracene A2-v0 2.87E-09 2.30E-09 6.45E-09 1.09E-09 4 61.24 36.19 0.92 

Antimony C3-v0 5.17E-07 5.84E-07 7.58E-07 2.10E-07 1 54.13 61.25 1.00 

Arsenic C3-v0 8.50E-07 9.90E-07 1.28E-06 2.84E-07 1 60.10 68.00 1.00 

Barium C3-v0 5.78E-06 5.78E-06 5.92E-06 5.63E-06 1 2.45 2.78 0.00 

Benzene B1-v1 6.47E-05 5.49E-05 1.85E-04 2.54E-06 11 87.67 29.91 0.02 

Benzo(a)anthracene A1-v2 3.21E-08 5.40E-09 3.39E-07 1.05E-09 9 265.30 101.97 1.00 

Benzo(a)pyrene A1-v3 8.96E-08 1.73E-09 1.38E-06 1.02E-09 9 352.36 135.44 0.98 

Benzo(b)fluoranthene A1-v2 4.04E-08 3.31E-09 4.87E-07 1.02E-09 9 314.58 120.92 0.99 

Benzo(g,h,i)perylene A2-v0 1.17E-09 1.10E-09 1.40E-09 1.02E-09 4 11.55 6.82 0.00 

Benzo(k)fluoranthene A1-v2 2.41E-08 2.18E-09 2.96E-07 1.02E-09 9 310.01 119.16 0.96 

Beryllium C3-v0 2.57E-07 2.57E-07 2.63E-07 2.50E-07 1 2.45 2.78 0.00 

Cadmium C3-v0 9.88E-07 9.65E-07 1.18E-06 8.15E-07 1 18.76 21.23 1.00 

Chromium (Hex) C3-v0 2.17E-06 2.21E-06 2.24E-06 2.05E-06 1 4.62 5.23 0.00 

Chromium (Total) C3-v0 1.07E-06 6.57E-07 1.93E-06 6.26E-07 1 69.39 78.52 0.60 

Chrysene A2-v0 1.63E-09 1.23E-09 4.79E-09 1.02E-09 4 66.84 39.50 0.63 

Copper C3-v0 4.21E-06 1.93E-06 9.39E-06 1.31E-06 1 106.76 120.81 1.00 

Dibenz(a,h)anthracene A1-v2 1.02E-08 1.60E-09 1.37E-07 5.93E-10 9 279.09 107.28 0.00 

Ethylbenzene A2-v1 3.02E-05 1.79E-05 1.03E-04 2.72E-06 4 104.65 59.21 0.51 

Fluoranthene A2-v0 3.06E-09 3.14E-09 5.04E-09 1.85E-09 4 33.80 19.97 1.00 

Fluorene A2-v0 1.08E-08 8.77E-09 2.74E-08 2.96E-09 4 70.62 41.74 1.00 

Formaldehyde B1-v3 1.11E-04 1.90E-05 1.34E-03 7.67E-07 7 262.94 112.46 1.00 

Hydrogen Sulfide A1-v1 2.92E-04 2.46E-04 8.04E-04 1.76E-05 7 75.53 32.30 0.00 

Indeno(1,2,3-cd)pyrene A1-v3 1.03E-07 1.75E-09 1.42E-06 1.02E-09 9 343.01 131.85 0.99 

Lead C3-v0 4.89E-06 3.94E-06 7.51E-06 3.21E-06 1 47.03 53.22 1.00 

Manganese C3-v0 6.81E-06 6.26E-06 1.22E-05 1.97E-06 1 75.45 85.38 1.00 

Mercury C3-v0 1.80E-07 1.75E-07 1.93E-07 1.71E-07 1 6.49 7.34 0.36 

Naphthalene A2-v0 3.13E-07 2.61E-07 7.58E-07 1.19E-07 4 66.90 39.53 1.00 

Nickel C3-v1 9.42E-06 1.31E-06 2.57E-05 1.29E-06 1 149.30 168.95 0.95 

Phenanthrene A2-v0 1.46E-08 1.50E-08 2.25E-08 6.91E-09 4 32.60 19.27 1.00 

Phenol C1-v1 5.63E-06 3.14E-06 2.54E-05 2.84E-07 7 114.62 49.02 0.97 

Phosphorus C3-v0 6.42E-07 6.43E-07 6.57E-07 6.26E-07 1 2.45 2.78 0.00 

Propylene A2-v0 2.17E-06 2.22E-06 2.98E-06 1.08E-06 3 23.69 15.47 0.05 

Pyrene A2-v0 2.84E-09 2.72E-09 4.53E-09 1.87E-09 4 28.87 17.06 1.00 

Selenium C3-v0 1.96E-08 2.03E-08 2.54E-08 1.32E-08 1 31.23 35.34 0.78 

(continued) 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-31 

Table D-10b. Summary of Data for Emission Factor Development – Heaters Firing Refinery 

Fuel Gas Controlled with Selective Non-Catalytic Reduction (NOx) (continued) 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Silver C3-v1 1.61E-06 1.31E-06 3.21E-06 3.14E-07 1 91.23 103.24 0.94 

Thallium C3-v0 5.78E-06 5.78E-06 5.92E-06 5.63E-06 1 2.45 2.78 0.00 

Toluene D1-v2 1.07E-04 7.00E-05 9.19E-04 4.04E-06 11 148.57 50.69 0.55 

Xylene (Total) A2-v1 3.73E-05 3.16E-05 1.08E-04 4.66E-06 4 99.32 56.19 0.60 

Zinc C3-v0 2.08E-05 2.58E-05 2.83E-05 8.48E-06 1 51.72 58.53 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-32 

Table D-11a. Summary of Data for Emission Factor Development – 

Heaters Firing Refinery Fuel Gas 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A2-v0 2.33E-06 1.46E-06 5.28E-06 1.11E-06 4 65.80 38.88 0.95 

Acenaphthylene A2-v0 1.52E-06 1.39E-06 2.64E-06 9.83E-07 4 38.62 22.82 0.51 

Acetaldehyde B1-v3 1.95E-02 1.08E-02 1.12E-01 1.10E-04 8 129.02 51.62 0.88 

Anthracene A2-v0 2.81E-06 2.40E-06 5.93E-06 1.01E-06 4 57.37 33.90 0.92 

Antimony C3-v0 5.81E-04 6.56E-04 8.51E-04 2.36E-04 1 54.13 61.25 1.00 

Arsenic C3-v0 9.54E-04 1.11E-03 1.43E-03 3.19E-04 1 60.10 68.00 1.00 

Barium C3-v0 6.49E-03 6.49E-03 6.64E-03 6.33E-03 1 2.45 2.78 0.00 

Benzene B1-v2 8.42E-02 6.76E-02 2.76E-01 2.35E-03 11 93.71 31.97 0.02 

Benzo(a)anthracene A1-v2 3.70E-05 7.11E-06 3.97E-04 1.00E-06 9 261.62 100.56 1.00 

Benzo(a)pyrene A1-v3 9.89E-05 2.20E-06 1.32E-03 9.83E-07 9 344.55 132.44 0.98 

Benzo(b)fluoranthene A1-v2 4.61E-05 4.20E-06 6.04E-04 9.83E-07 9 315.76 121.37 0.99 

Benzo(g,h,i)perylene A2-v0 1.17E-06 1.04E-06 1.41E-06 9.83E-07 4 16.09 9.51 0.00 

Benzo(k)fluoranthene A1-v2 2.72E-05 2.66E-06 3.40E-04 9.83E-07 9 309.39 118.92 0.96 

Beryllium C3-v0 2.88E-04 2.89E-04 2.95E-04 2.81E-04 1 2.45 2.78 0.00 

Cadmium C3-v0 1.11E-03 1.08E-03 1.33E-03 9.15E-04 1 18.76 21.23 1.00 

Chromium (Hex) C3-v0 2.43E-03 2.48E-03 2.51E-03 2.30E-03 1 4.62 5.23 0.00 

Chromium (Total) C3-v0 1.20E-03 7.38E-04 2.16E-03 7.03E-04 1 69.39 78.52 0.60 

Chrysene A2-v0 1.66E-06 1.29E-06 5.37E-06 9.83E-07 4 76.71 45.33 0.63 

Copper C3-v0 4.73E-03 2.16E-03 1.05E-02 1.48E-03 1 106.76 120.81 1.00 

Dibenz(a,h)anthracene A1-v2 1.06E-05 1.95E-06 1.31E-04 6.78E-07 9 262.22 100.79 0.00 

Ethylbenzene A2-v1 3.04E-02 1.74E-02 9.50E-02 2.53E-03 4 100.75 57.01 0.51 

Fluoranthene A2-v0 3.06E-06 3.03E-06 5.66E-06 1.72E-06 4 37.95 22.43 1.00 

Fluorene A2-v0 1.06E-05 8.55E-06 2.64E-05 3.33E-06 4 67.66 39.98 1.00 

Formaldehyde B1-v3 1.51E-01 3.03E-02 1.76E+00 7.92E-04 7 254.14 108.70 1.00 

Hydrogen Sulfide A1-v1 4.05E-01 3.27E-01 1.20E+00 1.82E-02 7 84.49 36.13 0.00 

Indeno(1,2,3-cd)pyrene A1-v3 1.15E-04 2.29E-06 1.55E-03 9.83E-07 9 342.12 131.50 0.99 

Lead C3-v0 5.49E-03 4.43E-03 8.43E-03 3.61E-03 1 47.03 53.22 1.00 

Manganese C3-v0 7.65E-03 7.03E-03 1.37E-02 2.21E-03 1 75.45 85.38 1.00 

Mercury C3-v0 2.02E-04 1.97E-04 2.17E-04 1.92E-04 1 6.49 7.34 0.36 

Naphthalene A2-v0 3.02E-04 2.43E-04 6.96E-04 1.33E-04 4 62.74 37.08 1.00 

Nickel C3-v1 1.06E-02 1.48E-03 2.88E-02 1.44E-03 1 149.30 168.95 0.95 

Phenanthrene A2-v0 1.44E-05 1.49E-05 2.17E-05 7.69E-06 4 32.45 19.18 1.00 

Phenol C1-v1 6.96E-03 4.70E-03 2.68E-02 2.93E-04 7 103.61 44.32 0.97 

Phosphorus C3-v0 7.21E-04 7.22E-04 7.38E-04 7.03E-04 1 2.45 2.78 0.00 

Propylene A2-v0 2.05E-03 2.14E-03 2.91E-03 1.00E-03 3 25.36 16.57 0.05 

Pyrene A2-v0 2.84E-06 2.63E-06 5.09E-06 1.78E-06 4 33.95 20.06 1.00 

Selenium C3-v0 2.20E-05 2.28E-05 2.85E-05 1.48E-05 1 31.23 35.34 0.78 

(continued) 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-33 

Table D-11a. Summary of Data for Emission Factor Development – 

Heaters Firing Refinery Fuel Gas (continued) 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Silver C3-v1 1.81E-03 1.48E-03 3.61E-03 3.53E-04 1 91.23 103.24 0.94 

Thallium C3-v0 6.49E-03 6.49E-03 6.64E-03 6.33E-03 1 2.45 2.78 0.00 

Toluene D1-v2 1.37E-01 7.81E-02 1.21E+00 3.71E-03 11 154.31 52.65 0.55 

Xylene (Total) A2-v1 3.74E-02 3.37E-02 9.90E-02 4.27E-03 4 95.86 54.24 0.60 

Zinc C3-v0 2.34E-02 2.89E-02 3.18E-02 9.52E-03 1 51.72 58.53 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-34 

Table D-11b. Summary of Data for Emission Factor Development – 

Heaters Firing Refinery Fuel Gas 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A2-v0 2.36E-09 1.55E-09 5.61E-09 1.20E-09 4 69.14 40.86 0.95 

Acenaphthylene A2-v0 1.55E-09 1.25E-09 2.74E-09 1.02E-09 4 41.70 24.64 0.51 

Acetaldehyde B1-v3 1.53E-05 8.12E-06 8.55E-05 8.41E-08 8 126.30 50.53 0.88 

Anthracene A2-v0 2.87E-09 2.30E-09 6.45E-09 1.09E-09 4 61.24 36.19 0.92 

Antimony C3-v0 5.17E-07 5.84E-07 7.58E-07 2.10E-07 1 54.13 61.25 1.00 

Arsenic C3-v0 8.50E-07 9.90E-07 1.28E-06 2.84E-07 1 60.10 68.00 1.00 

Barium C3-v0 5.78E-06 5.78E-06 5.92E-06 5.63E-06 1 2.45 2.78 0.00 

Benzene B1-v1 6.47E-05 5.49E-05 1.85E-04 2.54E-06 11 87.67 29.91 0.02 

Benzo(a)anthracene A1-v2 3.21E-08 5.40E-09 3.39E-07 1.05E-09 9 265.30 101.97 1.00 

Benzo(a)pyrene A1-v3 8.96E-08 1.73E-09 1.38E-06 1.02E-09 9 352.36 135.44 0.98 

Benzo(b)fluoranthene A1-v2 4.04E-08 3.31E-09 4.87E-07 1.02E-09 9 314.58 120.92 0.99 

Benzo(g,h,i)perylene A2-v0 1.17E-09 1.10E-09 1.40E-09 1.02E-09 4 11.55 6.82 0.00 

Benzo(k)fluoranthene A1-v2 2.41E-08 2.18E-09 2.96E-07 1.02E-09 9 310.01 119.16 0.96 

