TECHNICAL SUPPORT DOCUMENT 

FOR EMISSIONS FROM 

PRODUCTION OF FLUORINATED GASES: 

FINAL RULE FOR MANDATORY REPORTING OF 

GREENHOUSE GASES 

Office of Air and Radiation 

U.S. Environmental Protection Agency 

November 5, 2010 
Table of Contents 

1. Source Description .....................................................................................................................1

A. Facilities Subject to the Rule ...............................................................................................1

B. How Fluorinated GHGs are Generated and Released at Fluorinated Gas Production 

Facilities ...............................................................................................................................1

C. Background on Uses of Fluorinated Gases ..........................................................................2

D. Potential Overlap Emission Points for Production and Suppliers. ......................................3

E. Total U.S. Production and Associated Emissions ................................................................4

2. Options for Reporting Threshold ...............................................................................................5

A. Uncontrolled Emissions Threshold ......................................................................................6

B. Controlled Emissions Threshold ..........................................................................................6

C. No Emissions Threshold (i.e., All-in) ..................................................................................7

3. Monitoring Methods, Data Collection and Current Plant Practices ..........................................7

A. Scoping speciation and Options for Characterizing Emitted Streams .................................8

i. Reliance on previous bench- and pilot-scale testing ......................................................8

ii. Initial Scoping speciation (including discussion of analytical methods) .......................8

B. Options for Developing Emissions Estimates ....................................................................10

i. Default Emission Factor ..............................................................................................10

ii. Mass Balance ...............................................................................................................11

1. Error Limits ............................................................................................................12

2. Mass Balance Approach Equations. ......................................................................15

3. Choice of Reactant Whose Yield Is Measured. ..... Error! Bookmark not defined.

4. Frequency of Measurement and Calculation. ........................................................23

5. Reactant and Byproduct Emissions. ......................................................................25

6. Alternative approach based on measurements of balanced elementError! Bookmark not defined

7. Current Plant Practices for Mass Balance ..............................................................26

iii. Monitoring of Process Vents .......................................................................................27

1. Process-Vent-Specific Emission Factor Approach. ...............................................27

2. Process-Vent-Specific Emission Calculation Factor Approach. ...........................32

3. Obtaining and Maintaining Representative Emission Factors ...............................35

4. Updates to emission factors and emission calculation factors. ..............................39

5. Potential Process Vent Emission Threshold. .........................................................39

6. Process Vent Preliminary Emission Estimates. .....................................................41

7. Current Plant Practices for Process Vent Monitoring ............................................41

8. Potential use of continuous emissions monitors to measure emissions from 

vents. ......................................................................................................................43

9. Equipment Leak Emissions Estimates. ..................................................................43

10. Destruction Efficiency Testing ..............................................................................45

C. Other Potentially Significant Emission Points ...................................................................50

4. Procedures for Estimating Missing Data .................................................................................51

5. QA/QC Requirements ..............................................................................................................52

6. Reporting and Recordkeeping Procedures ...............................................................................52

7. References ................................................................................................................................54 

i 
1. Source Description 

A. Facilities Subject to the Rule 

This source category, fluorinated gas production, covers emissions of fluorinated 

greenhouse gases (GHGs) that occur during the production of fluorinated gases. It also covers 

emissions of fluorinated GHGs that occur during transformation of fluorinated gases, destruction 

of fluorinated GHGs, and venting of residual fluorinated GHGs from returned containers when 

those processes are co-located with fluorinated gas production processes. Fluorinated GHGs 

include hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6), 

nitrogen trifluoride (NF3), and other fluorinated GHGs such as fluorinated ethers. Fluorinated 

gases include fluorinated GHGs, chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons 

(HCFCs). However, the source category excludes generation and emissions of HFC-23 during 

the production of HCFC-22, which is covered by subpart O of part 98 of the Mandatory 

Reporting Rule. 

Producing a fluorinated gas includes the manufacture of a fluorinated GHG, CFC, or 

HCFC from any raw material or feedstock chemical. This includes the manufacture of 

fluorinated gases for use in a process that will result in their transformation either at or outside of 

the production facility, including manufacture of a CFC or HCFC as an isolated intermediate for 

use in a process that will result in the transformation of the CFC or HCFC either at or outside of 

the production facility. Producing a fluorinated gas does not include the reuse or recycling of a 

fluorinated gas, the creation of HFC-23 during the production of HCFC-22, the creation of 

intermediates that are created and transformed in a single process with no storage of the 

intermediates, or the creation of fluorinated GHGs that are released or destroyed at the 

production facility. 

B. How Fluorinated GHGs are Generated and Released at Fluorinated Gas 

Production Facilities 

Fluorinated GHGs can be generated and emitted from production, transformation, 

destruction, and other processes at production facilities in a number of ways. Emissions from 

fluorinated gas production include fluorinated GHG products that are emitted upstream of the 

production measurement and fluorinated GHG by-products that are generated and emitted either 

without or despite recapture or destruction. Emissions from fluorinated gas transformation 

include emissions of fluorinated GHG feedstocks and possibly by-products of the transformation 

process. Emissions from fluorinated GHG destruction include fluorinated GHGs that survive the 

destruction process (or that are created as products-of-incomplete-combustion (PICs) from 

destruction). Other emissions sources are discussed further below. 

Many reactions producing fluorinated GHGs, CFCs, and HCFCs also generate significant 

quantities of chemically related by-products, e.g., through over-fluorination or side reactions. 

Table 1 provides an overview of some commonly produced fluorinated GHGs, CFCs, and 

HCFCs and their known fluorinated GHG by-products. Note that production of CFCs and 

HCFCs can generate and emit fluorinated GHGs such as various HFCs and some PFCs. These 

fluorinated GHG by-products occur due to the chemical similarities between HFCs, PFCs, 

HCFCs, and CFCs and the common use of halogen replacement chemistry to produce them. 

Also note that Table 1 is not exhaustive. It omits the most commonly known product and 

byproduct, HCFC-22 and HFC-23, which are covered by subpart O of the Mandatory Reporting 

1 
Rule. In addition, it does not include all of the by-products and products that have been 

identified by fluorinated gas producers. 

Table 1. Some Fluorinated Products and their By-products 

Product By-product(s) Source of information 

HFC-134a HFC-143a Italy National Inventory Report, 2009 

SF6 CF4 Italy National Inventory Report, 2009 

Electrochemical 

fluorination plant 

that produces a 

broad range of 

fluorochemical 

products, mainly 

for electronics 

industry 

SF6, CF4, 

C2F6, C3F8, 

C4F10, C5F12, 

C6F14, CF3SF5, 

C7F16, C8F18 

and C8F16O 

Belgium National Inventory Report, 2009 

http://unfccc.int/files/national_reports/annex_i_ghg_inventories/national_inven

tories_submissions/application/zip/bel_2009_nir_15apr.zip

CFC-11, CFC-12 CF4 2006 IPCC Guidelines 

CFC-115 C2F6 Italy National Inventory Report, 2009 

http://unfccc.int/files/national_reports/annex_i_ghg_inventories/national_inven

tories_submissions/application/zip/ita_2009_nir_15apr.zip

Trifluoroacetic acid 

(TFA) 

CF4, HFC-125 French National Inventory Report, 2009 

http://unfccc.int/files/national_reports/annex_i_ghg_inventories/national_inven

tories_submissions/application/zip/fra_2009_nir_7apr.zip

The quantities of by-products generated, as a share of the product, depend on the product 

and the process. Based on conversations with fluorinated gas producers, by-product generation 

rates generally range between one and five percent but can sometimes be higher or lower. 

Emissions of products, by-products, and feedstocks may occur from process vents, from 

equipment leaks from flanges, connectors, and other equipment pieces in the production line, 

from storage tanks storing either raw materials or products, from wastewater streams, from 

control devices (e.g., thermal oxidizers), and during the filling of tanker trucks, railcars, 

cylinders, or other containers that are distributed by the producer. Undesired by-products may be 

deliberately vented, and some product (or reactant) may be vented at the same time due to 

imperfect separation of by-products, products, and reactants. Emissions can also occur during 

scheduled maintenance and occasional service work on production equipment, during the 

blending and recycling of fluorinated GHGs, and during the evacuation of residual fluorinated 

GHGs from containers used to distribute products. EPA estimates that total emissions from this 

source category were approximately 10.6 million metric tons CO2e (mt CO2e) in 2006.1,2

C. Background on Uses of Fluorinated Gases 

Fluorinated gases are man-made gases used in several sectors. As noted above, they 

include fluorinated GHGs (HFCs, PFCs, SF6, NF3, and a number of fluorinated ethers), CFCs, 

and HCFCs, all of which are manufactured through various chemical processes. 

 

1

 Fluorinated GHG production data were from 2006; CFC and HCFC production data were from 2008. 

2 Memorandum from Schaffner, K. and Hancy, C., RTI International, to Ottinger, D., EPA/OAR/CCD. Threshold 

Analysis for Emissions, Promulgation of 40 CFR Part 98, subpart L, Fluorinated Greenhouse Gas Production. 

November 4, 2010. 

2 
Hydrofluorocarbons (HFCs) are the most commonly used fluorinated GHGs, used primarily to 

replace ozone-depleting substances in a number of applications, including air-conditioning and 

refrigeration, foams, solvents, and aerosols. PFCs are used in fire fighting and to manufacture 

semiconductors and other electronics. SF6 is used in a diverse array of applications, including 

electrical transmission and distribution equipment (as an electrical insulator and arc quencher) 

and in magnesium casting operations (as a cover gas to prevent oxidation of molten metal). 

Nitrogen trifluoride (NF3) is increasingly used in the semiconductor industry, to reduce overall 

semiconductor GHG emissions through processes such as NF3 remote cleaning and NF3

substitution during in-situ cleaning. Fluorinated ethers (HFEs and HCFEs) are used as 

anesthetics (e.g., isofluorane, desflurane, and sevoflurane) and as heat transfer fluids (e.g., the HGaldens). The manufacture of CFCs and HCFCs for emissive uses is being phased out under the 

Montreal Protocol, but production of these materials for use as feedstocks is permitted to 

continue indefinitely. As discussed further below, the volume of CFCs and HCFCs used as 

feedstocks in the U.S. is significant; even excepting HCFC-22, this volume is actually larger than 

the volume of fluorinated GHGs produced in the U.S. Fluorinated GHGs are powerful 

greenhouse gases whose ability to trap heat in the atmosphere is often thousands to tens of 

thousands of times greater than that of CO2, on a pound-for-pound basis. Some fluorinated 

GHGs are also very long lived; SF6 and the PFCs have lifetimes ranging from 3,200 to 50,000 

years.3

D. Potential Overlap Emission Points for Production and Suppliers. 

The facilities that are covered under the fluorinated gas production source category are 

many of the same facilities that are covered under the industrial gas supply source category. In 

general, the industrial gas supply source category is intended to cover or capture the quantities of 

fluorinated GHGs that are entering and leaving the U.S. supply of industrial gases, (i.e., amount 

of product), while the fluorinated gas production source category is intended to cover or capture 

the quantities of fluorinated GHGs emitted at fluorinated gas production facilities. Specifically, 

the industrial gas suppliers source category is meant to track the quantities of fluorinated GHGs 

that are (1) produced, (2) transformed, (3) destroyed, (4) imported, and (5) exported. The 

industrial gas suppliers source category would essentially track the amount of final product made 

(produced) at a production facility but not the emissions of fluorinated GHG from the production 

steps from raw material to final product. 

There are several areas of potential overlap between the emissions that are reported under 

the industrial gas suppliers source category and those that could be reported under the fluorinated 

gas production source category. The areas of overlap concern “downstream” emissions, meaning 

they occur at the fluorinated GHG production facility after the fluorinated GHG product 

measurement. Downstream emissions include those from container filling (if this occurs after 

the production measurement), fluorinated GHG transformation processes, destruction of 

fluorinated GHGs that are removed from the U.S. supply, recycling or reclamation of fluorinated 

GHGs, and evacuation of fluorinated GHG heels from returned cylinders or containers. 

(“Upstream” emissions occur at the fluorinated GHG production facility prior to the fluorinated 

GHG product measurement.) 

 

3 IPCC, 2006. 

3 
Fluorinated gas production facilities sometimes make a fluorinated GHG product that is 

later used as a raw material in making another product. For example, fluorinated GHG product is 

used as a raw material in transformation processes to produce fluoropolymers (the fluoropolymer 

product would not be considered a fluorinated GHG). Emissions of fluorinated GHGs that occur 

from transformation processes are an area of potential overlap, since the quantities produced for 

transformation may be reported under the industrial gas suppliers source category. 

Transformation processes may occur at the same site where fluorinated GHG products are 

produced, or they may occur at another fluorinated GHG production facility to which the 

fluorinated GHG feedstock is shipped. 

The emissions of fluorinated GHG from destruction processes used to remove fluorinated 

GHG from the U.S. supply is another area of overlap. The fluorinated GHG is returned to the 

facility and subtracted from the U.S. supply, however some emissions may occur from the 

destruction process, either as fugitives from the handling of the fluorinated GHG or as 

undestroyed emissions at the outlet of the destruction device. 

Filling cylinders or other containers (loading emissions) with fluorinated GHG product 

and blending of fluorinated GHG with other gases will most likely occur after the production 

measurement, classifying emissions for cylinder filling (loading) and blending as downstream 

processes. 

Recycling of used gas may be performed by the producers of new gas or by offsite 

recycling firms. Emissions may occur during handling and purification of old gas and during 

packaging of recycled gas.4 Since the used gas has already been counted as produced (used gas 

is removed from, and then added back into, the gas supply), recycling emissions are considered 

to be downstream of the production measurement. 

Evacuation of fluorinated GHG from returned cylinders or containers results in emissions 

that vary depending on process type and the composition and amount of the heel (residual gas) 

present. 

In theory, it might be possible to track emissions from transformation and destruction 

simply using quantities reported under 40 CFR part 98 subpart OO. However, this would require 

that (1) fluorinated GHGs that are produced only to be transformed or destroyed be tracked 

separately, (2) production, transformation, and destruction be measured to very good precision 

and accuracy (e.g., 0.2 percent), and (3) that no by-products be formed or emitted during these 

processes. If all of these conditions were met, emissions could be equated to the differences 

between production and transformation and production and destruction. In practice, however, it 

would be difficult to meet all of these conditions. 

E. Total U.S. Production and Associated Emissions 

The production of fluorinated gases includes production of fluorinated GHG (HFCs, 

PFCs, SF6, and NF3, HFEs), CFCs and HCFCs (except for HCFC-22 production processes). In 

2006 (some data are from 2003 and 2007), 12 U.S. facilities collectively produced over 350 

million mtCO2e (170,000 tons) of HFCs, PFCs, SF6, and NF3. EPA estimates that an additional 

 

4

 2006 IPCC, Chapter 3.10. 

4 
six facilities collectively produced 1 million mtCO2e of fluorinated anesthetics (HFEs) in 2005. 

The total U.S. production of CFCs and HCFCs (except HCFC-22) in 2008 was estimated to be 

approximately 266,000 tons. The majority of the CFC and HCFC production processes are colocated at facilities that also produce fluorinated GHGs. Another 2 facilities that produce CFC 

and HCFC products were identified that were not already included in the 12 facilities identified 

above for HFC, PFC, SF6, and NF3 production. Fluorinated gas production processes are 

sometimes co-located with fluorinated gas transformation processes or fluorinated GHG 

destruction processes. The total amounts of fluorinated gases transformed into other products or 

destroyed are not known. 

Fluorinated GHG emissions (actual emissions, following application of control 

techniques where applicable) from U.S. facilities producing fluorinated GHGs are estimated to 

range from 0.8 percent to 2 percent of the amount produced, depending on the facility. An 

emission rate of 1.5 percent is assumed for fluorinated GHG production processes. At an 

emission rate of 1.5 percent, the 12 fluorinated GHG facilities together are estimated to have 

emitted approximately 5.3 million mtCO2e of HFCs, PFCs, SF6, and NF3. The six additional 

HFE production facilities are estimated to have emitted approximately 17,000 mtCO2e of 

fluorinated anesthetics, using an emission rate of 1.5 percent. 

The quantity of emissions of fluorinated GHGs from production of CFCs and HCFCs is 

uncertain. However, the magnitude of by-product generation during F-GHG production (e.g., 

quantities equivalent to one to five percent of the mass of the product) suggests that significant 

quantities of by-product F-GHGs may be generated during production of chemically similar 

substances. Given the substantial amounts of CFCs and HCFCs that are produced in the U.S., 

emission rates could be relatively low and still result in significant emissions. In 2008, the 

combined tonnage of U.S. HCFC and CFC production was higher than that of all fluorinated 

GHG production in 2006 (the latest year for which data were available), with CFCs produced as 

feedstocks comprising the majority. (Although production of HCFCs and CFCs is limited under 

the regulations implementing Title VI of the CAA, production of these substances for use as 

feedstocks is permitted to continue indefinitely.) Assuming that this production resulted in 

emissions of fluorinated GHG by-products equal to one percent of the mass of CFCs and HCFCs 

produced,5 and that these byproducts had an average global warming potential (GWP) of 2000, 

emissions from CFC and HCFC production are estimated to have totaled 5.3 million mtCO2e in 

2008, the same as estimated emissions from fluorinated GHG production in 2006. (No estimate 

of fluorinated GHG emissions from transformation processes, or fluoropolymer production 

processes, is available.) These emissions, combined with those from fluorinated GHG 

production, lead to a total for the source category of 10.6 million mtCO2e. 

2. Options for Reporting Threshold 

EPA evaluated a range of threshold options for fluorinated gas production facilities. 

These included 1,000 mt CO2e, 10,000 mtCO2e, 25,000 mtCO2e, and 100,000 mtCO2e. 

Emission levels on both an uncontrolled and a controlled basis were evaluated. Because EPA 

 

5

The emission rate from CFC and HCFC production is assumed to be lower than that from fluorinated GHG 

production because only by-products are included in the former, while both products and by-products are included in 

the latter. 

5 
has little information on combustion-related emissions at fluorinated gas production facilities, 

these emissions were not included in the threshold analysis. 

A. Uncontrolled Emissions Threshold 

Facility-specific uncontrolled emissions (i.e., pre-control) were estimated for fluorinated 

GHG production processes (including fluorinated anesthetics production processes) by 

multiplying a factor of 3.0 percent by the estimated production at each facility. For CFC and 

HCFC production processes (except for HCFC-22 production processes), uncontrolled emissions 

were estimated by multiplying a factor of 2 percent by the estimated production at each facility. 

Uncontrolled emissions are strongly influenced by by-product generation rates, which are known 

to vary between zero and several percent for fluorinated gas production processes; thus, these 

estimates are uncertain. The results of the analysis for uncontrolled emissions from the 

production of HFCs, PFCs, SF6, NF3, CFCs, and HCFCs are shown in Table 2. (No emissions of 

fluorinated GHG from transformation processes, such as fluoropolymer production processes, 

are included in the analysis.) 

All or most production facilities would be covered by uncontrolled emission thresholds, 

i.e., 14 of 14 or 13 of 14 facilities would be covered depending on the cutoff level. Use of the 

uncontrolled emissions threshold would not allow for applying reductions from destruction 

devices, which may or may not be achieving the demonstrated destruction efficiency on a 

continuous operating basis. Under the uncontrolled emissions threshold option, emissions 

reductions would not be overstated and emissions to the atmosphere would not be understated. 

(It is uncertain where the emission levels of the individual anesthetic facilities would fall, and the 

anesthetic facilities and emissions are not included in Table 2. There are 6 anesthetic facilities 

that are estimated to generate a total of approximately 30,000 mt CO2e of emissions, by 

multiplying a factor of 3.0 percent by the estimated production.) Emissions from combustion 

sources at facilities are not included in the emissions estimate shown in Table 2. 