Beryllium C3-v0 2.57E-07 2.57E-07 2.63E-07 2.50E-07 1 2.45 2.78 0.00 

Cadmium C3-v0 9.88E-07 9.65E-07 1.18E-06 8.15E-07 1 18.76 21.23 1.00 

Chromium (Hex) C3-v0 2.17E-06 2.21E-06 2.24E-06 2.05E-06 1 4.62 5.23 0.00 

Chromium (Total) C3-v0 1.07E-06 6.57E-07 1.93E-06 6.26E-07 1 69.39 78.52 0.60 

Chrysene A2-v0 1.63E-09 1.23E-09 4.79E-09 1.02E-09 4 66.84 39.50 0.63 

Copper C3-v0 4.21E-06 1.93E-06 9.39E-06 1.31E-06 1 106.76 120.81 1.00 

Dibenz(a,h)anthracene A1-v2 1.02E-08 1.60E-09 1.37E-07 5.93E-10 9 279.09 107.28 0.00 

Ethylbenzene A2-v1 3.02E-05 1.79E-05 1.03E-04 2.72E-06 4 104.65 59.21 0.51 

Fluoranthene A2-v0 3.06E-09 3.14E-09 5.04E-09 1.85E-09 4 33.80 19.97 1.00 

Fluorene A2-v0 1.08E-08 8.77E-09 2.74E-08 2.96E-09 4 70.62 41.74 1.00 

Formaldehyde B1-v3 1.11E-04 1.90E-05 1.34E-03 7.67E-07 7 262.94 112.46 1.00 

Hydrogen Sulfide A1-v1 2.92E-04 2.46E-04 8.04E-04 1.76E-05 7 75.53 32.30 0.00 

Indeno(1,2,3-cd)pyrene A1-v3 1.03E-07 1.75E-09 1.42E-06 1.02E-09 9 343.01 131.85 0.99 

Lead C3-v0 4.89E-06 3.94E-06 7.51E-06 3.21E-06 1 47.03 53.22 1.00 

Manganese C3-v0 6.81E-06 6.26E-06 1.22E-05 1.97E-06 1 75.45 85.38 1.00 

Mercury C3-v0 1.80E-07 1.75E-07 1.93E-07 1.71E-07 1 6.49 7.34 0.36 

Naphthalene A2-v0 3.13E-07 2.61E-07 7.58E-07 1.19E-07 4 66.90 39.53 1.00 

Nickel C3-v1 9.42E-06 1.31E-06 2.57E-05 1.29E-06 1 149.30 168.95 0.95 

Phenanthrene A2-v0 1.46E-08 1.50E-08 2.25E-08 6.91E-09 4 32.60 19.27 1.00 

Phenol C1-v1 5.63E-06 3.14E-06 2.54E-05 2.84E-07 7 114.62 49.02 0.97 

Phosphorus C3-v0 6.42E-07 6.43E-07 6.57E-07 6.26E-07 1 2.45 2.78 0.00 

Propylene A2-v0 2.17E-06 2.22E-06 2.98E-06 1.08E-06 3 23.69 15.47 0.05 

Pyrene A2-v0 2.84E-09 2.72E-09 4.53E-09 1.87E-09 4 28.87 17.06 1.00 

Selenium C3-v0 1.96E-08 2.03E-08 2.54E-08 1.32E-08 1 31.23 35.34 0.78 

(continued) 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-35 

Table D-11b. Summary of Data for Emission Factor Development – 

Heaters Firing Refinery Fuel Gas (continued) 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Silver C3-v1 1.61E-06 1.31E-06 3.21E-06 3.14E-07 1 91.23 103.24 0.94 

Thallium C3-v0 5.78E-06 5.78E-06 5.92E-06 5.63E-06 1 2.45 2.78 0.00 

Toluene D1-v2 1.07E-04 7.00E-05 9.19E-04 4.04E-06 11 148.57 50.69 0.55 

Xylene (Total) A2-v1 3.73E-05 3.16E-05 1.08E-04 4.66E-06 4 99.32 56.19 0.60 

Zinc C3-v0 2.08E-05 2.58E-05 2.83E-05 8.48E-06 1 51.72 58.53 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-36 

Table D-12a. Summary of Data for Emission Factor Development – Heaters Firing Refinery 

Fuel Gas Controlled with Selective Catalytic Reduction 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A2-v0 2.33E-06 1.46E-06 5.28E-06 1.11E-06 4 65.80 38.88 0.95 

Acenaphthylene A2-v0 1.52E-06 1.39E-06 2.64E-06 9.83E-07 4 38.62 22.82 0.51 

Acetaldehyde B1-v3 1.95E-02 1.08E-02 1.12E-01 1.10E-04 8 129.02 51.62 0.88 

Anthracene A2-v0 2.81E-06 2.40E-06 5.93E-06 1.01E-06 4 57.37 33.90 0.92 

Antimony C3-v0 5.81E-04 6.56E-04 8.51E-04 2.36E-04 1 54.13 61.25 1.00 

Arsenic C3-v0 9.54E-04 1.11E-03 1.43E-03 3.19E-04 1 60.10 68.00 1.00 

Barium C3-v0 6.49E-03 6.49E-03 6.64E-03 6.33E-03 1 2.45 2.78 0.00 

Benzene B1-v2 8.42E-02 6.76E-02 2.76E-01 2.35E-03 11 93.71 31.97 0.02 

Benzo(a)anthracene A1-v2 3.70E-05 7.11E-06 3.97E-04 1.00E-06 9 261.62 100.56 1.00 

Benzo(a)pyrene A1-v3 9.89E-05 2.20E-06 1.32E-03 9.83E-07 9 344.55 132.44 0.98 

Benzo(b)fluoranthene A1-v2 4.61E-05 4.20E-06 6.04E-04 9.83E-07 9 315.76 121.37 0.99 

Benzo(g,h,i)perylene A2-v0 1.17E-06 1.04E-06 1.41E-06 9.83E-07 4 16.09 9.51 0.00 

Benzo(k)fluoranthene A1-v2 2.72E-05 2.66E-06 3.40E-04 9.83E-07 9 309.39 118.92 0.96 

Beryllium C3-v0 2.88E-04 2.89E-04 2.95E-04 2.81E-04 1 2.45 2.78 0.00 

Cadmium C3-v0 1.11E-03 1.08E-03 1.33E-03 9.15E-04 1 18.76 21.23 1.00 

Chromium (Hex) C3-v0 2.43E-03 2.48E-03 2.51E-03 2.30E-03 1 4.62 5.23 0.00 

Chromium (Total) C3-v0 1.20E-03 7.38E-04 2.16E-03 7.03E-04 1 69.39 78.52 0.60 

Chrysene A2-v0 1.66E-06 1.29E-06 5.37E-06 9.83E-07 4 76.71 45.33 0.63 

Copper C3-v0 4.73E-03 2.16E-03 1.05E-02 1.48E-03 1 106.76 120.81 1.00 

Dibenz(a,h)anthracene A1-v2 1.06E-05 1.95E-06 1.31E-04 6.78E-07 9 262.22 100.79 0.00 

Ethylbenzene A2-v1 3.04E-02 1.74E-02 9.50E-02 2.53E-03 4 100.75 57.01 0.51 

Fluoranthene A2-v0 3.06E-06 3.03E-06 5.66E-06 1.72E-06 4 37.95 22.43 1.00 

Fluorene A2-v0 1.06E-05 8.55E-06 2.64E-05 3.33E-06 4 67.66 39.98 1.00 

Formaldehyde B1-v3 1.51E-01 3.03E-02 1.76E+00 7.92E-04 7 254.14 108.70 1.00 

Hydrogen Sulfide A1-v1 4.05E-01 3.27E-01 1.20E+00 1.82E-02 7 84.49 36.13 0.00 

Indeno(1,2,3-cd)pyrene A1-v3 1.15E-04 2.29E-06 1.55E-03 9.83E-07 9 342.12 131.50 0.99 

Lead C3-v0 5.49E-03 4.43E-03 8.43E-03 3.61E-03 1 47.03 53.22 1.00 

Manganese C3-v0 7.65E-03 7.03E-03 1.37E-02 2.21E-03 1 75.45 85.38 1.00 

Mercury C3-v0 2.02E-04 1.97E-04 2.17E-04 1.92E-04 1 6.49 7.34 0.36 

Naphthalene A2-v0 3.02E-04 2.43E-04 6.96E-04 1.33E-04 4 62.74 37.08 1.00 

Nickel C3-v1 1.06E-02 1.48E-03 2.88E-02 1.44E-03 1 149.30 168.95 0.95 

Phenanthrene A2-v0 1.44E-05 1.49E-05 2.17E-05 7.69E-06 4 32.45 19.18 1.00 

Phenol C1-v1 6.96E-03 4.70E-03 2.68E-02 2.93E-04 7 103.61 44.32 0.97 

Phosphorus C3-v0 7.21E-04 7.22E-04 7.38E-04 7.03E-04 1 2.45 2.78 0.00 

Propylene A2-v0 2.05E-03 2.14E-03 2.91E-03 1.00E-03 3 25.36 16.57 0.05 

Pyrene A2-v0 2.84E-06 2.63E-06 5.09E-06 1.78E-06 4 33.95 20.06 1.00 

Selenium C3-v0 2.20E-05 2.28E-05 2.85E-05 1.48E-05 1 31.23 35.34 0.78 

(continued) 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-37 

Table D-12a. Summary of Data for Emission Factor Development – Heaters Firing Refinery 

Fuel Gas Controlled with Selective Catalytic Reduction (continued) 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Silver C3-v1 1.81E-03 1.48E-03 3.61E-03 3.53E-04 1 91.23 103.24 0.94 

Thallium C3-v0 6.49E-03 6.49E-03 6.64E-03 6.33E-03 1 2.45 2.78 0.00 

Toluene D1-v2 1.37E-01 7.81E-02 1.21E+00 3.71E-03 11 154.31 52.65 0.55 

Xylene (Total) A2-v1 3.74E-02 3.37E-02 9.90E-02 4.27E-03 4 95.86 54.24 0.60 

Zinc C3-v0 2.34E-02 2.89E-02 3.18E-02 9.52E-03 1 51.72 58.53 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-38 

Table D-12b. Summary of Data for Emission Factor Development – Heaters Firing Refinery 

Fuel Gas Controlled with Selective Catalytic Reduction 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty,

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A2-v0 2.36E-09 1.55E-09 5.61E-09 1.20E-09 4 69.14 40.86 0.95 

Acenaphthylene A2-v0 1.55E-09 1.25E-09 2.74E-09 1.02E-09 4 41.70 24.64 0.51 

Acetaldehyde B1-v3 1.53E-05 8.12E-06 8.55E-05 8.41E-08 8 126.30 50.53 0.88 

Anthracene A2-v0 2.87E-09 2.30E-09 6.45E-09 1.09E-09 4 61.24 36.19 0.92 

Antimony C3-v0 5.17E-07 5.84E-07 7.58E-07 2.10E-07 1 54.13 61.25 1.00 

Arsenic C3-v0 8.50E-07 9.90E-07 1.28E-06 2.84E-07 1 60.10 68.00 1.00 

Barium C3-v0 5.78E-06 5.78E-06 5.92E-06 5.63E-06 1 2.45 2.78 0.00 

Benzene B1-v1 6.47E-05 5.49E-05 1.85E-04 2.54E-06 11 87.67 29.91 0.02 

Benzo(a)anthracene A1-v2 3.21E-08 5.40E-09 3.39E-07 1.05E-09 9 265.30 101.97 1.00 

Benzo(a)pyrene A1-v3 8.96E-08 1.73E-09 1.38E-06 1.02E-09 9 352.36 135.44 0.98 

Benzo(b)fluoranthene A1-v2 4.04E-08 3.31E-09 4.87E-07 1.02E-09 9 314.58 120.92 0.99 

Benzo(g,h,i)perylene A2-v0 1.17E-09 1.10E-09 1.40E-09 1.02E-09 4 11.55 6.82 0.00 

Benzo(k)fluoranthene A1-v2 2.41E-08 2.18E-09 2.96E-07 1.02E-09 9 310.01 119.16 0.96 

Beryllium C3-v0 2.57E-07 2.57E-07 2.63E-07 2.50E-07 1 2.45 2.78 0.00 

Cadmium C3-v0 9.88E-07 9.65E-07 1.18E-06 8.15E-07 1 18.76 21.23 1.00 

Chromium (Hex) C3-v0 2.17E-06 2.21E-06 2.24E-06 2.05E-06 1 4.62 5.23 0.00 

Chromium (Total) C3-v0 1.07E-06 6.57E-07 1.93E-06 6.26E-07 1 69.39 78.52 0.60 

Chrysene A2-v0 1.63E-09 1.23E-09 4.79E-09 1.02E-09 4 66.84 39.50 0.63 

Copper C3-v0 4.21E-06 1.93E-06 9.39E-06 1.31E-06 1 106.76 120.81 1.00 

Dibenz(a,h)anthracene A1-v2 1.02E-08 1.60E-09 1.37E-07 5.93E-10 9 279.09 107.28 0.00 