Table 2. Threshold Analysis for Fluorinated GHG Emissions from Production of HFCs, PFCs, SF6, 

NF3, CFCs, and HCFCs (Uncontrolled Emissions) 

Threshold 

Level 

(mt CO2e/r) 

Total National 

Emissions 

(mt CO2e) 

Number of 

Facilities 

Emissions Covered Facilities Covered 

mt CO2e Percent Number Percent 

1,000 10,600,000 14 10,600,000 100% 14 100% 

10,000 10,600,000 14 10,600,000 100% 14 100% 

25,000 10,600,000 14 10,600,000 100% 14 100% 

100,000 10,600,000 14 10,600,000 100% 13 93% 

B. Controlled Emissions Threshold 

Facility-specific controlled emissions (i.e., those following the control device, if in place) 

were estimated for fluorinated GHG production processes (including anesthetics production 

processes) by multiplying a factor of 1.5 percent by the estimated production at each facility. 

For CFC and HCFC production processes (except for HCFC-22 production processes), 

controlled emissions were estimated by multiplying by a factor of 1.0 percent by the estimated 

production at each facility. Controlled emissions were assumed to be half of uncontrolled 

6 
emissions at each facility. The results of the analysis for controlled emissions from the 

production of HFCs, PFCs, SF6, NF3, CFCs, and HCFCs are shown in Table 3. No emissions of 

fluorinated GHG from transformation processes (other than those that produce fluorinated 

GHGs) are included in the analysis. 

All or most of the production facilities would be covered by controlled emission 

thresholds, depending on the cutoff, although fewer facilities would be covered under the 

controlled emission threshold option (10 facilities) than under the uncontrolled emission 

threshold option (13 facilities) at the highest cutoff (i.e., 100,000 mtCO2e). Use of the controlled 

emissions threshold option would allow facilities to account for emission reductions achieved by 

destruction devices that had a demonstrated destruction efficiency. It is possible that emission 

levels may be understated using the controlled emissions option. (It is uncertain where the 

emission levels of the individual anesthetic facilities would fall, and the anesthetic facilities and 

emissions are not included in Table 3. There are 6 anesthetic facilities that are estimated to emit 

a total of approximately 15,000 mt CO2e of emissions, by multiplying a factor of 1.5 percent by 

the estimated production.) Emissions from combustion sources at facilities are not included in 

the emissions estimate shown in Table 3. 

Table 3. Threshold Analysis for Fluorinated GHG Emissions from Production of HFCs, PFCs, SF6, 

NF3, CFCs, and HCFCs (Controlled Emissions) 

Threshold 

Level 

(mt CO2e/r) 

Total 

National 

Emissions 

(mt CO2e) 

Number of 

Facilities 

Emissions Covered Facilities Covered 

mt CO2e Percent Number Percent 

1,000 10,600,000 14 10,600,000 100% 14 100% 

10,000 10,600,000 14 10,600,000 100% 14 100% 

25,000 10,600,000 14 10,600,000 100% 14 100% 

100,000 10,600,000 14 10,300,000 97% 10 71% 

C. No Emissions Threshold (i.e., All-in) 

Under an “all-in” approach, no emissions threshold level would be included in the rule 

and all facilities in the fluorinated gas source category, including facilities producing anesthetics, 

would be subject to the rule regardless of emission levels. The all-in approach would ensure that 

all facilities identified and quantified their fluorinated GHG emissions, even if they initially 

believed those emissions to be small. Some facilities that initially believed their emissions to be 

small could find that those emissions actually exceeded 25,000 mt CO2e (e.g., because a 

previously unidentified fluorinated GHG with a high GWP was being generated and emitted as a 

by-product). Facilities whose emissions remained below 25,000 mt CO2e or 15,000 mt CO2e 

could cease reporting after five or three years respectively. In addition, an all-in approach would 

provide an essentially level playing field because all facilities in the source category would be 

subject to the rule and be subject to the same economic impact from the reporting rule. 

However, an all-in approach would also increase the burden on facilities with uncontrolled 

emissions below 25,000 mt CO2e. This could result in higher reporting costs per metric ton CO2e 

for these facilities than for higher emitting facilities. 

3. Monitoring Methods, Data Collection and Current Plant Practices 

7 
A. Scoping Speciation and Options for Characterizing Emitted Streams 

i. Reliance on previous bench- and pilot-scale testing 

During research and development of a fluorinated gas product, companies develop 

laboratory, bench-scale, and pilot-scale processes to manufacture new products. During 

laboratory and bench-scale development of the process, companies generate small quantities of 

the product. The companies monitor and measure all aspects of the process, including rates and 

extent of reaction, reactant and full product and byproduct identity and compositions, and 

physical characteristics of the compounds. This testing and analysis of compounds in the various 

process streams generally identifies the product and all byproducts generated in the process. 

During these laboratory or bench-scale processes, process optimization is addressed by defining 

operating conditions that generate the best product yields and least byproducts, considering the 

most efficient use of resources. Following the laboratory and bench-scale level of process 

development, a process may be scaled to a larger basis, i.e., pilot-scale basis, to continue 

research and development of the process and to continue to refine process optimization. The 

pilot-scale process, meant to simulate a full-scale production process, generates a larger quantity 

of product than the laboratory scale process but less than a full-scale production process. The 

equipment used in pilot-scale processes is similar in design to what the full-scale process might 

be, and is used to continue research on the process, as the data available from earlier laboratory 

and bench-scale systems are applied. However, some data may not be directly applicable to the 

pilot-scale system. As part of the continued research, the company continues to test and analyze 

the products and byproducts from the pilot-scale process to confirm what compounds are 

generated in the process as operating conditions are refined (i.e., changed). 

The findings regarding the identities of the compounds generated during these stages of 

process research and development may be used to help understand the identities of the 

compounds present in emission and waste streams for the full-scale production process. The 

analyses are typically rigorous as the company is eager to know and learn as much as possible 

and limit side reactions and increase yields. A potential drawback to use of the laboratory and 

pilot scale compound and composition analyses is that there may be some differences in the 

products and byproducts as the process is scaled from laboratory/bench-scale to pilot-scale to 

full-scale production units. The earlier data may not be fully applicable to the larger scale 

processes. Differences are likely to occur between the laboratory and pilot-scales, and streams 

may need to be tested and analyzed again to detect changes between the pilot- and full-scale 

production processes. 

ii. Initial Scoping Speciation 

To ensure that all fluorinated GHGs that occur in emitted streams are accurately 

identified, an initial scoping speciation or test on vents and streams from fluorinated gas 

processes may be conducted. The initial scoping speciation would be conducted using methods 

that allow detection and identification of all compounds in the vent or stream. The identity of the 

specific compounds that are generated during the fluorinated gas production process is important 

to the emissions estimate. Some facilities have indicated that even with extensive laboratory and 

bench-scale compositional and quantitative analysis from research, development, and design 

stages of the process, unexpected F GHGs can be found in emissions streams.6 In some cases, 

 

6 Based on conversations with Fluorinated GHG producers, as referenced in section 7. 

8 
this may have occurred because the analytical methods used at the pilot- or laboratory-scale were 

not sensitive enough to detect fluorinated GHGs that occurred at low (but still higher than trace) 

concentrations; in other cases, it may have occurred because subtle differences between the 

laboratory- and full-scale processes led to the generation of new or different by-products. 

The results of the scoping speciation can be used to inform both the mass-balance and 

emission-factor approaches (described further below). In the mass balance approach, a total 

fluorine balance is conducted to account for all fluorine into the process (i.e., in the form of 

fluorine-containing reactants) and all fluorine out of the process (i.e., in the form of the fluorinecontaining product, and destroyed or recaptured fluorine-containing by-products, unconsumed 

reactants, or products). The difference, in terms of fluorine, is assumed to be emitted. The 

facility would determine what fraction of the total fluorine is emitted as the fluorine-containing 

reactant, by-products, or product by conducting emission characterizations for process vents by 

measurement to speciate the total fluorine. Because byproducts are created, knowledge of these 

informs the emissions estimate so that the byproduct compounds are appropriately represented in 

the emissions. For example, for facilities using the mass-balance approach, the scoping 

speciation can be used to determine whether some emissions are correctly assumed to occur in 

the form of the reactant, product, or by-products. For those facilities using an emissions factor 

approach, the results from the scoping speciation will ensure that emissions factors are 

appropriately developed for all byproduct compounds. The scoping speciation will identify 

byproducts that should be measured in subsequent emissions testing to develop emission factors. 

Note that some facilities may find it most convenient to conduct the initial scoping speciation, 

the emission measurements for mass balance emission characterization, and/or the emission 

testing for emission factor development at the same time). 

Accurately identifying the compounds emitted provides for a better fluorinated GHG 

emissions estimate and also a better CO2e emissions estimate because the appropriate GWPs are 

applied to the emitted compounds. If there is a difference between the GWPs of a product and a 

byproduct and if the emissions are assumed to consist exclusively of the product, the CO2e 

emissions could be overestimated or underestimated. Underestimation is a particular concern 

where the process unexpectedly generates a fluorinated GHG that is difficult to destroy (e.g., 

CF4). In this case, applying the destruction efficiency (DE) of the destruction device to the 

emissions may overestimate destruction and underestimate emissions. 

Facilities would conduct an initial scoping speciation on each fluorinated gas process at 

the facility that has at least one process vent over a threshold level.EPA evaluated emissions 

cutoffs on a process vent basis to be consistent with other approaches where emission cutoffs are 

also on a process vent basis. Only those processes with at least one process vent with fluorinated 

GHG emissions above a cutoff level would conduct the initial scoping speciation. We 

considered a limit based on CO2e on an uncontrolled basis for each process vent, and note that a 

cutoff based on fluorinated GHG, rather than CO2e, emissions may be appropriate because the 

identity and the GWP of some fluorinated GHG compounds may not be known. The fluorinated 

GHG emissions cutoff for process vents would be 1 metric ton fluorinated GHG. The estimate 

of emissions from each process vent could be determined using standard engineering 

calculations, previous measurements, and engineering assessments (i.e., similar to preliminary 

emission estimates discussed under process-vent-specific emissions calculation factors below). 

Because the specific fluorinated GHG byproducts may not be known, it may be appropriate to 

9 
apply the 1-metric-ton-fluorinated-GHG-emission cutoff to uncontrolled emissions. As noted 

above, the application of the destruction device’s DE may underestimate emissions (and 

therefore fail to trigger testing) if difficult-to-destroy fluorinated GHGs occur unexpectedly in 

the stream. 

A facility would not have to measure every stream or process vent to complete the initial 

scoping speciation. For each process with fluorinated GHG emissions above the cutoff level for 

process vents, facilities could select which process vents or streams to measure, focusing on 

those streams that are most likely to contain all of the fluorinated GHG (e.g., byproducts) 

anticipated to be generated or emitted. It is preferable that these fluorinated GHGs be at their 

maximum concentrations, although streams with smaller concentrations of byproducts may be 

tested if the scope and sensitivity of the analytical method allow detection of the compounds at 

lower concentration levels . 

Sampling and analytical methods capable of detecting and speciating fluorinated GHG 

compounds and capable of identifying multiple compounds simultaneously would be the best 

choices for the initial scoping speciation. For example, methods that use gas chromatography 

with mass spectrometry (GC/MS) are capable of detecting and identifying multiple fluorinated 

GHG compounds. Another example of an appropriate sampling and analytical method includes 

Fourier transform infrared (FTIR) analysis. There are several EPA reference methods and other 

consensus vetted methods that may be used to sample and analyze fluorinated GHG; these 

methods include EPA Method 18 - Measurement of Gaseous Organic Compound Emissions by 

Gas Chromatography (GC/ECD, GC/MS), EPA Test Method 320 Measurement of Vapor Phase 

Organic and Inorganic Emissions by Extractive Fourier Transform Infrared (FTIR) 

Spectroscopy, and ASTM D6348-03 (FTIR) Standard Test Method for Determination of 

Gaseous Compounds by Extractive Direct Interface Fourier Transform Infrared (FTIR) 

Spectroscopy. Each of these is briefly described below in the section on Process-Vent-Specific 

Emission Factor Approach. If speciation measurements are conducted at the stack, the facility 

would also conduct an EPA Method 1 series (Sample and Velocity Traverses for Stationary 

Sources), Method 2 series (Determination of Stack Gas Velocity and Volumetric Flow Rate), 

Method 3 series (Gas Analysis for Carbon Dioxide, Oxygen, Excess Air, and Dry Molecular 

Weight), and Method 4 (Determination of Moisture Content in Stack Gases). If a facility is not 

able to conduct EPA Method 2, alternative flow rate methods could be used, such as OTM 24 

(Tracer Gas Protocol For the Determination of Volumetric Flow Rate Through the Ring Pipe of 

the Xact Multi-Metals Monitoring System), or ALT-012 (Emission Measurement Center 

Approved Alternative Method). Other validated methods that are capable of detecting the 

analyte of interest at the concentration of interest could also be used. 

B. Options for Developing Emissions Estimates 

i. Default Emission Factor 

One option that was considered for characterizing fluorinated GHG is the use of default 

emission factors. These factors would provide a rough estimate of the quantity of fluorinated 

GHGs emitted. Although the default emission factor approach is simple and easily-implemented, 

it is also highly imprecise; emissions of fluorinated GHG products in U.S. plants are estimated to 

10 
vary from 0.8 percent to 2 percent of production, more than a factor of two (RTI, 2008).7

 Thus, 

applying a default factor (1.5 percent, for example) is likely to significantly overestimate 

emissions at some plants while significantly underestimating them at others. 

Under a somewhat more rigorous default emission factor approach, emission factors 

would be developed for similar types of emission points at multiple facilities within a source 

category. The emission factors for each type of emission point would be averaged to develop an 

industry-wide emission factor for that type of emission point. Because these EFs would represent 

average values over multiple facilities, some facilities would be above the EF and some would be 

below. As a result, such factors may not provide an accurate emissions determination for a 

single facility. Default EFs would not account for inter-facility variability that can occur due to 

the age of facility and equipment, equipment sizes, equipment design, differences in raw 

materials and suppliers, different typical operating parameters, and variations in the process 

operation that may not be readily apparent or known. In addition, default EFs would not provide 

information that EPA may need to compare the best and worst performers, or provide insights 

into which facilities have the most or fewest opportunities to obtain additional reductions. 

ii. Mass Balance 

In the total fluorine mass-balance approach, emissions are determined in terms of total 

fluorine8 rather than the fluorinated GHG product. Facilities determine the total fluorine emitted 

from the process by determining the total fluorine fed to the process, subtracting the total 

fluorine in the product resulting from the process, and subtracting the total fluorine that is 

destroyed or recaptured. Facilities would weigh or meter the reactants fed into the process, the 

product resulting from the process, and any streams that are destroyed and recaptured that 

contain reactants, byproducts, and product. Destroyed streams include those sent to the thermal 

oxidizer or other equipment, and recaptured streams may be sold, sent to another facility for 

destruction, or held for another purpose.9 Facilities calculate the total fluorine emitted as the 

difference in the total fluorine mass fed into the process, the total fluorine mass of the main 

product, and the total fluorine mass that is destroyed or recaptured.10 As discussed further 

below, it is EPA’s understanding that some facilities perform similar types of measurements and 

calculations to monitor their processes and yields. 

The difference is then assigned to loss of reactants, loss of product, and/or loss of 

byproducts. Facilities could assume that all the fluorine is emitted in the form of the fluorinated 

GHG that has the most significant GWP, or facilities could determine from measurements the 

 

7

 The emission rates cited were estimated for HCFC-22, which is an ozone-depleting substance and therefore 

excluded from the proposed rule. However, the production processes for many fluorinated GHGs are similar to 

those for HCFC-22 (2006 IPCC Guidelines, Volume 3, section 3.10.2.1), and therefore their emission rates are 

likely to be similar as well. 

8 Facilities could use another element as long as it occurred in all of the fluorinated GHGs fed into or generated by 

the process. 

9 Note that if these recaptured materials are fed back into the process, they must be counted at that time as fluorine 

additions to the process. 

10 The fluorine itself, of course, is not destroyed, but any fluorinated GHGs containing the fluorine are (to the 

destruction efficiency of the device). In the equations below, non-GHG fluorine-containing compounds that are 

removed from the process are treated as completely destroyed, since none of the fluorine in them is emitted as a 

fluorinated GHG. Fluorinated GHGs are assumed to be destroyed to the DE of the device for each fluorinated GHG. 

11 
fractions of the total fluorine emissions that consist of reactants, product, and byproducts. There 

may be only one reactant that contains fluorine, or if there are several reactants, the fluorine 

would be summed for the reactants. There may be processes with one by-product, or cases with 

several by-products, where the fluorine would be summed for all the by-products. There is likely 

one product. 

Because the mass-balance approach relies on the calculation of relatively small 

differences between relatively large numbers, measurements must have good precision to avoid 

large uncertainties in the emissions estimates. EPA evaluated methods to estimate and limit the 

error associated with the mass balance approach. 

1. Error Limits 

Precision and Accuracy Requirements for Individual Measurements 

One approach to limiting the error associated with emissions estimates developed using 

the mass-balance approach is to establish specific precision and accuracy requirements for each 

measurement used in the mass-balance equation. These measurements include mass 

measurements for reactants, products, and fluorinated GHG by-products, including feed streams, 

final product streams, emitted streams, and destroyed or recaptured streams. In addition, they 

include concentration measurements where products or by-products occur in streams with other 

substances. To limit the uncertainty of the emission estimate to ± 30 percent of the estimate, 

devices used to measure masses (e.g., flowmeters and scales) would need to be able to achieve 

precisions and accuracies near ± 0.2 percent or better, at least for streams with a large impact on 

the mass-balance calculation. Concentration measurements would need to be conducted with 

precisions and accuracies of ± 10 percent or better. This approach limits error and is 

straightforward to implement and enforce. However, it may require substantial expenditures to 

obtain accurate and precise measurements of quantities whose errors have little impact on the 

overall error of the emissions estimate. For example, under this approach, facilities might be 

required to upgrade flowmeters in streams that affect the emission estimate (and its uncertainty) 

only slightly. The approach also limits flexibility. Even a facility with a relatively large error in 

one stream may be able to bring the total error of its emissions estimate to a tolerable level by 

improving the accuracy and precision of other measurements that are used in the mass-balance 

equation, such as the mass flows of reactants and products. Thus, while this approach may be 

appropriate as an additional option for ensuring that emissions estimates are accurate and precise, 

it is probably not appropriate as the sole option. (See section 6 below for more discussion of this 

alternative approach.) 

Error Limit for the Emission Estimate as a Whole. 

Another approach to limiting the error of the mass-balance approach is to establish a limit 

on the error of the overall emission estimate. To estimate the statistical error associated with use 

of the mass-balance approach, facilities would be required to use error propagation, considering 

the accuracy and precision of their measurements and the calculation methods of the massbalance approach. Under this approach, EPA would not specify precision and accuracy 

requirements for individual mass or concentration measurements. Instead, EPA would require 

that the error associated with the overall estimate of fluorinated GHG emissions fall under a 

specific limit. This limit could be expressed in terms of a fraction of the emissions estimate 

12 
(relative error) or as a specific quantity (absolute error). Facilities could achieve this level of 

precision and accuracy however they chose. 

A maximum relative error of ± 30 percent would be comparable to that cited by a facility 

that has used an emission factor approach to estimate its fluorinated GHG emissions. It is also 

comparable to the error that EPA calculates for a facility with an emission rate of two percent 

and with good precisions and accuracies for its mass flow measurements (± 0.2 percent) and for 

its concentration measurement (± 10 percent) of a waste stream constituting five percent of the 

process’s fluorinated GHG output flow. For facilities whose emissions constitute a very small 

share of their inputs and outputs (e.g., one percent or less), a relative error of ± 30 percent would 

be very difficult to achieve using a mass-balance approach. At the same time, the absolute error 

of such a facility’s estimate may be smaller than the absolute error of a facility that meets the 

relative error test but that has a higher emission rate. It may therefore be appropriate to establish 

a maximum permissible absolute error of 3,000 mtCO2e for facilities whose estimates have 

relative errors greater than 30 percent. This absolute error is equivalent to 30 percent of the 

10,000 mtCO2e threshold that is used elsewhere in the subpart to establish requirements for 

different sources (e.g., process vents). Under this approach, processes whose emissions were 

lower than 10,000 mtCO2e could have relative errors higher than 30 percent so long as they met 

the limit on absolute error. This approach would avoid penalizing processes and facilities with 

low emissions. 