Ethylbenzene A2-v1 3.02E-05 1.79E-05 1.03E-04 2.72E-06 4 104.65 59.21 0.51 

Fluoranthene A2-v0 3.06E-09 3.14E-09 5.04E-09 1.85E-09 4 33.80 19.97 1.00 

Fluorene A2-v0 1.08E-08 8.77E-09 2.74E-08 2.96E-09 4 70.62 41.74 1.00 

Formaldehyde B1-v3 1.11E-04 1.90E-05 1.34E-03 7.67E-07 7 262.94 112.46 1.00 

Hydrogen Sulfide A1-v1 2.92E-04 2.46E-04 8.04E-04 1.76E-05 7 75.53 32.30 0.00 

Indeno(1,2,3-

cd)pyrene A1-v3 1.03E-07 1.75E-09 1.42E-06 1.02E-09 9 343.01 131.85 0.99 

Lead C3-v0 4.89E-06 3.94E-06 7.51E-06 3.21E-06 1 47.03 53.22 1.00 

Manganese C3-v0 6.81E-06 6.26E-06 1.22E-05 1.97E-06 1 75.45 85.38 1.00 

Mercury C3-v0 1.80E-07 1.75E-07 1.93E-07 1.71E-07 1 6.49 7.34 0.36 

Naphthalene A2-v0 3.13E-07 2.61E-07 7.58E-07 1.19E-07 4 66.90 39.53 1.00 

Nickel C3-v1 9.42E-06 1.31E-06 2.57E-05 1.29E-06 1 149.30 168.95 0.95 

Phenanthrene A2-v0 1.46E-08 1.50E-08 2.25E-08 6.91E-09 4 32.60 19.27 1.00 

Phenol C1-v1 5.63E-06 3.14E-06 2.54E-05 2.84E-07 7 114.62 49.02 0.97 

Phosphorus C3-v0 6.42E-07 6.43E-07 6.57E-07 6.26E-07 1 2.45 2.78 0.00 

Propylene A2-v0 2.17E-06 2.22E-06 2.98E-06 1.08E-06 3 23.69 15.47 0.05 

Pyrene A2-v0 2.84E-09 2.72E-09 4.53E-09 1.87E-09 4 28.87 17.06 1.00 

(continued) 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-39 

Table D-12b. Summary of Data for Emission Factor Development – Heaters Firing Refinery 

Fuel Gas Controlled with Selective Catalytic Reduction (continued) 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty,

% 

Detect 

Mean Median Maximum Minimum Ratio 

Selenium C3-v0 1.96E-08 2.03E-08 2.54E-08 1.32E-08 1 31.23 35.34 0.78 

Silver C3-v1 1.61E-06 1.31E-06 3.21E-06 3.14E-07 1 91.23 103.24 0.94 

Thallium C3-v0 5.78E-06 5.78E-06 5.92E-06 5.63E-06 1 2.45 2.78 0.00 

Toluene D1-v2 1.07E-04 7.00E-05 9.19E-04 4.04E-06 11 148.57 50.69 0.55 

Xylene (Total) A2-v1 3.73E-05 3.16E-05 1.08E-04 4.66E-06 4 99.32 56.19 0.60 

Zinc C3-v0 2.08E-05 2.58E-05 2.83E-05 8.48E-06 1 51.72 58.53 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-40 

Table D-13a. Summary of Data for Emission Factor Development – 

Internal Combustion Engines Firing Diesel Fuel, O2 < 13% 

Substance 

CARB 

Rating 

Emission Factor (lb/Mgal) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene C3-v0 6.44E-04 6.87E-04 8.67E-04 3.78E-04 1 38.39 43.44 1.00 

Acenaphthylene C3-v0 1.27E-03 1.31E-03 1.32E-03 1.18E-03 1 6.10 6.91 1.00 

Acetaldehyde A3-v0 3.47E-03 2.25E-03 6.46E-03 1.69E-03 1 75.34 85.25 1.00 

Acrolein A3-v0 1.07E-03 7.15E-04 1.79E-03 7.15E-04 1 57.74 65.33 0.56 

Anthracene C3-v0 1.70E-04 1.34E-04 2.89E-04 8.61E-05 1 62.56 70.79 1.00 

Benzene A3-v0 1.01E-01 9.93E-02 1.04E-01 9.93E-02 1 2.71 3.06 1.00 

Benzo(a)anthracene C3-v0 8.71E-05 8.30E-05 9.69E-05 8.15E-05 1 9.72 11.00 1.00 

Benzo(a)pyrene C3-v0 3.54E-05 3.84E-05 4.77E-05 2.00E-05 1 39.85 45.09 0.45 

Benzo(b)fluoranthene C3-v0 1.53E-04 1.41E-04 1.92E-04 1.26E-04 1 22.58 25.55 0.27 

Benzo(g,h,i)perylene C3-v0 7.69E-05 7.84E-05 8.30E-05 6.92E-05 1 9.17 10.37 1.00 

Benzo(k)fluoranthene C3-v0 3.02E-05 1.23E-05 6.92E-05 9.22E-06 1 111.67 126.37 0.76 

Chrysene C3-v0 2.11E-04 2.21E-04 2.28E-04 1.84E-04 1 11.03 12.48 1.00 

Dibenz(a,h)anthracene C3-v0 4.77E-05 4.61E-05 5.07E-05 4.61E-05 1 5.59 6.32 0.00 

Fluoranthene C3-v0 5.56E-04 5.47E-04 5.84E-04 5.37E-04 1 4.50 5.09 1.00 

Fluorene C3-v0 1.77E-03 1.76E-03 1.81E-03 1.72E-03 1 2.62 2.96 1.00 

Formaldehyde A3-v1 1.09E-02 4.64E-03 2.63E-02 1.74E-03 1 123.19 139.41 1.00 

Indeno(1,2,3-cd)pyrene C3-v0 5.69E-05 5.84E-05 6.61E-05 4.61E-05 1 17.72 20.05 0.34 

Naphthalene C3-v0 1.80E-02 1.81E-02 1.85E-02 1.72E-02 1 3.74 4.24 1.00 

Phenanthrene C3-v0 5.62E-03 5.65E-03 5.76E-03 5.47E-03 1 2.58 2.92 1.00 

Propylene A3-v0 3.85E-01 4.03E-01 4.03E-01 3.49E-01 1 8.06 9.12 1.00 

Pyrene C3-v0 5.11E-04 4.89E-04 5.60E-04 4.86E-04 1 8.16 9.24 1.00 

Toluene A3-v0 3.74E-02 3.70E-02 3.87E-02 3.64E-02 1 3.27 3.70 1.00 

Xylene (Total) A3-v0 2.68E-02 2.70E-02 2.77E-02 2.57E-02 1 3.85 4.36 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-41 

Table D-13b. Summary of Data for Emission Factor Development – 

Internal Combustion Engines Firing Diesel Fuel, O2 < 13% 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene C3-v0 4.54E-06 4.85E-06 6.12E-06 2.67E-06 1 38.39 43.44 1.00 

Acenaphthylene C3-v0 8.97E-06 9.23E-06 9.34E-06 8.34E-06 1 6.10 6.91 1.00 

Acetaldehyde A3-v0 2.44E-05 1.59E-05 4.56E-05 1.19E-05 1 75.34 85.25 1.00 

Acrolein A3-v0 7.57E-06 5.04E-06 1.26E-05 5.04E-06 1 57.74 65.33 0.56 

Anthracene C3-v0 1.20E-06 9.43E-07 2.04E-06 6.07E-07 1 62.56 70.79 1.00 

Benzene A3-v0 7.11E-04 7.00E-04 7.33E-04 7.00E-04 1 2.71 3.06 1.00 

Benzo(a)anthracene C3-v0 6.14E-07 5.85E-07 6.83E-07 5.75E-07 1 9.72 11.00 1.00 

Benzo(a)pyrene C3-v0 2.49E-07 2.71E-07 3.36E-07 1.41E-07 1 39.85 45.09 0.45 

Benzo(b)fluoranthene C3-v0 1.08E-06 9.98E-07 1.36E-06 8.89E-07 1 22.58 25.55 0.27 

Benzo(g,h,i)perylene C3-v0 5.42E-07 5.53E-07 5.85E-07 4.88E-07 1 9.17 10.37 1.00 

Benzo(k)fluoranthene C3-v0 2.13E-07 8.67E-08 4.88E-07 6.51E-08 1 111.67 126.37 0.76 

Chrysene C3-v0 1.49E-06 1.56E-06 1.60E-06 1.30E-06 1 11.03 12.48 1.00 

Dibenz(a,h)anthracene C3-v0 3.36E-07 3.25E-07 3.58E-07 3.25E-07 1 5.59 6.32 0.00 

Fluoranthene C3-v0 3.92E-06 3.86E-06 4.12E-06 3.78E-06 1 4.50 5.09 1.00 

Fluorene C3-v0 1.25E-05 1.24E-05 1.28E-05 1.21E-05 1 2.62 2.96 1.00 

Formaldehyde A3-v1 7.68E-05 3.27E-05 1.85E-04 1.23E-05 1 123.19 139.41 1.00 

Indeno(1,2,3-cd)pyrene C3-v0 4.01E-07 4.12E-07 4.66E-07 3.25E-07 1 17.72 20.05 0.34 

Naphthalene C3-v0 1.27E-04 1.28E-04 1.31E-04 1.21E-04 1 3.74 4.24 1.00 

Phenanthrene C3-v0 3.97E-05 3.98E-05 4.06E-05 3.86E-05 1 2.58 2.92 1.00 

Propylene A3-v0 2.71E-03 2.84E-03 2.84E-03 2.46E-03 1 8.06 9.12 1.00 

Pyrene C3-v0 3.61E-06 3.45E-06 3.95E-06 3.43E-06 1 8.16 9.24 1.00 

Toluene A3-v0 2.63E-04 2.61E-04 2.73E-04 2.57E-04 1 3.27 3.70 1.00 

Xylene (Total) A3-v0 1.89E-04 1.91E-04 1.95E-04 1.81E-04 1 3.85 4.36 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-42 

Table D-14a. Summary of Data for Emission Factor Development – 

Internal Combustion Engines Firing Diesel Fuel, O2 > 13% 

Substance 

CARB 

Rating 

Emission Factor (lb/Mgal) 

Tests RSD, % 

Uncertainty,

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene C3-v2 1.98E-04 1.15E-04 6.88E-04 1.41E-06 2 136.01 108.83 1.00 

Acenaphthylene C3-v3 7.03E-04 3.13E-04 1.86E-03 1.41E-06 2 125.21 100.19 1.00 

Acetaldehyde A3-v0 1.07E-01 1.07E-01 1.52E-01 5.82E-02 2 43.11 34.50 1.00 

Acrolein A3-v0 1.30E-02 8.43E-03 3.16E-02 6.62E-03 2 74.07 59.27 0.82 

Anthracene C3-v1 2.60E-04 2.95E-04 3.71E-04 3.11E-05 2 45.24 36.20 1.00 

Benzaldehyde A3-v0 1.26E-02 1.24E-02 1.35E-02 1.20E-02 1 6.29 7.12 0.68 

Benzene B3-v0 1.22E-01 1.13E-01 1.91E-01 6.57E-02 2 48.35 38.69 1.00 

Benzo(a)anthracene C3-v1 2.34E-04 2.04E-04 6.75E-04 1.55E-05 2 104.10 83.30 1.00 

Benzo(a)pyrene C3-v1 2.60E-05 1.82E-05 5.83E-05 1.41E-06 2 108.55 86.85 0.00 

Benzo(b)fluoranthene C3-v0 2.59E-05 2.72E-05 3.88E-05 1.17E-05 1 52.68 59.61 0.50 

Benzo(b+k)fluoranthene C3-v0 1.44E-06 1.45E-06 1.46E-06 1.41E-06 1 1.90 2.14 0.00 

Benzo(g,h,i)perylene C3-v1 6.78E-05 5.89E-05 1.55E-04 1.17E-05 2 71.76 57.42 0.43 

Benzo(k)fluoranthene C3-v0 4.14E-05 4.27E-05 6.22E-05 1.94E-05 1 51.63 58.43 0.50 

1,3-Butadiene C3-v0 5.41E-03 5.41E-03 5.41E-03 5.41E-03 1 0.00 0.00 0.00 

Chrysene C3-v0 4.90E-05 5.23E-05 6.75E-05 2.72E-05 2 33.96 27.17 1.00 

Dibenz(a,h)anthracene C3-v0 8.12E-05 6.41E-05 1.44E-04 4.42E-05 2 50.80 40.65 0.35 

Fluoranthene C3-v1 1.06E-03 8.29E-04 2.70E-03 6.99E-05 2 90.38 72.32 1.00 

Fluorene C3-v1 4.06E-03 3.96E-03 7.57E-03 2.10E-04 2 87.57 70.07 0.99 

Formaldehyde A3-v0 1.65E-01 1.45E-01 3.35E-01 8.55E-02 2 55.71 44.58 1.00 

Indeno(1,2,3-cd)pyrene C3-v1 6.43E-05 4.08E-05 1.32E-04 7.77E-06 2 83.82 67.07 0.30 

Naphthalene C3-v0 1.18E-02 7.84E-03 3.04E-02 5.92E-03 2 80.11 64.10 1.00 

Phenanthrene C3-v1 4.09E-03 4.23E-03 7.54E-03 3.11E-04 2 65.51 52.42 1.00 

Propylene B3-v0 3.58E-01 3.38E-01 5.83E-01 1.45E-01 2 56.61 45.30 1.00 

Pyrene C3-v0 6.66E-04 6.10E-04 1.07E-03 1.17E-04 2 51.99 41.60 1.00 

Toluene B3-v0 5.50E-02 5.49E-02 7.56E-02 3.44E-02 2 38.06 30.45 1.00 

Xylene (m,p) C3-v0 2.16E-02 2.09E-02 2.40E-02 1.98E-02 1 10.07 11.40 1.00 

Xylene (o) C3-v0 2.09E-02 2.09E-02 2.09E-02 2.09E-02 1 0.00 0.00 0.00 

Xylene (Total) A3-v0 3.59E-02 4.44E-02 4.44E-02 1.88E-02 1 41.24 46.67 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-43 