The absolute and relative errors associated with using the mass balance approach on a 

process may be estimated using Equations L-1, L-2, L-3, and L-4 in conjunction with either 

Equations L-7 through L-10 or Equation L-17. Alternatively, facilities may estimated these 

errors based on the variability of previous process measurements (e.g., the variability of 

measurements of stream concentrations), provided these measurements are representative of the 

current process and current measurement devices and techniques. Once errors have been 

calculated for the quantities in these equations, those errors would be used to calculate the errors 

in Equation L-6 and L-5. Where the measured quantity is a mass, the error in the mass would be 

equated to the accuracy or precision (whichever is larger) of the flowmeter, scale, or combination 

of volumetric and density measurements at the flowrate or mass measured. Where the measured 

quantity is a concentration, the error of the concentration would be equated to the accuracy or 

precision (whichever is larger) with which the concentration measurements estimate the mean 

concentration of that stream component, accounting for the variability of the process, the 

frequency of the measurements, and the accuracy or precision (whichever is larger) of the 

analytical technique used to measure the concentration at the concentration measured. If the 

variability of process measurements is used to estimate the error, this variability would be 

assumed to account both for the variability of the process and the precision of the analytical 

technique. Facilities may use standard statistical techniques such as the student’s t distribution to 

estimate the error of the concentration measurements as a function of process variability and 

frequency of measurement. 

Equation L-1 provides the general formula for calculating the absolute errors of sums and 

differences where the sum, S, is the summation of variables measured, a, b, c, etc. (e.g., S = a + b 

+ c): 

13 
( )( ) ( ) (Eq. L-1) 2

SA a b

*** c = [ ] + + ecebeae

2/1 2 2

Where: 

eSA = absolute error of the sum, expressed as one half of a 95 percent confidence interval. 

ea = relative error of a, expressed as one half of a 95 percent confidence interval. 

eb = relative error of b, expressed as one half of a 95 percent confidence interval. 

ec = relative error of c, expressed as one half of a 95 percent confidence interval. 

Equation L-2 provides the general formula for calculating the relative errors of sums and 

differences: 

( cba ) e SA

SR ++ = e (Eq. L-2) 

Where: 

eSR = relative error of the sum, expressed as one half of a 95 percent confidence interval. 

eSA = absolute error of the sum, expressed as one half of a 95 percent confidence interval. 

a+b+c = sum of the variables measured. 

Equation L-3 provides the general formula for calculating the absolute errors of products 

(e.g., flow rates of GHGs calculated as the product of the flow rate of the stream and the 

concentration of the GHG in the stream), where the product, P, is the result of multiplying the 

variables measured, a, b, c, etc. (e.g., P = a*b*c): 

( )( ) 2/1222

)

PA

**

cba = ++ eeecbae (Eq. L-3) 

Where: 

ePA = absolute error of the product, expressed as one half of a 95 percent confidence 

interval. 

ea = relative error of a, expressed as one half of a 95 percent confidence interval. 

eb = relative error of b, expressed as one half of a 95 percent confidence interval. 

ec = relative error of c, expressed as one half of a 95 percent confidence interval. 

Equation L-4 provides the general formula for calculating the relative errors of products: 

( cba

e

e PA

PR ** = (Eq. L-4) 

Where: 

ePR = relative error of the product, expressed as one half of a 95 percent confidence interval. 

ePA = absolute error of the product, expressed as one half of a 95 percent confidence 

interval. 

14 
a*b*c = product of the variables measured 

To estimate the annual CO2e emissions of the process for use in the error estimate, 

facilities would apply the mass-balance equations below to representative process measurements. 

If these process measurements represented less than one year of typical process activity, facilities 

would adjust the estimated emissions to account for one year of typical process activity. To 

estimate the terms FERd, FEP, and FEBk for use in the error estimate for Equations L-11, L-12, 

and L-13 of this section, facilities could use emission testing, monitoring of emitted streams, 

and/or engineering calculations or assessments, or in the alternative assume that all fluorine is 

emitted in the form of the fluorinated GHG that has the highest GWP among the fluorinated 

GHGs that occur in more than trace concentrations in the process. To convert the fluorinated 

GHG emissions to CO2e, facilities could use Equation A-1 of §98.2. For fluorinated GHGs 

whose GWPs are not listed in Table A-1 to subpart A of this part, facilities could use a default 

GWP of 2,000. 

2. Mass Balance Approach Equations. 

Estimating Fluorine Emissions 

The following set of equations summarizes the mass-balancing method for estimating 

fluorinated GHG emissions based on a total fluorine balance (another element could also be used 

in place of fluorine). 

The total mass of each fluorinated GHG emitted annually from each fluorinated gas 

production process and each fluorinated GHG transformation process would be estimated by 

using Equation L-5: 

∑( ) =

− − − = + +

p

EFGHGf ERp FGHGfEPp FGHGfE FGHGfBp

1

n

 (Eq. L-5) 

Where: 

EFGHGf = Total mass of each fluorinated GHG f emitted annually from production or 

transformation process i(metric tons). 

ERp-FGHGf = Total mass of fluorinated GHG reactant f emitted from production process 

i over the period p (metric tons, calculated in Equation L-11). 

EPp-FGHGf = Total mass of the fluorinated GHG product f emitted from production 

process i over the period p (metric tons, calculated in Equation L-12). 

EBp-FGHGf = Total mass of fluorinated GHG by-product f emitted from production 

process i over the period p (metric tons, calculated in Equation L-13). 

n = Number of concentration and flow measurement periods for the year. 

The total mass of fluorine emitted from process i over the period p would be estimated at 

least monthly by calculating the difference between the total mass of fluorine in the reactant(s) 

(or inputs, for processes that do not involve a chemical reaction) and the total mass of fluorine in 

15 
the product (or outputs, for processes that do not involve a chemical reaction), accounting for the 

total mass of fluorine in any destroyed or recaptured streams that contain reactants, products, or 

by-products (or inputs or outputs). An element other than fluorine may be used in the massbalance equation, provided the element occurs in all of the fluorinated GHGs fed into or 

generated by the process. In this case, the mass fractions of the element in the reactants, 

products, and by-products must be calculated as appropriate for that element. This calculation 

must be performed using Equation L-6: 

 (Eq. L-6) Rd DP

v

F ∑( d ) −∗−∗= FMFFPMFFRE

1

Where: 

EF = Total mass of fluorine emitted from process i over the period p (metric tons). 

Rd = Total mass of the fluorine-containing reactant d that is fed into process i over the 

period p (metric tons). 

P = Total mass of the fluorine-containing product produced by process i over the period p 

(metric tons). 

MFFRd = Mass fraction of fluorine in reactant d, calculated in Equation L-14. 

MFFP = Mass fraction of fluorine in the product, calculated in Equation L-15. 

FD = Total mass of fluorine in destroyed or recaptured streams from process i containing 

fluorine-containing reactants, products, and by-products, calculated in Equation L-7. 

v = Number of fluorine-containing reactants fed into process i. 

The mass of total fluorine in destroyed or recaptured streams containing fluorinecontaining reactants, products, and by-products would be estimated at least monthly using 

Equation L-7. In Equation L-7, the concentration of individual fluorinated GHGs present in each 

destroyed or recaptured stream (i.e., speciated approach) is measured and determined, and the 

amount of fluorine present is then calculated. (An alternative approach to determining the total 

fluorine in destroyed or recaptured streams, as shown using Equations L-17 and L-18, is 

discussed below in section 3.B.ii.3.) 

∑ ∑∑ ∑ ∑ ∑ (Eq. L-7) − −− − − − ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

+

⎥

⎥ ⎢ ⎦⎢

⎣ ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛ = + +

d j

dj Rd

k

Bk

j l

P kj kl

j

D j MFFPF MFFBB MFFR

1 11 1 1 1

* * *

q u ⎡ q x ⎤ v q

Where: 

FD = Total mass of fluorine in destroyed or recaptured streams from process i 

containing fluorine-containing reactants, products, and by-products over the 

period p. 

Pj = Mass of the fluorine-containing product removed from process i in stream j and 

destroyed over the period p (calculated in Equation L-8 or L-9). 

Bkj = Mass of fluorine-containing by-product k removed from process i in stream j 

and destroyed over the period p (calculated in Equation L-8 or L-9). 

16 
Bkl = Mass of fluorine-containing by-product k removed from process i in stream l 

and recaptured over the period p. 

Rdj = Mass of fluorine-containing reactant d removed from process i in stream j and 

destroyed over the period p (calculated in Equation L-8 or L-9). 

MFFRd = Mass fraction of fluorine in reactant d, calculated in Equation L-14. 

MFFP = Mass fraction of fluorine in the product, calculated in Equation L-15. 

MFFBk = Mass fraction of fluorine in by-product k, calculated in Equation L-16. 

q = Number of streams destroyed in process i. 

x = Number of streams recaptured in process i. 

u = Number of fluorine-containing by-products generated in process i. 

v = Number of fluorine-containing reactants fed into process i. 

The mass of each fluorinated GHG removed from process i in stream j and destroyed 

over the period p (i.e., Pj, Bkj, or Rdj, as applicable) would be estimated by applying the 

destruction efficiency of the device that has been demonstrated for the fluorinated GHG f to 

fluorinated GHG f using Equation L-8: 

M FGHGfj = FGHGf FGHGfj** ScDE j (Eq. L-8) 

Where: 

MFGHGfj = Mass of fluorinated GHG f removed from process i in stream j and destroyed 

over the period p. (This may be Pj, Bkj, or Rdj, as applicable.) 