Table D-14b. Summary of Data for Emission Factor Development – 

Internal Combustion Engines Firing Diesel Fuel, O2 > 13% 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene C3-v2 1.43E-06 8.34E-07 4.97E-06 1.00E-08 2 136.02 108.84 1.00 

Acenaphthylene C3-v3 5.08E-06 2.27E-06 1.35E-05 1.00E-08 2 125.21 100.19 1.00 

Acetaldehyde A3-v0 7.64E-04 7.65E-04 1.08E-03 4.21E-04 2 42.48 33.99 1.00 

Acrolein A3-v0 9.37E-05 6.05E-05 2.29E-04 4.72E-05 2 74.63 59.71 0.82 

Anthracene C3-v1 1.86E-06 2.10E-06 2.65E-06 2.25E-07 2 45.07 36.07 1.00 

Benzaldehyde A3-v0 9.01E-05 8.84E-05 9.64E-05 8.54E-05 1 6.29 7.12 0.68 

Benzene B3-v0 8.81E-04 8.17E-04 1.38E-03 4.69E-04 2 48.96 39.17 1.00 

Benzo(a)anthracene C3-v1 1.67E-06 1.47E-06 4.81E-06 1.12E-07 2 103.79 83.05 1.00 

Benzo(a)pyrene C3-v1 1.88E-07 1.32E-07 4.21E-07 1.00E-08 2 108.63 86.92 0.00 

Benzo(b)fluoranthene C3-v0 1.87E-07 1.97E-07 2.81E-07 8.43E-08 1 52.68 59.61 0.50 

Benzo(b+k)fluoranthene C3-v0 1.03E-08 1.03E-08 1.04E-08 1.00E-08 1 1.90 2.14 0.00 

Benzo(g,h,i)perylene C3-v1 4.87E-07 4.24E-07 1.12E-06 8.43E-08 2 72.27 57.82 0.43 

Benzo(k)fluoranthene C3-v0 3.00E-07 3.09E-07 4.49E-07 1.40E-07 1 51.63 58.43 0.50 

1,3-Butadiene C3-v0 3.86E-05 3.86E-05 3.86E-05 3.86E-05 1 0.00 0.00 0.00 

Chrysene C3-v0 3.52E-07 3.76E-07 4.81E-07 1.97E-07 2 33.43 26.75 1.00 

Dibenz(a,h)anthracene C3-v0 5.84E-07 4.57E-07 1.04E-06 3.16E-07 2 51.34 41.08 0.35 

Fluoranthene C3-v1 7.59E-06 5.94E-06 1.93E-05 5.06E-07 2 90.02 72.03 1.00 

Fluorene C3-v1 2.90E-05 2.83E-05 5.40E-05 1.52E-06 2 87.31 69.86 0.99 

Formaldehyde A3-v0 1.19E-03 1.04E-03 2.39E-03 6.18E-04 2 55.30 44.25 1.00 

Indeno(1,2,3-cd)pyrene C3-v1 4.63E-07 2.91E-07 9.55E-07 5.62E-08 2 84.39 67.52 0.30 

Naphthalene C3-v0 8.48E-05 5.59E-05 2.20E-04 4.28E-05 2 80.69 64.56 1.00 

Phenanthrene C3-v1 2.93E-05 3.03E-05 5.38E-05 2.25E-06 2 65.09 52.08 1.00 

Propylene B3-v0 2.58E-03 2.44E-03 4.22E-03 1.04E-03 2 57.16 45.74 1.00 

Pyrene C3-v0 4.78E-06 4.38E-06 7.62E-06 8.43E-07 2 52.00 41.61 1.00 

Toluene B3-v0 3.96E-04 3.95E-04 5.47E-04 2.46E-04 2 38.72 30.98 1.00 

Xylene (m,p) C3-v0 1.54E-04 1.49E-04 1.71E-04 1.42E-04 1 10.07 11.40 1.00 

Xylene (o) C3-v0 1.49E-04 1.49E-04 1.49E-04 1.49E-04 1 0.00 0.00 0.00 

Xylene (Total) A3-v0 2.59E-04 3.21E-04 3.21E-04 1.36E-04 1 41.24 46.67 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-44 

Table D-15a. Summary of Data for Emission Factor Development – 

Two-Stroke Internal Combustion Engines Firing Field Gas, Lean 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A3-v0 7.41E-04 7.41E-04 1.08E-03 4.00E-04 1 65.08 90.19 0.00 

Acenaphthylene A3-v0 1.11E-02 1.11E-02 1.57E-02 6.44E-03 1 59.06 81.86 1.00 

Acetaldehyde A3-v0 8.77E+00 9.42E+00 1.14E+01 5.53E+00 1 33.90 38.37 1.00 

Acrolein A3-v1 2.00E+00 1.44E+00 4.36E+00 2.00E-01 1 106.79 120.84 1.00 

Anthracene A3-v0 4.50E-03 4.50E-03 6.67E-03 2.34E-03 1 67.84 94.02 1.00 

Benzene A3-v0 7.85E+00 4.60E+00 1.36E+01 4.23E+00 2 60.68 53.19 1.00 

Benzo(a)anthracene A3-v0 8.97E-04 8.97E-04 9.11E-04 8.83E-04 1 2.17 3.01 1.00 

Benzo(a)pyrene A3-v0 8.75E-04 8.75E-04 1.53E-03 2.16E-04 1 106.44 147.52 0.00 

Benzo(b)fluoranthene A3-v0 1.48E-04 1.48E-04 1.71E-04 1.24E-04 1 22.41 31.05 0.00 

Benzo(g,h,i)perylene A3-v0 9.40E-05 9.40E-05 9.92E-05 8.89E-05 1 7.74 10.72 0.00 

Benzo(k)fluoranthene A3-v0 4.57E-03 4.57E-03 4.69E-03 4.44E-03 1 3.78 5.23 1.00 

Chrysene A3-v0 1.69E-03 1.69E-03 1.80E-03 1.58E-03 1 9.43 13.07 1.00 

Dibenz(a,h)anthracene A3-v0 7.70E-05 7.70E-05 8.29E-05 7.11E-05 1 10.86 15.06 0.00 

Fluoranthene A3-v0 1.66E-04 1.66E-04 2.16E-04 1.16E-04 1 42.96 59.53 0.00 

Fluorene A3-v0 2.44E-03 2.44E-03 3.61E-03 1.27E-03 1 67.90 94.10 0.00 

Formaldehyde A3-v1 5.09E+01 6.79E+01 8.53E+01 4.21E+00 2 69.80 55.85 1.00 

Indeno(1,2,3-cd)pyrene A3-v0 1.37E-04 1.37E-04 1.46E-04 1.29E-04 1 8.83 12.24 0.00 

Naphthalene A3-v0 2.19E-01 2.19E-01 2.22E-01 2.16E-01 1 1.88 2.61 1.00 

Phenanthrene A3-v0 4.91E-03 4.91E-03 6.49E-03 3.33E-03 1 45.46 63.00 1.00 

Propylene A3-v0 2.49E+01 1.77E+01 4.02E+01 1.14E+01 2 56.74 49.73 1.00 

Pyrene A3-v0 2.39E-04 2.39E-04 3.06E-04 1.71E-04 1 40.10 55.57 0.64 

Toluene A3-v1 2.86E+00 2.36E+00 5.74E+00 2.23E-01 2 72.83 63.84 1.00 

Xylene (m,p) A3-v0 6.04E-01 3.17E-01 1.25E+00 1.89E-01 2 80.76 70.79 1.00 

Xylene (o) A3-v0 2.88E-01 1.36E-01 5.91E-01 6.80E-02 2 88.41 77.49 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-45 

Table D-15b. Summary of Data for Emission Factor Development – 

Two-Stroke Internal Combustion Engines Firing Field Gas, Lean 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A3-v0 7.06E-07 7.06E-07 1.03E-06 3.81E-07 1 65.08 90.19 0.00 

Acenaphthylene A3-v0 1.05E-05 1.05E-05 1.49E-05 6.14E-06 1 59.06 81.86 1.00 

Acetaldehyde A3-v0 8.36E-03 8.98E-03 1.08E-02 5.27E-03 1 33.90 38.37 1.00 

Acrolein A3-v1 1.90E-03 1.37E-03 4.15E-03 1.90E-04 1 106.79 120.84 1.00 

Anthracene A3-v0 4.29E-06 4.29E-06 6.35E-06 2.23E-06 1 67.84 94.02 1.00 

Benzene A3-v0 7.48E-03 4.38E-03 1.30E-02 4.03E-03 2 60.68 53.19 1.00 

Benzo(a)anthracene A3-v0 8.54E-07 8.54E-07 8.68E-07 8.41E-07 1 2.17 3.01 1.00 

Benzo(a)pyrene A3-v0 8.33E-07 8.33E-07 1.46E-06 2.06E-07 1 106.44 147.52 0.00 

Benzo(b)fluoranthene A3-v0 1.41E-07 1.41E-07 1.63E-07 1.18E-07 1 22.41 31.05 0.00 

Benzo(g,h,i)perylene A3-v0 8.95E-08 8.95E-08 9.44E-08 8.46E-08 1 7.74 10.72 0.00 

Benzo(k)fluoranthene A3-v0 4.35E-06 4.35E-06 4.46E-06 4.23E-06 1 3.78 5.23 1.00 

Chrysene A3-v0 1.61E-06 1.61E-06 1.72E-06 1.50E-06 1 9.43 13.07 1.00 

Dibenz(a,h)anthracene A3-v0 7.33E-08 7.33E-08 7.90E-08 6.77E-08 1 10.86 15.06 0.00 

Fluoranthene A3-v0 1.58E-07 1.58E-07 2.06E-07 1.10E-07 1 42.96 59.53 0.00 

Fluorene A3-v0 2.32E-06 2.32E-06 3.43E-06 1.21E-06 1 67.90 94.10 0.00 

Formaldehyde A3-v1 4.85E-02 6.46E-02 8.13E-02 4.01E-03 2 69.80 55.85 1.00 

Indeno(1,2,3-cd)pyrene A3-v0 1.31E-07 1.31E-07 1.39E-07 1.23E-07 1 8.83 12.24 0.00 

Naphthalene A3-v0 2.09E-04 2.09E-04 2.12E-04 2.06E-04 1 1.88 2.61 1.00 

Phenanthrene A3-v0 4.68E-06 4.68E-06 6.18E-06 3.17E-06 1 45.46 63.00 1.00 

Propylene A3-v0 2.37E-02 1.69E-02 3.82E-02 1.09E-02 2 56.74 49.73 1.00 

Pyrene A3-v0 2.27E-07 2.27E-07 2.92E-07 1.63E-07 1 40.10 55.57 0.64 

Toluene A3-v1 2.72E-03 2.25E-03 5.47E-03 2.12E-04 2 72.83 63.84 1.00 

Xylene (m,p) A3-v0 5.75E-04 3.02E-04 1.19E-03 1.80E-04 2 80.76 70.79 1.00 

Xylene (o) A3-v0 2.74E-04 1.30E-04 5.63E-04 6.48E-05 2 88.41 77.49 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-46 

Table D-16a. Summary of Data for Emission Factor Development – 

Four-Stroke Internal Combustion Engines Firing Field Gas, Lean 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Benzene A2-v0 1.72E+00 2.07E+00 2.24E+00 9.25E-01 3 35.58 28.47 1.00 

Formaldehyde A2-v1 4.15E+01 3.14E+01 9.78E+01 4.62E+00 3 76.73 50.13 1.00 

Propylene A2-v0 1.59E+01 1.84E+01 2.02E+01 9.48E+00 3 30.49 24.40 1.00 

Toluene A2-v0 7.68E-01 9.38E-01 1.17E+00 2.69E-01 3 51.12 40.90 1.00 

Xylene (m,p) A2-v1 3.02E-01 1.90E-01 9.03E-01 7.74E-02 3 99.71 79.78 1.00 

Xylene (o) A2-v0 8.97E-02 9.57E-02 1.22E-01 6.13E-02 3 25.60 20.49 1.00 

Table D-16b. Summary of Data for Emission Factor Development – 

Four-Stroke Internal Combustion Engines Firing Field Gas, Lean 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Benzene A2-v0 1.64E-03 1.97E-03 2.14E-03 8.81E-04 3 35.58 28.47 1.00 

Formaldehyde A2-v1 3.95E-02 2.99E-02 9.32E-02 4.40E-03 3 76.73 50.13 1.00 

Propylene A2-v0 1.52E-02 1.75E-02 1.92E-02 9.03E-03 3 30.49 24.40 1.00 

Toluene A2-v0 7.31E-04 8.94E-04 1.11E-03 2.56E-04 3 51.12 40.90 1.00 

Xylene (m,p) A2-v1 2.87E-04 1.81E-04 8.60E-04 7.37E-05 3 99.71 79.78 1.00 

Xylene (o) A2-v0 8.55E-05 9.11E-05 1.16E-04 5.84E-05 3 25.60 20.49 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-47 

Table D-17a. Summary of Data for Emission Factor Development – 

Four-Stroke Internal Combustion Engines Firing Field Gas, Rich 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Benzene A3-v0 1.10E+01 1.10E+01 1.11E+01 1.09E+01 1 1.15 1.59 1.00 

Formaldehyde A3-v0 5.05E+00 4.65E+00 5.98E+00 4.53E+00 1 15.91 18.00 1.00 

Propylene A3-v0 3.04E+00 3.04E+00 3.04E+00 3.04E+00 1 0.00 0.00 0.00 

Toluene A3-v0 3.44E+00 3.44E+00 3.55E+00 3.33E+00 1 4.56 6.32 1.00 

Xylene (m,p) A3-v0 5.37E-01 5.37E-01 5.62E-01 5.11E-01 1 6.73 9.33 1.00 

Xylene (o) A3-v0 2.68E-01 2.68E-01 2.81E-01 2.56E-01 1 6.73 9.33 1.00 

Table D-17b. Summary of Data for Emission Factor Development – 

Four-Stroke Internal Combustion Engines Firing Field Gas, Rich 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Benzene A3-v0 1.05E-02 1.05E-02 1.06E-02 1.04E-02 1 1.15 1.59 1.00 

Formaldehyde A3-v0 4.81E-03 4.43E-03 5.69E-03 4.31E-03 1 15.91 18.00 1.00 

Propylene A3-v0 2.90E-03 2.90E-03 2.90E-03 2.90E-03 1 0.00 0.00 0.00 

Toluene A3-v0 3.28E-03 3.28E-03 3.38E-03 3.17E-03 1 4.56 6.32 1.00 

Xylene (m,p) A3-v0 5.11E-04 5.11E-04 5.36E-04 4.87E-04 1 6.73 9.33 1.00 

Xylene (o) A3-v0 2.56E-04 2.56E-04 2.68E-04 2.43E-04 1 6.73 9.33 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-48 

Table D-18a. Summary of Data for Emission Factor Development – 

Four-Stroke Internal Combustion Engines Firing Natural Gas, Lean 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A3-v0 7.17E-04 6.36E-04 9.60E-04 5.57E-04 1 29.79 33.71 1.00 

Acenaphthylene A3-v0 7.59E-03 7.65E-03 1.07E-02 4.40E-03 1 41.56 47.03 1.00 

Acetaldehyde A1-v0 3.99E+00 2.96E+00 9.94E+00 1.52E+00 5 64.91 32.85 1.00 

Acrolein A1-v1 1.63E+00 1.10E+00 5.48E+00 2.01E-01 5 92.02 48.20 1.00 

Anthracene A3-v0 2.56E-04 2.40E-04 3.69E-04 1.60E-04 1 41.20 46.62 1.00 

Benzene A1-v1 1.21E+00 1.22E+00 2.47E+00 2.47E-01 7 47.28 24.77 1.00 

Benzo(a)anthracene A3-v0 7.78E-05 7.83E-05 9.60E-05 5.91E-05 1 23.70 26.82 1.00 

Benzo(a)pyrene A3-v0 3.55E-05 2.93E-05 5.17E-05 2.54E-05 1 39.97 45.23 0.76 

Benzo(b)fluoranthene A3-v2 3.27E-04 4.43E-05 9.29E-04 6.26E-06 1 159.90 180.94 0.95 

Benzo(g,h,i)perylene A3-v1 1.03E-04 2.93E-05 2.58E-04 2.09E-05 1 131.00 148.24 1.00 

Benzo(k)fluoranthene A3-v1 5.30E-04 4.87E-04 1.07E-03 3.08E-05 1 98.44 111.40 0.98 

Chrysene A3-v0 9.64E-05 1.11E-04 1.12E-04 6.61E-05 1 27.27 30.86 1.00 

Dibenz(a,h)anthracene A3-v0 1.09E-05 1.11E-05 1.47E-05 6.96E-06 1 35.41 40.07 1.00 

Fluoranthene A3-v0 2.50E-04 2.64E-04 3.32E-04 1.53E-04 1 36.21 40.98 1.00 

Fluorene A3-v0 4.60E-04 4.16E-04 6.28E-04 3.37E-04 1 32.63 36.92 0.00 

Formaldehyde A1-v0 2.87E+01 2.77E+01 4.79E+01 9.68E+00 7 38.56 16.49 1.00 

Indeno(1,2,3-cd)pyrene A3-v1 1.20E-04 3.91E-05 2.95E-04 2.43E-05 1 127.40 144.16 1.00 

Naphthalene A3-v0 1.22E-01 1.60E-01 1.86E-01 1.99E-02 1 73.21 82.85 1.00 

Phenanthrene A3-v0 8.93E-04 8.31E-04 1.26E-03 5.91E-04 1 37.66 42.62 1.00 

Propylene A1-v1 1.87E+01 8.81E+00 5.85E+01 4.12E+00 7 109.05 57.12 0.97 

Pyrene A3-v0 1.23E-04 1.42E-04 1.62E-04 6.61E-05 1 41.10 46.51 1.00 

Toluene A1-v0 4.12E-01 3.96E-01 5.70E-01 1.65E-01 7 33.98 17.80 1.00 

Xylene (m,p) A1-v0 8.63E-02 8.13E-02 1.59E-01 3.53E-02 7 46.27 24.24 1.00 

Xylene (o) A1-v0 4.94E-02 4.95E-02 9.14E-02 1.06E-02 7 39.52 20.70 0.95 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-49 

Table D-18b. Summary of Data for Emission Factor Development – 

Four-Stroke Internal Combustion Engines Firing Natural Gas, Lean 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A3-v0 6.83E-07 6.06E-07 9.14E-07 5.30E-07 1 29.79 33.71 1.00 

Acenaphthylene A3-v0 7.23E-06 7.29E-06 1.02E-05 4.19E-06 1 41.56 47.03 1.00 

Acetaldehyde A1-v0 3.80E-03 2.82E-03 9.47E-03 1.45E-03 5 64.91 32.85 1.00 

Acrolein A1-v1 1.56E-03 1.05E-03 5.22E-03 1.92E-04 5 92.02 48.20 1.00 

Anthracene A3-v0 2.44E-07 2.28E-07 3.52E-07 1.52E-07 1 41.20 46.62 1.00 

Benzene A1-v1 1.15E-03 1.17E-03 2.35E-03 2.35E-04 7 47.28 24.77 1.00 

Benzo(a)anthracene A3-v0 7.41E-08 7.45E-08 9.14E-08 5.63E-08 1 23.70 26.82 1.00 

Benzo(a)pyrene A3-v0 3.38E-08 2.79E-08 4.92E-08 2.42E-08 1 39.97 45.23 0.76 

Benzo(b)fluoranthene A3-v2 3.11E-07 4.22E-08 8.85E-07 5.96E-09 1 159.90 180.94 0.95 

Benzo(g,h,i)perylene A3-v1 9.80E-08 2.79E-08 2.46E-07 1.99E-08 1 131.00 148.24 1.00 

Benzo(k)fluoranthene A3-v1 5.04E-07 4.64E-07 1.02E-06 2.93E-08 1 98.44 111.40 0.98 

Chrysene A3-v0 9.19E-08 1.05E-07 1.07E-07 6.29E-08 1 27.27 30.86 1.00 

Dibenz(a,h)anthracene A3-v0 1.04E-08 1.05E-08 1.40E-08 6.63E-09 1 35.41 40.07 1.00 

Fluoranthene A3-v0 2.38E-07 2.52E-07 3.16E-07 1.46E-07 1 36.21 40.98 1.00 

Fluorene A3-v0 4.38E-07 3.96E-07 5.98E-07 3.21E-07 1 32.63 36.92 0.00 

Formaldehyde A1-v0 2.73E-02 2.64E-02 4.56E-02 9.22E-03 7 38.56 16.49 1.00 

Indeno(1,2,3-cd)pyrene A3-v1 1.14E-07 3.73E-08 2.81E-07 2.32E-08 1 127.40 144.16 1.00 

Naphthalene A3-v0 1.16E-04 1.52E-04 1.77E-04 1.90E-05 1 73.21 82.85 1.00 

Phenanthrene A3-v0 8.50E-07 7.92E-07 1.20E-06 5.63E-07 1 37.66 42.62 1.00 

Propylene A1-v1 1.78E-02 8.39E-03 5.57E-02 3.92E-03 7 109.05 57.12 0.97 

Pyrene A3-v0 1.18E-07 1.35E-07 1.55E-07 6.29E-08 1 41.10 46.51 1.00 

Toluene A1-v0 3.92E-04 3.77E-04 5.43E-04 1.57E-04 7 33.98 17.80 1.00 

Xylene (m,p) A1-v0 8.22E-05 7.74E-05 1.51E-04 3.36E-05 7 46.27 24.24 1.00 

Xylene (o) A1-v0 4.71E-05 4.71E-05 8.70E-05 1.01E-05 7 39.52 20.70 0.95 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-50 

Table D-19a. Summary of Data for Emission Factor Development – 

Four-Stroke Internal Combustion Engines Firing Natural Gas, Rich 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acetaldehyde A3-v0 1.71E+00 1.70E+00 1.82E+00 1.60E+00 1 6.46 7.31 1.00 

Acrolein A3-v2 5.40E-01 4.16E-01 1.37E+00 2.59E-03 2 105.82 84.67 1.00 

Benzene A3-v0 9.87E+00 9.87E+00 1.02E+01 9.51E+00 1 5.05 7.00 1.00 

Formaldehyde A3-v1 5.32E+00 4.48E+00 1.14E+01 4.21E-01 2 100.69 80.57 1.00 

Propylene A3-v0 3.95E+01 3.95E+01 4.20E+01 3.70E+01 1 8.95 12.40 1.00 

Toluene A3-v0 2.51E+00 2.51E+00 2.62E+00 2.41E+00 1 6.15 8.52 1.00 

Xylene (m,p) A3-v0 4.41E-01 4.41E-01 4.54E-01 4.28E-01 1 4.04 5.60 1.00 

Xylene (o) A3-v0 2.17E-01 2.17E-01 2.22E-01 2.12E-01 1 3.29 4.56 1.00 

Table D-19b. Summary of Data for Emission Factor Development – 

Four-Stroke Internal Combustion Engines Firing Natural Gas, Rich 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acetaldehyde A3-v0 1.63E-03 1.62E-03 1.74E-03 1.53E-03 1 6.46 7.31 1.00 

Acrolein A3-v2 5.15E-04 3.97E-04 1.31E-03 2.50E-06 2 105.65 84.54 1.00 

Benzene A3-v0 9.40E-03 9.40E-03 9.73E-03 9.06E-03 1 5.05 7.00 1.00 

Formaldehyde A3-v1 5.07E-03 4.27E-03 1.09E-02 4.08E-04 2 100.52 80.43 1.00 

Propylene A3-v0 3.76E-02 3.76E-02 4.00E-02 3.52E-02 1 8.95 12.40 1.00 

Toluene A3-v0 2.40E-03 2.40E-03 2.50E-03 2.29E-03 1 6.15 8.52 1.00 

Xylene (m,p) A3-v0 4.20E-04 4.20E-04 4.32E-04 4.08E-04 1 4.04 5.60 1.00 

Xylene (o) A3-v0 2.06E-04 2.06E-04 2.11E-04 2.02E-04 1 3.29 4.56 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-51 

Table D-20a. Summary of Data for Emission Factor Development – 

Steam Generators Firing Natural Gas 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acetaldehyde A3-v0 1.56E-02 1.57E-02 1.66E-02 1.44E-02 1 7.27 8.22 1.00 

Acrolein A3-v0 1.84E-02 1.75E-02 2.22E-02 1.55E-02 1 18.73 21.19 1.00 

Benzene B3-v0 3.86E-03 3.87E-03 3.88E-03 3.83E-03 2 0.57 0.46 0.00 

Formaldehyde A3-v1 2.95E-02 1.83E-02 9.16E-02 3.96E-03 2 111.23 89.00 1.00 

Propylene C3-v0 1.09E-01 1.09E-01 1.09E-01 1.09E-01 1 0.36 0.41 0.00 

Toluene B3-v0 1.20E-02 1.20E-02 1.20E-02 1.19E-02 2 0.57 0.46 0.00 

Xylene (Total) B3-v0 2.76E-02 2.76E-02 2.77E-02 2.74E-02 2 0.57 0.46 0.00 

Table D-20b. Summary of Data for Emission Factor Development – 

Steam Generators Firing Natural Gas 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acetaldehyde A3-v0 1.66E-05 1.68E-05 1.77E-05 1.53E-05 1 7.27 8.22 1.00 

Acrolein A3-v0 1.96E-05 1.86E-05 2.37E-05 1.65E-05 1 18.73 21.19 1.00 

Benzene B3-v0 3.94E-06 3.93E-06 4.10E-06 3.78E-06 2 4.28 3.42 0.00 

Formaldehyde A3-v1 3.11E-05 1.87E-05 9.75E-05 3.87E-06 2 113.45 90.78 1.00 

Propylene C3-v0 1.16E-04 1.16E-04 1.17E-04 1.16E-04 1 0.36 0.41 0.00 

Toluene B3-v0 1.22E-05 1.22E-05 1.27E-05 1.17E-05 2 4.28 3.42 0.00 

Xylene (Total) B3-v0 2.81E-05 2.81E-05 2.94E-05 2.70E-05 2 4.28 3.42 0.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-52 