DEFGHGf = Destruction efficiency of the device that has been demonstrated for fluorinated 

GHG f in stream j (fraction). 

cFGHGfj = Concentration (mass fraction) of fluorinated GHG f in stream j removed from 

process i and fed into the destruction device over the period p. If this 

concentration is only a trace concentration, cF-GHGfj is equal to zero. 

Sj = Mass removed in stream j from process i and fed into the destruction device over the 

period p (metric tons). 

The mass of each fluorine-containing compound that is not a fluorinated GHG and that is 

removed from process i in stream j and destroyed over the period p (i.e., Pj, Bkj, or Rdj, as 

applicable) would be estimated using Equation L-9: 

FCgj = FCgj

* ScM j (Eq. L-9) 

Where: 

MFCgj = Mass of non-fluorinated GHG fluorine-containing compound g removed from 

process i in stream j and destroyed over the period p. (This may be Pj, Bkj, or 

Rdj, as applicable). 

cFCgj = Concentration (mass fraction) of non-fluorinated GHG fluorine-containing 

compound g in stream j removed from process i and fed into the destruction 

device over the period p. If this concentration is only a trace concentration, 

cFCgj is equal to zero. 

17 
Sj = Mass removed in stream j from process i and fed into the destruction device over the 

period p (metric tons). 

The mass of fluorine-containing by-product k removed from process i in stream l and 

recaptured over the period p would be estimated using Equation L-10: 

= * ScB lBklkl (Eq. L-10) 

Where: 

Bkl = Mass of fluorine-containing by-product k removed from process i in stream l and 

recaptured over the period p (metric tons). 

cBkl = Concentration (mass fraction) of fluorine-containing by-product k in stream l 

removed from process i and recaptured over the period p. If this concentration is only 

a trace concentration, cBkl is equal to zero. 

Sl = Mass removed in stream l from process i and recaptured over the period p (metric 

tons). 

Attributing Fluorine Emissions to Reactants, Products, and By-Products (Characterizing 

Emissions) 

To estimate the terms FERd, FEP, and FEBk for Equations L-11, L-12, and L-13, 

facilities could assume that the total mass of fluorine emitted, EF, estimated in Equation L-6, 

occurs in the form of the fluorinated GHG that has the highest GWP among the fluorinated 

GHGs that occur in more than trace concentrations in the process unless facilities possess 

emission characterization measurements showing otherwise. The sum of the terms FERd, FEP, 

and FEBk would equal 1. Facilities would document the data and calculations that are used to 

speciate individual compounds and to estimate FERd, FEP, and FEBk. Facilities should exclude 

from calculations the fluorine included in FD, because this quantity has already been subtracted 

from emissions in Equation L-6. For example, they should exclude fluorine-containing 

compounds that are not fluorinated GHGs and that result from the destruction of fluorinated 

GHGs by any destruction devices (e.g., the mass of HF created by combustion of an HFC). 

However, they should include emissions of fluorinated GHGs that survive the destruction 

process. 

It may be appropriate scale emission characterization requirements to the size of the 

emissions from the process and process vent. For processes and process vents that have total 

emissions greater than a certain threshold, facilities would conduct measurements to determine 

what fraction of the emissions are each individual fluorinated GHG (FERd, FEP, and FEBk). For 

processes and process vents with emissions below the threshold, facilities could conduct 

measurements or rely on previous measurements. 

Facilities could estimate the total process emissions by relying on the estimate of total 

process emissions developed for the error estimate. To estimate emissions from process vents, 

facilities could conduct emission calculations or engineering assessments. For example, if the 

facility calculated that a process emitted 25,000 metric tons CO2e or more, the facility would 

then estimate the emissions from each process vent, considering controls, using engineering 

18 
calculations or engineering assessments. The facility would characterize by measurement any 

process vent that emits 25,000 metric tons CO2e or more and determine the fraction of each 

fluorinated GHG. 

For other vents, including vents from processes that emitted less than 25,000 metric tons 

CO2e, facilities would characterize emissions either by taking measurements or by using 

previous measurements on the process, bench-scale, or pilot-scale process to determine the 

fraction of each fluorinated GHG. 

If the emissions in either of the above cases were controlled and if the facility speciated 

the destroyed streams to estimate FD, the facility could use these monthly (or more frequent) 

measurements, along with the appropriate DEs of the destruction device, to characterize 

emissions after the destruction device. For vents that were uncontrolled or for which the facility 

quantified total fluorine, the facility would use previous or new measurements, as appropriate. 

If there was only one process vent associated with the process, the measurement would 

require only the fraction of each fluorinated GHG. When there is more than one process vent, 

the facility would have to include a flow rate for each process vent and develop a weighted 

average across the process for the fraction of each fluorinated GHG. The flow rates could be 

measured or estimated. For fluorine emissions that are not accounted for by vent estimates (i.e., 

fugitive emissions), facilities would apply the weighted average of the emission characterization 

from process vents to the emissions. 

The total mass of fluorine-containing reactant d emitted would be estimated at least 

monthly based on the total fluorine emitted and the fraction that consists of fluorine-containing 

reactants using Equation L-11. If the fluorine-containing reactant d is a non-GHG, facilities 

assume that FERd is zero. 

⎟

⎠

⎞ ⎜

⎝

⎛

+ +

=

∑ ∑ = =

− v

d

u

k

d Rd P k Bk

Fd

ipR

FER MFF MFFFEP FEB MFF

E

1 1

* * *

*EFER (Eq. L-11) 

Where: 

ER-ip = Total mass of fluorine-containing reactant d that is emitted from process i over the 

period p (metric tons). 

FERd = The fraction of the mass emitted that consists of the fluorine-containing reactant 

d. 

EF = Total mass of fluorine emissions from process i over the period p (metric tons), 

calculated in Equation L-6. 

FEP = The fraction of the mass emitted that consists of the fluorine-containing product. 

FEBk = The fraction of the mass emitted that consists of fluorine-containing by-product k. 

MFFRd = Mass fraction of fluorine in reactant d, calculated in Equation L-14. 

MFFP = Mass fraction of fluorine in the product, calculated in Equation L-15. 

MFFBk = Mass fraction of fluorine in by-product k, calculation in Equation L-16. 

19 
u = Number of fluorine-containing by-products generated in process i. 

v = Number of fluorine-containing reactants fed into process i. 

The total mass of fluorine-containing product emitted would be estimated at least 

monthly based on the total fluorine emitted and the fraction that consists of fluorine-containing 

products using Equation L-12. If the fluorine-containing product is a non-GHG, facilities may 

assume that FEP is zero. 

⎟

⎠

⎞ ⎜

⎝

⎛

∗+∗+∗

=

∑ ∑ = =

− v

d

u

k

d Rd P k Bk

F

ipP

FER MFF MFFFEP FEB MFF

E

1 1

* EFEP

 (Eq. L-12) 

Where: 

EP-ip = Total mass of fluorine-containing product emitted from process i over the period 

p (metric tons). 

FEP = The fraction of the mass emitted that consists of the fluorine-containing product. 

EF = Total mass of fluorine emissions from process i over the period p (metric tons), 

calculated in Equation L-6. 

FERd = The fraction of the mass emitted that consists of fluorine-containing reactant d. 

FEBk = The fraction of the mass emitted that consists of fluorine-containing by-product 

k. 

MFFRd = Mass fraction of fluorine in reactant d, calculated in Equation L-14. 

MFFP = Mass fraction of fluorine in the product, calculated in Equation L-15. 

MFFBk = Mass fraction of fluorine in by-product k, calculation in Equation L-16. 

u = Number of fluorine-containing by-products generated in process i. 

v = Number of fluorine-containing reactants fed into process i. 

The total mass of fluorine-containing by-product k emitted would be estimated at least 

monthly based on the total fluorine emitted and the fraction that consists of fluorine-containing 

by-products using Equation L-13. If fluorine-containing by-product k is a non-GHG, facilities 

may assume that FEBk is zero. 

⎟

⎠

⎞ ⎜

⎝

⎛

+ +

=

∑ ∑=

− u

k

Rd P k Bk

v

d

Fk

ipBk

FER MFF MFFFEP FEB MFF

EFEB E

1 1

* * *

* (Eq. L-13) 

Where: 

EBk-ip = Total mass of fluorine-containing by-product k emitted from process i over the 

period p (metric tons). 

FEBk = The fraction of the mass emitted that consists of fluorine-containing by-product 

k. 

FERd = The fraction of the mass emitted that consists of fluorine-containing reactant d. 

FEP = The fraction of the mass emitted that consists of the fluorine-containing product. 

EF = Total mass of fluorine emissions from process i over the period p (metric tons), 

calculated in Equation L-6. 

20 
MFFRd = Mass fraction of fluorine in reactant d, calculated in Equation L-14. 

MFFP = Mass fraction of fluorine in the product, calculated in Equation L-15. 

MFFBk = Mass fraction of fluorine in by-product k, calculation in Equation L-16. 

u = Number of fluorine-containing by-products generated in process i. 

v = Number of fluorine-containing reactants fed into process i. 

The mass fraction of fluorine in reactant d would be estimated using Equation L-14: 

Rd

F

Rd Rd MW

AW

MFF = MF * (Eq. L-14) 

Where: 

MFFRd = Mass fraction of fluorine in reactant d (fraction). 

MFRd = Moles fluorine per mole of reactant d. 

AWF = Atomic weight of fluorine. 

MWRd = Molecular weight of reactant d. 

The mass fraction of fluorine in the product would be estimated using Equation L-15: 

P

F

P P MW

AW

MFF = MF * (Eq. L-15) 

Where: 

MFFP = Mass fraction of fluorine in the product (fraction). 

MFP = Moles fluorine per mole of product. 

AWF = Atomic weight of fluorine. 

MWP = Molecular weight of the product produced. 

The mass fraction of fluorine in by-product k would be estimated using Equation L-16: 

Bk

F

Bk Bk MW

AW

MFF = MF * (Eq. L-16) 

Where: 

MFFBk = Mass fraction of fluorine in the product (fraction). 