Table D-21a. Summary of Data for Emission Factor Development – 

Steam Generators Firing Natural Gas and Casing Vapor Recovery Gas 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A3-v0 1.04E-06 7.23E-07 2.38E-06 4.12E-07 2 69.67 55.75 0.72 

Acenaphthylene A3-v1 2.70E-06 6.70E-07 1.03E-05 4.12E-07 2 144.60 115.70 0.85 

Acetaldehyde A2-v0 1.12E-02 1.02E-02 2.67E-02 5.02E-03 4 55.73 31.53 0.84 

Acrolein A2-v0 1.05E-02 1.07E-02 1.82E-02 5.02E-03 4 37.86 21.42 0.88 

Anthracene A3-v0 2.09E-06 2.28E-06 3.82E-06 4.12E-07 2 62.45 49.97 0.97 

Benzene B1-v0 3.33E-03 2.68E-03 6.21E-03 2.36E-03 5 44.41 22.47 0.00 

Benzo(a)anthracene A3-v0 1.22E-06 1.12E-06 2.16E-06 6.82E-07 2 40.32 32.26 0.45 

Benzo(a)pyrene A3-v0 6.86E-07 6.46E-07 1.33E-06 3.98E-07 2 49.51 39.61 0.32 

Benzo(b)fluoranthene A3-v0 2.00E-06 9.18E-07 4.78E-06 6.36E-07 2 95.49 76.41 0.84 

Benzo(g,h,i)perylene A3-v0 9.80E-07 6.70E-07 1.75E-06 4.12E-07 2 61.38 49.11 0.59 

Benzo(k)fluoranthene A3-v0 8.21E-07 6.70E-07 1.39E-06 4.12E-07 2 44.95 35.97 0.52 

Chrysene A3-v0 1.55E-06 1.83E-06 2.16E-06 6.82E-07 2 38.63 30.91 0.33 

Dibenz(a,h)anthracene A3-v0 5.30E-07 5.24E-07 6.82E-07 3.96E-07 2 26.65 21.32 0.00 

Ethylbenzene A3-v0 9.22E-03 7.34E-03 1.86E-02 3.69E-03 2 55.96 44.77 0.54 

Fluoranthene A3-v0 3.66E-06 1.71E-06 9.03E-06 1.01E-06 2 98.55 78.86 1.00 

Fluorene A3-v0 5.63E-06 2.47E-06 1.30E-05 1.77E-06 2 95.48 76.40 1.00 

Formaldehyde A2-v1 1.58E-02 9.51E-03 7.01E-02 5.02E-03 4 117.82 66.66 0.70 

Hydrogen Sulfide C3-v0 1.48E-01 1.43E-01 2.28E-01 7.39E-02 1 51.99 58.83 1.00 

Indeno(1,2,3-cd)pyrene A3-v0 1.17E-06 6.70E-07 2.38E-06 4.12E-07 2 76.13 60.92 0.66 

Naphthalene A3-v0 2.89E-04 2.24E-04 5.54E-04 1.50E-04 2 56.04 44.84 1.00 

Phenanthrene A3-v0 1.64E-05 1.21E-05 3.17E-05 6.59E-06 2 64.15 51.33 1.00 

Propylene C2-v1 1.83E-01 7.80E-02 6.30E-01 6.71E-03 4 117.13 66.27 0.72 

Pyrene A3-v1 6.00E-06 2.78E-06 1.74E-05 8.19E-07 2 109.69 87.77 1.00 

Toluene B1-v0 1.37E-02 9.47E-03 3.08E-02 7.33E-03 5 59.41 30.07 0.64 

Xylene (Total) B1-v0 1.85E-02 1.70E-02 4.03E-02 1.11E-02 5 36.66 18.55 0.23 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-53 

Table D-21b. Summary of Data for Emission Factor Development – 

Steam Generators Firing Natural Gas and Casing Vapor Recovery Gas 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A3-v0 1.06E-09 7.84E-10 2.34E-09 4.06E-10 2 65.71 52.57 0.72 

Acenaphthylene A3-v1 2.69E-09 7.14E-10 1.01E-08 4.06E-10 2 142.14 113.73 0.85 

Acetaldehyde A2-v0 1.85E-05 1.68E-05 4.88E-05 5.47E-06 4 66.12 37.41 0.84 

Acrolein A2-v0 1.69E-05 1.92E-05 2.62E-05 5.47E-06 4 41.86 23.68 0.88 

Anthracene A3-v1 2.18E-09 2.33E-09 4.26E-09 4.06E-10 2 64.55 51.65 0.97 

Benzene B1-v0 4.45E-06 4.40E-06 6.12E-06 2.75E-06 5 23.61 11.95 0.00 

Benzo(a)anthracene A3-v0 1.28E-09 1.12E-09 2.42E-09 7.12E-10 2 45.67 36.54 0.45 

Benzo(a)pyrene A3-v0 7.08E-10 7.11E-10 1.31E-09 3.92E-10 2 47.05 37.64 0.32 

Benzo(b)fluoranthene A3-v0 2.01E-09 9.26E-10 4.71E-09 7.10E-10 2 92.63 74.12 0.84 

Benzo(g,h,i)perylene A3-v0 9.98E-10 7.14E-10 1.73E-09 4.06E-10 2 57.41 45.93 0.59 

Benzo(k)fluoranthene A3-v0 8.41E-10 7.14E-10 1.37E-09 4.06E-10 2 41.36 33.09 0.52 

Chrysene A3-v0 1.60E-09 1.80E-09 2.42E-09 7.12E-10 2 39.17 31.35 0.33 

Dibenz(a,h)anthracene A3-v0 5.54E-10 5.58E-10 7.15E-10 3.90E-10 2 31.29 25.04 0.00 

Ethylbenzene A3-v0 9.63E-06 7.23E-06 2.02E-05 4.02E-06 2 59.81 47.86 0.54 

Fluoranthene A3-v0 3.67E-09 1.78E-09 8.90E-09 1.07E-09 2 95.56 76.46 1.00 

Fluorene A3-v0 5.66E-09 2.64E-09 1.28E-08 1.85E-09 2 92.16 73.74 1.00 

Formaldehyde A2-v1 2.53E-05 1.56E-05 1.01E-04 5.47E-06 4 111.34 63.00 0.70 

Hydrogen Sulfide C3-v0 1.59E-04 1.60E-04 2.38E-04 8.02E-05 1 49.59 56.11 1.00 

Indeno(1,2,3-cd)pyrene A3-v0 1.18E-09 7.14E-10 2.34E-09 4.06E-10 2 72.24 57.80 0.66 

Naphthalene A3-v0 2.93E-07 2.33E-07 5.46E-07 1.57E-07 2 52.01 41.62 1.00 

Phenanthrene A3-v0 1.68E-08 1.34E-08 3.12E-08 6.50E-09 2 60.61 48.50 1.00 

Propylene C2-v1 2.29E-04 1.27E-04 6.83E-04 1.23E-05 4 94.36 53.39 0.72 

Pyrene A3-v1 6.02E-09 2.93E-09 1.72E-08 8.55E-10 2 106.75 85.42 1.00 

Toluene B1-v0 1.73E-05 1.43E-05 3.04E-05 1.34E-05 5 33.16 16.78 0.64 

Xylene (Total) B1-v0 2.66E-05 3.11E-05 4.36E-05 1.21E-05 5 36.70 18.57 0.23 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-54 

Table D-22a. Summary of Data for Emission Factor Development – 

Gas Turbines with No Duct Burners Firing Natural Gas 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A3-v0 3.39E-06 2.11E-06 8.87E-06 1.26E-06 2 88.62 70.91 0.67 

Acenaphthylene A3-v0 3.00E-06 2.87E-06 5.78E-06 1.26E-06 2 56.64 45.32 0.54 

Acetaldehyde A3-v0 3.96E-02 4.76E-02 5.38E-02 1.73E-02 1 49.40 55.90 0.85 

Acrolein A3-v0 1.81E-02 1.81E-02 1.82E-02 1.79E-02 1 0.68 0.77 0.00 

Anthracene A3-v1 3.52E-05 7.45E-06 1.53E-04 3.77E-06 2 167.76 134.23 1.00 

Benzene A3-v0 1.24E-02 1.23E-02 1.85E-02 6.96E-03 2 47.07 37.67 0.00 

Benzo(a)anthracene A3-v0 2.89E-06 2.39E-06 5.89E-06 1.84E-06 2 53.67 42.94 0.34 

Benzo(a)pyrene A3-v0 2.13E-06 2.09E-06 3.17E-06 1.26E-06 2 43.24 34.60 0.00 

Benzo(b)fluoranthene A3-v0 3.40E-06 2.87E-06 8.93E-06 1.26E-06 2 83.26 66.62 0.44 

Benzo(g,h,i)perylene A3-v0 2.47E-06 2.87E-06 3.31E-06 1.26E-06 2 37.62 30.10 0.22 

Benzo(k)fluoranthene A3-v0 2.67E-06 2.87E-06 4.54E-06 1.26E-06 2 46.39 37.12 0.28 

Chrysene A3-v0 5.08E-06 5.99E-06 6.34E-06 2.89E-06 2 31.73 25.39 0.31 

Dibenz(a,h)anthracene A3-v0 2.13E-06 2.09E-06 3.17E-06 1.26E-06 2 43.24 34.60 0.00 

Ethylbenzene A3-v0 1.53E-02 1.52E-02 2.20E-02 9.49E-03 2 40.90 32.72 0.00 

Fluoranthene A3-v0 1.20E-05 1.21E-05 1.74E-05 5.78E-06 2 36.16 28.93 1.00 

Fluorene A3-v0 1.55E-05 1.42E-05 3.17E-05 8.05E-06 2 54.85 43.89 1.00 

Formaldehyde A3-v0 2.09E-02 1.73E-02 2.81E-02 1.73E-02 1 29.80 33.72 0.45 

Indeno(1,2,3-cd)pyrene A3-v0 2.38E-06 2.82E-06 3.17E-06 1.26E-06 2 35.90 28.73 0.20 

Naphthalene A3-v0 7.51E-04 8.01E-04 9.51E-04 4.56E-04 2 28.73 22.99 1.00 

Phenanthrene A3-v0 6.71E-05 4.95E-05 1.46E-04 2.62E-05 2 64.08 51.28 1.00 

Propylene A3-v0 1.71E+00 1.68E+00 2.00E+00 1.46E+00 1 15.66 17.72 1.00 

Pyrene A3-v0 2.31E-05 2.09E-05 4.23E-05 5.78E-06 2 63.17 50.55 1.00 

Toluene A3-v1 7.17E-02 5.89E-02 1.68E-01 8.22E-03 2 88.92 71.15 0.98 

Xylene (Total) A3-v0 3.63E-02 4.11E-02 6.26E-02 9.70E-03 2 52.17 41.75 0.38 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-55 

Table D-22b. Summary of Data for Emission Factor Development – 

Gas Turbines with No Duct Burners Firing Natural Gas 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A3-v0 3.25E-09 2.03E-09 8.46E-09 1.23E-09 2 87.69 70.16 0.67 

Acenaphthylene A3-v0 2.90E-09 2.74E-09 5.67E-09 1.23E-09 2 57.20 45.77 0.54 

Acetaldehyde A3-v0 3.78E-05 4.55E-05 5.14E-05 1.65E-05 1 49.40 55.90 0.85 

Acrolein A3-v0 1.72E-05 1.73E-05 1.73E-05 1.71E-05 1 0.68 0.77 0.00 

Anthracene A3-v1 3.43E-08 7.19E-09 1.50E-07 3.70E-09 2 168.94 135.17 1.00 

Benzene A3-v0 1.20E-05 1.19E-05 1.82E-05 6.64E-06 2 48.32 38.66 0.00 

Benzo(a)anthracene A3-v0 2.78E-09 2.31E-09 5.62E-09 1.80E-09 2 52.46 41.98 0.34 

Benzo(a)pyrene A3-v0 2.05E-09 2.01E-09 3.02E-09 1.23E-09 2 41.94 33.56 0.00 

Benzo(b)fluoranthene A3-v0 3.30E-09 2.74E-09 8.77E-09 1.23E-09 2 84.51 67.62 0.44 

Benzo(g,h,i)perylene A3-v0 2.38E-09 2.74E-09 3.25E-09 1.23E-09 2 37.17 29.74 0.22 

Benzo(k)fluoranthene A3-v0 2.58E-09 2.74E-09 4.46E-09 1.23E-09 2 46.68 37.35 0.28 

Chrysene A3-v0 4.93E-09 5.88E-09 6.05E-09 2.76E-09 2 32.43 25.95 0.31 

Dibenz(a,h)anthracene A3-v0 2.05E-09 2.01E-09 3.02E-09 1.23E-09 2 41.94 33.56 0.00 

Ethylbenzene A3-v0 1.49E-05 1.48E-05 2.16E-05 9.05E-06 2 42.21 33.78 0.00 

Fluoranthene A3-v0 1.16E-08 1.16E-08 1.71E-08 5.51E-09 2 36.82 29.47 1.00 

Fluorene A3-v0 1.49E-08 1.40E-08 3.02E-08 7.90E-09 2 53.86 43.09 1.00 

Formaldehyde A3-v0 1.99E-05 1.65E-05 2.68E-05 1.65E-05 1 29.80 33.72 0.45 

Indeno(1,2,3-cd)pyrene A3-v0 2.29E-09 2.73E-09 3.02E-09 1.23E-09 2 35.08 28.07 0.20 