MFBk = Moles fluorine per mole of by-product k. 

AWF = Atomic weight of fluorine. 

MWBk = Molecular weight of by-product k. 

3. Mass Balance Equations – Alternative Approach for Determining Total 

Fluorine in Destroyed and Recaptured Streams. 

As an alternative to the approach in Equation L-7 for determining the mass of total 

fluorine destroyed or recaptured, facilities could use the approach in Equation L-17. In Equation 

L-17, rather than determine the individual fluorinated GHGs present in each destroyed or 

recaptured stream (i.e., speciated approach) and then determine the amount of fluorine present 

21 
using Equation L-7, facilities may use a measurement technique on destroyed or recaptured 

streams that provides the total mass of fluorine (i.e., no speciation of individual fluorinated 

GHGs). This approach may be particularly useful for process with multiple byproducts. 

The total mass of fluorine in destroyed or recaptured streams containing fluorinecontaining compounds (including all fluorine-containing reactants, products, and by-products) 

would be estimated at least monthly using Equation L-17. 

∑ ∑ (Eq. L-17) = =

= +

x

l

lTFl

q

j

D avgj jTFj ScScDEF

1 1

** *

Where: 

FD = Total mass of fluorine in destroyed or recaptured streams from process i 

containing fluorine-containing reactants, products, and by-products. 

DEavgj = Weighted average destruction efficiency of the destruction device for the 

fluorine-containing compounds identified in destroyed stream j under 

§98.124(b)(4)(ii) and (5)(ii) (calculated in Equation L-18)(fraction). 

cTFj = Concentration (mass fraction) of total fluorine in stream j removed from process 

i and fed into the destruction device over the period p. If this concentration is 

only a trace concentration, cTFj is equal to zero. 

Sj = Mass removed in stream j from process i and fed into the destruction device 

over the period p (metric tons). 

cTFl = Concentration (mass fraction) of total fluorine in stream l removed from process 

i and recaptured over the period p. If this concentration is only a trace 

concentration, cBkl is equal to zero. 

Sl = Mass removed in stream l from process i and recaptured over the period p. 

q = Number of streams destroyed in process i. 

x = Number of streams recaptured in process i. 

The weighted average destruction efficiency that is applicable to a destroyed stream and 

that is used in Equation L-17 would be calculated using Equation L-18. Equation L-18 treats 

non-GHG fluorine-containing compounds as being completely destroyed, since none of the 

fluorine in them is emitted as a fluorinated GHG. Fluorinated GHGs are assumed to be 

destroyed to the DE of the device for each fluorinated GHG. 

∑ ∑

∑ ∑

= =

= =

+

+

= w

f

y

g

FGHGf j FGHGf jFCg g

y

g

jFCg g

w

f

FGHGf FGHGf j FGHGf

avgj

MFFSc MFFSc

MFFScDE MFFSc

DE

1 1

1 1

** **

*** **

 (Eq. L-18) 

Where: 

DEavgj = Weighted average destruction efficiency of the destruction device for the 

fluorine-containing compounds identified in destroyed stream j under 

§98.124(b)(4)(ii) or (b)(5)(ii), as appropriate. 

22 
DEFGHGf = Destruction efficiency of the device that has been demonstrated for fluorinated 

GHG f in stream j (fraction). 

cFGHGfj = Concentration (mass fraction) of fluorinated GHG f in stream j removed from 

process i and fed into the destruction device over the period p. If this 

concentration is only a trace concentration, cF-GHGfj is equal to zero. 

cFCgj = Concentration (mass fraction) of non-fluorinated GHG fluorine-containing 

compound g in stream j removed from process i and fed into the destruction 

device over the period p. If this concentration is only a trace concentration, 

cFCgj is equal to zero. 

Sj = Mass removed in stream j from process i and fed into the destruction device 

over the period p (metric tons). 

MFFFGHGf = Mass fraction of fluorine in fluorinated GHG f, calculated in Equation L-14, L15, or L-16, as appropriate. 

MFFFCg = Mass fraction of fluorine in non-fluorinated-GHG fluorinated compound g, 

calculated in Equation L-14, L-15, or L-16, as appropriate. 

w = Number of fluorinated GHGs in destroyed stream j. 

y = Number of non-fluorinated-GHG fluorine-containing compounds in destroyed 

stream j. 

4. Frequency of Measurement and Calculation. 

EPA considered several measurement and calculation frequencies for the mass balance 

approach. The total mass of each fluorinated GHG emitted from production processes could be 

estimated on a daily, weekly, or monthly basis by calculating the total fluorine in the reactants, 

subtracting the measured total fluorine in the product, and subtracting the measured total fluorine 

that is destroyed or recaptured. The daily measurement requires additional man hours to conduct 

more frequent measurements; however, in situations where input or output flows are estimated 

by multiplying concentrations by total mass flow rates of streams, and where one or both of these 

vary, frequent measurements will lead to more accurate and precise estimates than less frequent. 

A number of fluorocarbon producers have noted that daily measurements are burdensome 

and lead to large errors in the estimates of daily emissions. Many streams may contain acidic 

and reactive constituents such as HF, and sampling from these streams can create safety hazards. 

Daily product measurements can also vary significantly (sometimes exceeding 100 percent) for 

three reasons. First, when continuous processes are initially started, there is a lag time between 

the time the reactants are fed into the process and the time products emerge. Second, even after 

the process has been running for a while, the quantity of material in the process can vary based 

on changes in production rates and other conditions. Third, the relatively large errors in 

measurements of in-process product holding tanks (e.g., based on sight-glass readings) have a 

significant impact on daily mass balances. Over time, all of these effects smooth out, making 

longer term mass balances more reliable than daily mass balances.11 In view of these 

considerations, a requirement to perform measurements daily may not be justified, particularly 

for processes where concentrations show little variability. 

 

11 Note, however, that the sum of the daily mass-balances would also smooth out. 

23 
Because different processes operate with different ranges of process variability, it would 

be reasonable to require more frequent measurements for more variable processes. The 

appropriate frequency of measurement could be determined using the error calculation described 

above along with standard statistical techniques such as the Student’s t test. 

As discussed below in the context of emission testing, the more variable a parameter is, 

the more samples must be taken to precisely characterize the mean of that parameter. The 

number of samples required to estimate the mean of the parameter with a given level of 

confidence can be calculated based on the relative standard deviation (RSD) of the samples and 

on some assumptions about the distribution of the parameter. Where the set of samples is 

relatively small and only the sample standard deviation “s” is known (rather than the true 

standard deviation of the parameter), the appropriate statistic is often the Student’s t test. 

Monthly sampling will generate twelve concentration measurements per stream per year. 

If the variability among the concentration measurements is high enough that these 12 

measurements per year (i.e., monthly measurements) result in relative and absolute errors above 

the 30-percent and 3,000-mtCO2e limits, based on the Student’s t test, then the facility would 

need to increase the frequency of its measurements to meet the error limits. For example, 

facilities may find that weekly measurements are necessary to meet the error criteria for certain 

processes. By including process variability in the error calculation, facilities could make more 

frequent measurements if this were necessary to address process variability, but they would not 

need to incur the costs and risks of sampling for processes where less frequent measurements 

yielded precise results. 

Facilities that use the alternative to the error calculation (discussed further below) could 

make weekly measurements and calculations. EPA calculates that at a weekly frequency, these 

measurements will lead to reasonably accurate emission estimates (with an error near 30 percent) 

even if the concentrations in the process are highly variable (e.g., even if the RSD of the 

concentration measurements is 50 percent, which would be unusually high.) 

There are two other measurement practices that could address process variability. First, 

facilities could ensure that they made concentrations measurements that reflect the full range of 

conditions within the process, e.g., catalyst age. Facilities could also account for emissions that 

occur during process startups, shutdowns, and malfunctions, either recording fluorinated GHG 

emissions during these events or documenting that these events do not result in significant 

emissions. Together, these practices would limit the impact of sampling bias on emissions 

estimates. 

5. Alternative Precision and Accuracy Requirements 

An alternative to requiring facilities to perform the error calculation would be to specify 

conditions under which the error of the estimate would be expected to fall under the 3,000 

mtCO2e error limit. (The 3,000 mtCO2e absolute error was identified as the limit because it is 

consistent with the absolute error limit in the error calculation approach.) These conditions 

would include specific accuracy, precision, and frequency requirements for measurements and a 

process throughput limit. 

24 
To determine the appropriate requirements, one must consider the five factors that affect 

the absolute accuracy and precision of mass-balance estimates: (1) the relative accuracy and 

precision of the mass measurements, (2) the relative accuracy and precision of the methods used 

to measure concentrations (irrespective of process variability), (3) process variability, (4) the 

frequency of the measurements, and (5) the quantity of the fluorinated GHG throughput of the 

process, that is, the total masses of the fluorinated GHG reactants, products, and by-products fed 

into and generated by the process. A number of different combinations of measurement 

precisions, accuracies and frequencies would result in an emissions estimate with an acceptable 

absolute error; but some combinations are likely to be more easily achieved than others. Based 

on the research performed for this rule, one robust combination of requirements that is likely to 

be achievable for a number of processes is (1) to measure the masses identified in the rule with 

an accuracy and precision of ±0.2 percent of full scale or better, (2) to measure the 

concentrations identified in the rule using analytical methods with an accuracy and precision of 

±10 percent or better, (3) to conduct these measurements at least weekly, and (4) to limit the 

fluorinated GHG throughput of the process (including fluorinated GHG reactants, products, and 

by-products) to 500,000 mtCO2e or less. At an emission rate of two percent, the 500,000-

mtCO2e throughput limit would result in emissions of 10,000 mtCO2e. In combination with the 

precision, accuracy, and frequency requirements for measurements, this throughput would be 

expected to result in a maximum absolute error of 3,000 mtCO2e. 