Naphthalene A3-v0 7.29E-07 7.77E-07 9.33E-07 4.35E-07 2 30.01 24.02 1.00 

Phenanthrene A3-v0 6.46E-08 4.86E-08 1.39E-07 2.57E-08 2 62.98 50.39 1.00 

Propylene A3-v0 1.63E-03 1.61E-03 1.90E-03 1.39E-03 1 15.66 17.72 1.00 

Pyrene A3-v0 2.25E-08 2.03E-08 4.15E-08 5.51E-09 2 64.16 51.34 1.00 

Toluene A3-v1 7.01E-05 5.75E-05 1.65E-04 7.85E-06 2 89.58 71.67 0.98 

Xylene (Total) A3-v0 3.52E-05 4.04E-05 5.97E-05 9.25E-06 2 51.95 41.57 0.38 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-56 

Table D-23a. Summary of Data for Emission Factor Development – 

Gas Turbines with No Duct Burners Firing Natural Gas Controlled with 

Selective Catalytic Reduction and Carbon Monoxide Oxidation Catalyst 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A3-v0 3.39E-06 2.11E-06 8.87E-06 1.26E-06 2 88.62 70.91 0.67 

Acenaphthylene A3-v0 3.00E-06 2.87E-06 5.78E-06 1.26E-06 2 56.64 45.32 0.54 

Acetaldehyde A3-v0 3.96E-02 4.76E-02 5.38E-02 1.73E-02 1 49.40 55.90 0.85 

Acrolein A3-v0 1.81E-02 1.81E-02 1.82E-02 1.79E-02 1 0.68 0.77 0.00 

Anthracene A3-v1 3.52E-05 7.45E-06 1.53E-04 3.77E-06 2 167.76 134.23 1.00 

Benzene A3-v0 1.24E-02 1.23E-02 1.85E-02 6.96E-03 2 47.07 37.67 0.00 

Benzo(a)anthracene A3-v0 2.89E-06 2.39E-06 5.89E-06 1.84E-06 2 53.67 42.94 0.34 

Benzo(a)pyrene A3-v0 2.13E-06 2.09E-06 3.17E-06 1.26E-06 2 43.24 34.60 0.00 

Benzo(b)fluoranthene A3-v0 3.40E-06 2.87E-06 8.93E-06 1.26E-06 2 83.26 66.62 0.44 

Benzo(g,h,i)perylene A3-v0 2.47E-06 2.87E-06 3.31E-06 1.26E-06 2 37.62 30.10 0.22 

Benzo(k)fluoranthene A3-v0 2.67E-06 2.87E-06 4.54E-06 1.26E-06 2 46.39 37.12 0.28 

Chrysene A3-v0 5.08E-06 5.99E-06 6.34E-06 2.89E-06 2 31.73 25.39 0.31 

Dibenz(a,h)anthracene A3-v0 2.13E-06 2.09E-06 3.17E-06 1.26E-06 2 43.24 34.60 0.00 

Ethylbenzene A3-v0 1.53E-02 1.52E-02 2.20E-02 9.49E-03 2 40.90 32.72 0.00 

Fluoranthene A3-v0 1.20E-05 1.21E-05 1.74E-05 5.78E-06 2 36.16 28.93 1.00 

Fluorene A3-v0 1.55E-05 1.42E-05 3.17E-05 8.05E-06 2 54.85 43.89 1.00 

Formaldehyde A3-v0 2.09E-02 1.73E-02 2.81E-02 1.73E-02 1 29.80 33.72 0.45 

Indeno(1,2,3-cd)pyrene A3-v0 2.38E-06 2.82E-06 3.17E-06 1.26E-06 2 35.90 28.73 0.20 

Naphthalene A3-v0 7.51E-04 8.01E-04 9.51E-04 4.56E-04 2 28.73 22.99 1.00 

Phenanthrene A3-v0 6.71E-05 4.95E-05 1.46E-04 2.62E-05 2 64.08 51.28 1.00 

Propylene A3-v0 1.71E+00 1.68E+00 2.00E+00 1.46E+00 1 15.66 17.72 1.00 

Pyrene A3-v0 2.31E-05 2.09E-05 4.23E-05 5.78E-06 2 63.17 50.55 1.00 

Toluene A3-v1 7.17E-02 5.89E-02 1.68E-01 8.22E-03 2 88.92 71.15 0.98 

Xylene (Total) A3-v0 3.63E-02 4.11E-02 6.26E-02 9.70E-03 2 52.17 41.75 0.38 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-57 

Table D-23b. Summary of Data for Emission Factor Development – 

Gas Turbines with No Duct Burners Firing Natural Gas Controlled with 

Selective Catalytic Reduction and Carbon Monoxide Oxidation Catalyst 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene A3-v0 3.25E-09 2.03E-09 8.46E-09 1.23E-09 2 87.69 70.16 0.67 

Acenaphthylene A3-v0 2.90E-09 2.74E-09 5.67E-09 1.23E-09 2 57.20 45.77 0.54 

Acetaldehyde A3-v0 3.78E-05 4.55E-05 5.14E-05 1.65E-05 1 49.40 55.90 0.85 

Acrolein A3-v0 1.72E-05 1.73E-05 1.73E-05 1.71E-05 1 0.68 0.77 0.00 

Anthracene A3-v1 3.43E-08 7.19E-09 1.50E-07 3.70E-09 2 168.94 135.17 1.00 

Benzene A3-v0 1.20E-05 1.19E-05 1.82E-05 6.64E-06 2 48.32 38.66 0.00 

Benzo(a)anthracene A3-v0 2.78E-09 2.31E-09 5.62E-09 1.80E-09 2 52.46 41.98 0.34 

Benzo(a)pyrene A3-v0 2.05E-09 2.01E-09 3.02E-09 1.23E-09 2 41.94 33.56 0.00 

Benzo(b)fluoranthene A3-v0 3.30E-09 2.74E-09 8.77E-09 1.23E-09 2 84.51 67.62 0.44 

Benzo(g,h,i)perylene A3-v0 2.38E-09 2.74E-09 3.25E-09 1.23E-09 2 37.17 29.74 0.22 

Benzo(k)fluoranthene A3-v0 2.58E-09 2.74E-09 4.46E-09 1.23E-09 2 46.68 37.35 0.28 

Chrysene A3-v0 4.93E-09 5.88E-09 6.05E-09 2.76E-09 2 32.43 25.95 0.31 

Dibenz(a,h)anthracene A3-v0 2.05E-09 2.01E-09 3.02E-09 1.23E-09 2 41.94 33.56 0.00 

Ethylbenzene A3-v0 1.49E-05 1.48E-05 2.16E-05 9.05E-06 2 42.21 33.78 0.00 

Fluoranthene A3-v0 1.16E-08 1.16E-08 1.71E-08 5.51E-09 2 36.82 29.47 1.00 

Fluorene A3-v0 1.49E-08 1.40E-08 3.02E-08 7.90E-09 2 53.86 43.09 1.00 

Formaldehyde A3-v0 1.99E-05 1.65E-05 2.68E-05 1.65E-05 1 29.80 33.72 0.45 

Indeno(1,2,3-cd)pyrene A3-v0 2.29E-09 2.73E-09 3.02E-09 1.23E-09 2 35.08 28.07 0.20 

Naphthalene A3-v0 7.29E-07 7.77E-07 9.33E-07 4.35E-07 2 30.01 24.02 1.00 

Phenanthrene A3-v0 6.46E-08 4.86E-08 1.39E-07 2.57E-08 2 62.98 50.39 1.00 

Propylene A3-v0 1.63E-03 1.61E-03 1.90E-03 1.39E-03 1 15.66 17.72 1.00 

Pyrene A3-v0 2.25E-08 2.03E-08 4.15E-08 5.51E-09 2 64.16 51.34 1.00 

Toluene A3-v1 7.01E-05 5.75E-05 1.65E-04 7.85E-06 2 89.58 71.67 0.98 

Xylene (Total) A3-v0 3.52E-05 4.04E-05 5.97E-05 9.25E-06 2 51.95 41.57 0.38 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-58 

Table D-24a. Summary of Data for Emission Factor Development – Gas Turbines with Duct 

Burners Firing Natural Gas Controlled with Selective Catalytic Reduction 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Formaldehyde C3-v0 6.22E+00 6.09E+00 6.87E+00 5.71E+00 1 9.57 10.83 1.00 

Table D-24b. Summary of Data for Emission Factor Development – Gas Turbines with Duct 

Burners Firing Natural Gas Controlled with Selective Catalytic Reduction 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Formaldehyde C3-v0 6.02E-03 5.89E-03 6.65E-03 5.52E-03 1 9.57 10.83 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-59 

Table D-25a. Summary of Data for Emission Factor Development – Gas Turbines with 

Duct Burners Firing Natural Gas and Refinery Fuel Gas Controlled with 

Selective Catalytic Reduction and Carbon Monoxide Oxidation Catalyst 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene C3-v0 2.37E-05 2.15E-05 3.82E-05 1.15E-05 1 56.84 64.32 1.00 

Acenaphthylene C3-v0 1.15E-05 1.29E-05 1.32E-05 8.53E-06 1 22.70 25.68 1.00 

Acetaldehyde A3-v0 4.54E-03 3.41E-03 6.83E-03 3.38E-03 1 43.72 49.48 1.00 

Anthracene C3-v0 2.66E-05 2.43E-05 3.66E-05 1.89E-05 1 34.03 38.51 1.00 

Benzene C3-v0 1.66E-01 1.68E-01 1.81E-01 1.46E-01 2 9.66 7.73 0.00 

Benzo(a)anthracene C3-v1 1.60E-05 3.47E-06 4.15E-05 3.03E-06 1 138.05 156.22 0.86 

Benzo(a)pyrene C3-v0 1.02E-05 1.05E-05 1.36E-05 6.63E-06 1 34.09 38.57 0.00 

Benzo(b)fluoranthene C3-v0 2.69E-05 3.19E-05 3.44E-05 1.45E-05 1 40.14 45.42 0.82 

Benzo(g,h,i)perylene C3-v0 2.06E-05 2.00E-05 2.71E-05 1.45E-05 1 30.62 34.65 0.00 

Benzo(k)fluoranthene C3-v0 1.34E-05 1.21E-05 2.00E-05 8.05E-06 1 45.53 51.52 0.00 

Cadmium C3-v0 2.08E-03 1.06E-03 4.16E-03 1.03E-03 1 86.47 97.85 0.67 

Chromium (Hex) C3-v0 7.46E-03 7.08E-03 1.50E-02 1.53E-03 2 83.96 67.18 0.00 

Chromium (Total) C3-v1 5.35E-02 3.36E-02 1.84E-01 1.51E-02 2 121.46 97.19 1.00 

Chrysene C3-v0 1.16E-04 6.85E-05 2.43E-04 3.47E-05 1 96.95 109.70 1.00 

Copper A3-v0 1.89E-03 1.98E-03 2.64E-03 1.04E-03 1 42.72 48.34 1.00 

Dibenz(a,h)anthracene C3-v0 7.10E-06 8.12E-06 8.59E-06 4.58E-06 1 30.92 34.99 0.00 

Fluoranthene C3-v0 1.06E-04 1.07E-04 1.58E-04 5.53E-05 1 48.01 54.33 1.00 

Fluorene C3-v1 1.90E-04 8.02E-05 4.46E-04 4.26E-05 1 117.53 132.99 1.00 

Formaldehyde A3-v0 1.71E-01 9.23E-02 3.42E-01 7.76E-02 1 87.01 98.46 1.00 

Hydrogen Sulfide A3-v0 1.65E-01 1.64E-01 1.72E-01 1.59E-01 1 4.20 4.76 0.00 

Indeno(1,2,3-cd)pyrene C3-v0 9.83E-06 1.06E-05 1.18E-05 7.10E-06 1 24.76 28.02 0.00 

Manganese A3-v0 3.49E-03 2.36E-03 6.79E-03 1.32E-03 1 83.26 94.21 1.00 

Mercury A3-v0 4.63E-03 4.01E-03 8.27E-03 2.55E-03 2 51.31 41.05 1.00 

Naphthalene C3-v0 4.02E-02 3.98E-02 4.30E-02 3.79E-02 1 6.36 7.20 1.00 

Nickel C3-v0 8.18E-03 6.79E-03 1.43E-02 3.40E-03 1 68.51 77.52 1.00 

Phenanthrene C3-v0 6.85E-04 5.53E-04 9.72E-04 5.30E-04 1 36.34 41.12 1.00 

Phenol C3-v0 1.53E-02 1.58E-02 1.59E-02 1.43E-02 1 5.81 6.57 0.00 

Pyrene C3-v0 1.28E-04 1.04E-04 2.29E-04 5.21E-05 1 71.00 80.34 1.00 

Toluene E3-v0 1.79E-01 1.78E-01 1.87E-01 1.72E-01 1 4.37 4.94 0.00 

Xylene (Total) E3-v0 4.13E-01 4.14E-01 4.15E-01 4.11E-01 1 0.50 0.56 0.00 

Zinc A3-v0 1.65E-02 1.56E-02 1.93E-02 1.45E-02 1 15.37 17.39 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-60 

Table D-25b. Summary of Data for Emission Factor Development – Gas Turbines with 

Duct Burners Firing Natural Gas and Refinery Fuel Gas Controlled with 

Selective Catalytic Reduction and Carbon Monoxide Oxidation Catalyst 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acenaphthene C3-v0 2.21E-08 2.00E-08 3.55E-08 1.07E-08 1 56.84 64.32 1.00 

Acenaphthylene C3-v0 1.07E-08 1.20E-08 1.23E-08 7.93E-09 1 22.70 25.68 1.00 

Acetaldehyde A3-v0 4.11E-06 3.09E-06 6.18E-06 3.06E-06 1 43.68 49.43 1.00 

Anthracene C3-v0 2.48E-08 2.26E-08 3.41E-08 1.76E-08 1 34.03 38.51 1.00 

Benzene C3-v0 1.52E-04 1.54E-04 1.69E-04 1.32E-04 2 11.10 8.88 0.00 

Benzo(a)anthracene C3-v1 1.49E-08 3.23E-09 3.86E-08 2.81E-09 1 138.05 156.22 0.86 

Benzo(a)pyrene C3-v0 9.53E-09 9.78E-09 1.26E-08 6.17E-09 1 34.09 38.57 0.00 

Benzo(b)fluoranthene C3-v0 2.50E-08 2.96E-08 3.20E-08 1.35E-08 1 40.14 45.42 0.82 

Benzo(g,h,i)perylene C3-v0 1.91E-08 1.86E-08 2.52E-08 1.35E-08 1 30.62 34.65 0.00 

Benzo(k)fluoranthene C3-v0 1.25E-08 1.13E-08 1.86E-08 7.49E-09 1 45.53 51.52 0.00 

Cadmium C3-v0 1.94E-06 9.84E-07 3.87E-06 9.55E-07 1 86.47 97.85 0.67 

Chromium (Hex) C3-v0 6.95E-06 6.60E-06 1.39E-05 1.45E-06 2 83.59 66.88 0.00 

Chromium (Total) C3-v1 4.99E-05 3.15E-05 1.71E-04 1.43E-05 2 120.88 96.72 1.00 

Chrysene C3-v0 1.07E-07 6.37E-08 2.26E-07 3.23E-08 1 96.95 109.70 1.00 

Copper A3-v0 1.75E-06 1.84E-06 2.46E-06 9.65E-07 1 42.72 48.34 1.00 

Dibenz(a,h)anthracene C3-v0 6.60E-09 7.55E-09 7.99E-09 4.26E-09 1 30.92 34.99 0.00 

Fluoranthene C3-v0 9.90E-08 9.92E-08 1.46E-07 5.14E-08 1 48.01 54.33 1.00 

Fluorene C3-v1 1.76E-07 7.46E-08 4.15E-07 3.96E-08 1 117.53 132.99 1.00 

Formaldehyde A3-v0 1.54E-04 8.36E-05 3.09E-04 7.03E-05 1 86.98 98.42 1.00 

Hydrogen Sulfide A3-v0 1.50E-04 1.49E-04 1.56E-04 1.44E-04 1 4.30 4.86 0.00 

Indeno(1,2,3-cd)pyrene C3-v0 9.14E-09 9.85E-09 1.10E-08 6.61E-09 1 24.76 28.02 0.00 

Manganese A3-v0 3.25E-06 2.19E-06 6.32E-06 1.23E-06 1 83.26 94.21 1.00 

Mercury A3-v0 4.35E-06 3.73E-06 7.82E-06 2.37E-06 2 51.85 41.49 1.00 

Naphthalene C3-v0 3.74E-05 3.70E-05 3.99E-05 3.52E-05 1 6.36 7.20 1.00 

Nickel C3-v0 7.60E-06 6.32E-06 1.33E-05 3.16E-06 1 68.51 77.52 1.00 

Phenanthrene C3-v0 6.37E-07 5.14E-07 9.03E-07 4.93E-07 1 36.34 41.12 1.00 

Phenol C3-v0 1.43E-05 1.47E-05 1.48E-05 1.33E-05 1 5.81 6.57 0.00 

Pyrene C3-v0 1.19E-07 9.63E-08 2.13E-07 4.84E-08 1 71.00 80.34 1.00 

Toluene E3-v0 1.62E-04 1.61E-04 1.69E-04 1.55E-04 1 4.30 4.87 0.00 

Xylene (Total) E3-v0 3.74E-04 3.76E-04 3.76E-04 3.72E-04 1 0.55 0.63 0.00 

Zinc A3-v0 1.53E-05 1.45E-05 1.80E-05 1.35E-05 1 15.37 17.39 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-61 

Table D-26a. Summary of Data for Emission Factor Development – Gas Turbines with 

Duct Burners Firing Natural Gas, Refinery Fuel Gas, and Liquefied Petroleum Gas 

Controlled with Selective Catalytic Reduction and Carbon Monoxide Oxidation Catalyst 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Arsenic B3-v0 1.70E-02 1.71E-02 1.79E-02 1.61E-02 1 5.27 5.96 0.00 

Beryllium B3-v0 3.40E-03 3.43E-03 3.57E-03 3.21E-03 1 5.28 5.97 0.00 

Cadmium B3-v0 7.41E-03 6.85E-03 8.94E-03 6.44E-03 1 18.06 20.43 0.40 

Copper B3-v0 4.08E-02 1.88E-02 8.74E-02 1.61E-02 1 99.07 112.11 0.87 

Lead B3-v0 6.82E-02 6.85E-02 7.16E-02 6.44E-02 1 5.25 5.94 0.00 

Manganese B3-v0 1.75E-01 9.89E-02 3.71E-01 5.58E-02 1 97.56 110.40 1.00 

Nickel B3-v0 2.78E-01 9.70E-02 6.60E-01 7.79E-02 1 118.86 134.50 1.00 

Phenol C3-v1 5.80E-02 2.31E-02 1.45E-01 5.55E-03 1 131.32 148.60 1.00 

Selenium B3-v0 1.70E-02 1.71E-02 1.79E-02 1.61E-02 1 5.27 5.96 0.00 

Zinc B3-v0 4.12E-01 4.08E-01 6.80E-01 1.47E-01 1 64.69 73.20 1.00 

Table D-26b. Summary of Data for Emission Factor Development – Gas Turbines with 

Duct Burners Firing Natural Gas, Refinery Fuel Gas, and Liquefied Petroleum Gas 

Controlled with Selective Catalytic Reduction and Carbon Monoxide Oxidation Catalyst 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Arsenic B3-v0 8.95E-06 9.00E-06 9.40E-06 8.46E-06 1 5.25 5.94 0.00 

Beryllium B3-v0 1.79E-06 1.80E-06 1.88E-06 1.69E-06 1 5.26 5.95 0.00 

Cadmium B3-v0 3.89E-06 3.60E-06 4.70E-06 3.39E-06 1 18.07 20.45 0.40 

Copper B3-v0 2.14E-05 9.89E-06 4.59E-05 8.46E-06 1 99.09 112.13 0.87 

Lead B3-v0 3.58E-05 3.60E-05 3.76E-05 3.39E-05 1 5.23 5.92 0.00 

Manganese B3-v0 9.21E-05 5.20E-05 1.95E-04 2.93E-05 1 97.60 110.45 1.00 

Nickel B3-v0 1.46E-04 5.09E-05 3.47E-04 4.09E-05 1 118.88 134.52 1.00 

Phenol C3-v1 3.05E-05 1.21E-05 7.65E-05 2.91E-06 1 131.46 148.76 1.00 

Selenium B3-v0 8.95E-06 9.00E-06 9.40E-06 8.46E-06 1 5.25 5.94 0.00 

Zinc B3-v0 2.16E-04 2.14E-04 3.58E-04 7.75E-05 1 64.70 73.22 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-62 

Table D-27a. Summary of Data for Emission Factor Development – Gas Turbines with No Duct 

Burners Firing Refinery Fuel Gas Controlled with Carbon Monoxide Oxidation Catalyst 

Substance 

CARB 

Rating 

Emission Factor (lb/MMcf) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acetaldehyde C3-v0 2.18E-02 2.22E-02 2.65E-02 1.67E-02 1 22.53 25.49 1.00 

Arsenic B3-v0 4.09E-03 4.15E-03 4.18E-03 3.95E-03 1 3.09 3.49 0.00 

Benzene C3-v0 1.49E-01 1.51E-01 1.53E-01 1.44E-01 1 3.34 3.78 0.00 

Beryllium B3-v0 2.05E-03 2.08E-03 2.08E-03 1.98E-03 1 2.78 3.14 0.00 

Cadmium B3-v0 7.41E-03 5.21E-03 1.29E-02 4.15E-03 1 64.24 72.70 1.00 

Chromium (Hex) C3-v0 2.04E-03 2.04E-03 2.05E-03 2.02E-03 1 0.70 0.79 0.00 

Chromium (Total) C3-v0 1.84E-02 1.01E-02 3.93E-02 5.93E-03 1 98.65 111.63 0.82 

Copper B3-v0 5.78E-02 5.49E-02 9.72E-02 2.12E-02 1 65.90 74.57 1.00 

Formaldehyde C3-v0 8.41E-01 8.36E-01 8.90E-01 7.97E-01 1 5.57 6.31 1.00 

Hydrogen Sulfide A3-v0 1.63E-01 1.64E-01 1.67E-01 1.58E-01 1 3.06 3.46 0.00 

Lead B3-v0 3.99E-02 4.15E-02 4.18E-02 3.64E-02 1 7.62 8.62 0.30 

Manganese B3-v0 1.80E-01 1.45E-01 3.40E-01 5.55E-02 1 80.76 91.39 1.00 

Mercury A3-v0 2.15E-02 1.55E-02 3.63E-02 1.27E-02 1 59.94 67.83 1.00 

Nickel B3-v0 2.33E-01 2.64E-01 2.86E-01 1.48E-01 1 31.93 36.13 1.00 

Phenol C3-v0 9.41E-03 5.99E-03 1.72E-02 5.07E-03 1 71.54 80.95 1.00 

Selenium B3-v0 5.42E-03 4.18E-03 7.93E-03 4.15E-03 1 40.11 45.39 0.00 

Toluene E3-v1 1.09E+00 4.34E-01 2.58E+00 2.56E-01 1 118.63 134.23 1.00 

Xylene (Total) E3-v1 3.14E+00 3.39E-01 8.85E+00 2.33E-01 1 157.44 178.16 1.00 

Zinc B3-v0 6.99E+00 8.23E+00 9.17E+00 3.56E+00 1 42.95 48.60 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-63 

Table D-27b. Summary of Data for Emission Factor Development – Gas Turbines with No Duct 

Burners Firing Refinery Fuel Gas Controlled with Carbon Monoxide Oxidation Catalyst 

Substance 

CARB 

Rating 

Emission Factor (lb/MMBtu) 

Tests RSD, % 

Uncertainty, 

% 

Detect 

Mean Median Maximum Minimum Ratio 

Acetaldehyde C3-v0 1.56E-05 1.58E-05 1.89E-05 1.19E-05 1 22.53 25.49 1.00 

Arsenic B3-v0 2.92E-06 2.96E-06 2.98E-06 2.81E-06 1 3.09 3.49 0.00 

Benzene C3-v0 1.06E-04 1.07E-04 1.09E-04 1.02E-04 1 3.34 3.78 0.00 

Beryllium B3-v0 1.46E-06 1.48E-06 1.49E-06 1.41E-06 1 2.78 3.14 0.00 

Cadmium B3-v0 5.28E-06 3.71E-06 9.18E-06 2.96E-06 1 64.24 72.70 1.00 

Chromium (Hex) C3-v0 1.45E-06 1.45E-06 1.46E-06 1.44E-06 1 0.70 0.79 0.00 

Chromium (Total) C3-v0 1.31E-05 7.19E-06 2.80E-05 4.23E-06 1 98.65 111.63 0.82 

Copper B3-v0 4.12E-05 3.91E-05 6.93E-05 1.51E-05 1 65.90 74.57 1.00 

Formaldehyde C3-v0 5.99E-04 5.96E-04 6.34E-04 5.68E-04 1 5.57 6.31 1.00 

Hydrogen Sulfide A3-v0 1.16E-04 1.17E-04 1.19E-04 1.12E-04 1 3.06 3.46 0.00 

Lead B3-v0 2.84E-05 2.96E-05 2.98E-05 2.59E-05 1 7.62 8.62 0.30 

Manganese B3-v0 1.29E-04 1.03E-04 2.43E-04 3.96E-05 1 80.76 91.39 1.00 

Mercury A3-v0 1.53E-05 1.11E-05 2.59E-05 9.05E-06 1 59.94 67.83 1.00 

Nickel B3-v0 1.66E-04 1.88E-04 2.04E-04 1.05E-04 1 31.93 36.13 1.00 

Phenol C3-v0 6.71E-06 4.27E-06 1.22E-05 3.62E-06 1 71.54 80.95 1.00 

Selenium B3-v0 3.86E-06 2.98E-06 5.65E-06 2.96E-06 1 40.11 45.39 0.00 

Toluene E3-v1 7.77E-04 3.10E-04 1.84E-03 1.83E-04 1 118.63 134.23 1.00 

Xylene (Total) E3-v1 2.24E-03 2.42E-04 6.31E-03 1.66E-04 1 157.44 178.16 1.00 

Zinc B3-v0 4.98E-03 5.87E-03 6.54E-03 2.54E-03 1 42.95 48.60 1.00 
Version 2.1.1 

Final ICR Version – Corrected Appendix D—Emission Factors for Combustion Sources 

D-64 

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