Although some of the requirements could be relaxed and still result in an error near or 

below 3,000 mtCO2e, this would require a tightening of the other requirements. For example, if 

the requirements for the precision and accuracy of the mass measurements were relaxed to ±0.4 

percent, the requirements for the precision and accuracy of the concentration measurements 

would have to be tightened, e.g., to ±5 percent, and the frequency of these measurements would 

have to be increased. Comments received on the April 10, 2009 and April 12, 2010 proposed 

rules indicate that achieving precisions and accuracies of ±5 percent for concentration 

measurements, and conducting these measurements more often than weekly, could be quite 

challenging. The precision and accuracy requirements for concentrations and for the frequency 

of measurement are less stringent than those initially proposed in the April 10, 2009 rule; those 

for masses are the same as those initially proposed. 

Facilities that could not or chose not to meet these requirements would remain free to use 

the error calculation to demonstrate compliance with the mass-balance error limits. Under the 

error calculation, facilities have the flexibility to focus on improving the accuracy and precision 

of those measurements that have a significant impact on the overall error of the estimate rather 

than expending resources to improve the accuracy and precision of measurements that are not as 

important to the accuracy and precision of the emissions estimate. 

6. Comparison Between Proposed and Final Mass-Balance Approaches 

The version of the mass-balance approach adopted in the final rule is based on the same 

basic principle as the version that was proposed, but it also differs from the proposed version in 

some key respects. Both the proposed and final mass-balance approaches use the difference 

between the fluorine (or other element) fed into the process and the fluorine removed from the 

process to estimate the mass emitted. However, they differ in how they characterize the mass 

emitted. The proposed version of the mass-balance approach required calculation of the quantity 

25 
of by-product generated, which in turn required monitoring of any stream where by-products 

occurred in more than trace concentrations. Emissions of the by-product were assumed to equal 

the difference between the quantity of by-product generated and the quantity of by-product 

destroyed. Any remaining emissions were assumed to consist of the product. The final version 

of the mass-balance approach requires emission characterization measurements, which focus on 

the actual emissions from the process. 

The mass-balance approach in the final rule is fundamentally more flexible than that in 

the proposed rule. First, it allows for the possibility that emissions can consist of reactants as 

well as products and byproducts. Thus, the finalized version of the mass-balance approach is 

capable of quantifying emissions from transformation processes in which fluorinated GHGs are 

reactants as well as production processes in which fluorinated GHGs are products. Fluorinated 

GHG producers indicated in their comments that they would prefer a version of the mass-balance 

approach that was capable of quantifying emissions from transformation processes. 

Second, because emissions are characterized at the vent, the finalized mass-balance 

approach does not require facilities to speciate the flows in their streams. Instead, they are 

required to track the total fluorine in destroyed or recaptured streams. (While they may speciate 

these streams to do so, they may also use an analytical method that tracks total fluorine, such as 

ASTM D7359-08.) 

The facility must conduct emission characterization measurements, or use previous 

measurements, to develop the break out among the fluorinated GHG emitted. This emission 

measurement would focus on partitioning emissions among the various fluorinated GHGs (i.e., 

speciating the compounds). 

7. Current Plant Practices for Mass Balance 

A few facilities indicated that they conduct a form of the mass balance approach for 

determining fluorinated GHG emissions. Facilities noted overall that the difficulty of the mass 

balance approach depends on how sophisticated or complex the process is, i.e., how many input 

and output streams there are, and whether there are by-products generated and how many. 

Facilities that use a form of the mass balance approach indicated that it is often used in 

conjunction with an emissions factor based approach, to track yields and subtle or incremental 

changes in the process. These facilities conduct a “material balance” on the process, tracking the 

product yield, using the emission factor for some emission points, and the composition and 

concentration of the streams to determine if something in the process has changed. Generally, 

facilities have a good understanding of the chemistry for all processes and understand what raw 

materials are fed to the process, what side reactions occur, and what products and by-products 

are created. Facilities have laboratory-scale, pilot-plant, and full-scale stream analysis results. 

Facilities stated that with the original plant design, the mass balance equation is predicted. 

Facilities noted in particular that at the bench-scale phase of product and process development, 

they analyze every/all streams to identify all species and compounds. However, one facility 

indicated that while they do regularly measure byproduct concentrations in the product as a 

quality check, they do not regularly measure byproduct concentration across all process vents 

and streams. 

26 
Some facilities indicated that they conduct the mass balance on the fluorinated organic 

component only. 

Facilities noted, in particular, that they reconcile and calculate the production levels on a 

monthly basis rather than on shorter time frames such as daily or weekly. 

iii. Monitoring of Process Vents 

The emissions from process vents may be determined by a number of methods. These 

include emissions testing, engineering assessments, or calculations based on chemical 

engineering principles. All three methods may also be used to develop a site-specific emissions 

factor based on the emissions estimate and the process activity observed during the test or 

assumed for the calculations. These methods or approaches to determining emissions from 

fluorinated gas production processes provide emissions estimates of varying accuracy and 

precision. 

1. Process-Vent-Specific Emission Factor Approach. 

One method for estimating fluorinated GHG emissions is based on monitoring or 

estimating the composition and flow rate of the process vent streams along with the production 

activity parameter to develop a site-specific, process-vent-specific emission factor. Fluorinated 

gas producers have indicated that they develop and apply emission factors to estimate emissions 

from a range of processes. Typically a facility conducts an initial emissions test or engineering 

calculation to develop an emission factor or emissions calculation factor and updates the 

emissions factor as needed with process changes. Site-specific, process-vent-specific emission 

factors can be developed based on either measurement of process vent emissions or calculation 

of process vent emissions. The measurement of process vent emissions to develop an emissions 

factor is addressed in this section, and the calculation of process vent emissions is discussed 

below in Process-Vent-Specific Emission Calculation Factor approach. 

Under this approach, facilities would develop a process-vent-specific emission factor for 

each fluorinated GHG from each process vent by emissions testing. Facilities would use EPA, 

ASTM, industry-developed, and other testing methods, including consensus standards and 

industry-validated methods for determining the process emissions for emission factor 

development. The methods used would be quality-assured methods, capable of detecting the 

analyte of interest at the concentration of interest, and validated with the compound of interest at 

the concentration of interest. There are several EPA test methods available to sample and 

measure fluorinated GHG from processes in the fluorinated gas production source category, 

including EPA Method 320 (ASTM D6348-03) and EPA Method 18. Method 1 or 1A, Method 

2, 2A, 2B, 2C, or 2D, 2F, or 2G, Method 3, 3A, or 3B, and Method 4 must be conducted along 

with EPA Method 18. 

Method 320 and ASTM D6348-03. For Method 320, a gas sample is extracted through a 

heated gas transport and handling system and analyzed using FTIR spectroscopy to identify and 

quantify the gas stream components. It is applicable only for vapor phase analysis of organic or 

inorganic compounds. The sensitivity of this method can be adjusted based on the reference 

standards used to configure the FTIR, but also depends on the gas composition, moisture content, 

27 
and sampling losses. The ASTM D6348-03 FTIR method utilizes the same principles as Method 

320 but has some improved calibration requirements. 

Method 18. Method 18 utilizes gas chromatography (GC) and flame ionization, 

photoionization, electron capture, mass spectroscopy, or another applicable detection method to 

identify and quantify gaseous organic compounds. For the fluorinated GHG industry, electron 

capture and mass spectroscopy and possibly photoionization are the most appropriate detectors 

for identifying fluorinated GHG compounds. The identity and concentration levels are 

determined by comparison to known standards, which are used to calibrate the GC. Stack gas 

samples may be collected through direct interface sampling, dilution interface sampling, 

adsorption tube sampling, or bag sampling. One needs to consider whether significant temporal 

changes in flow rate and/or concentration occur in the process (e.g., batch processes) when 

selecting and applying the sampling approach for this method. The direct interface, dilution 

interface, and adsorption tube sampling are not designed for sources that vary in concentration. 

Instead, an integrated bag sample with proportional sampling (sample rate adjusted 

proportionally with changes in stack gas flow rate) would be appropriate for an emission source 

with a varying flow rate and concentration. If the direct interface method is used, the timeframe 

of temporal changes of concentration in relation to the analytical timeframe needs to be 

considered. For example, if significant changes in concentration are expected to occur rapidly 

(e.g., 10-minute time frame), but the GC analytical cycle is 30 minutes, a representative sample 

analysis may not be obtained; on the other hand, for this situation, if the analytical cycle is 5 

minutes, a representative sample would be obtained. Variations in vent gas flow rate also need 

to be considered; for example, if vent flow rates and concentration are varying with time and the 

direct interface method is being used, the vent flowrate should be continuously monitored so that 

the flowrate and concentration can be correlated to determine mass emissions. For any of the 

sampling methods, all samples must be analyzed within a few hours of collection. 

Method 320, ASTM D63248-03 and Method 18 also require that the flow rate be 

relatively constant during sampling. If the flow rate varies significantly over the course of the 

sampling, then this fluctuation must be accounted for when measuring concentration and 

calculating mass emissions. 

OTM 24, the Tracer Gas Protocol For the Determination of Volumetric Flow Rate 

Through the Ring Pipe of the Xact Multi-Metals Monitoring System (OTM 24) uses a GC 

equipped with an FID to measure the concentration at a specific point. A tracer gas is introduced 

into the process to perform a volumetric flow rate determination, which depends on the tracer 

flow rate, concentration at the measurement point and calibration and analysis data. 

The Emission Measurement Center Approved Alternative Method (ALT-012) is designed 

for measuring particulate emissions in situations where gas velocities are low and difficult to 

measure and subject to variations over time. ALT-012 can also be used to measure ducts and 

stacks that are not subject to stratification. First, locations are identified upstream, for injecting 

the tracer gas, and downstream, for the tracer gas measurement. For a complete measurement, 

three ten-minute long sampling intervals must be completed at the downstream location. 

Nuclear magnetic resonance (NMR) spectroscopy is a commonly used analytical 

technique in organic chemistry. Organic compounds are placed in a magnetic field and exposed 

28 
to electro-magnetic energy, usually in the form of radio frequency (RF), and the nuclei of certain 

atoms absorb the radiation, which causes the nuclear spin to realign in the higher energy 

direction. The wavelength the atom absorbs is dependent on the neighboring atoms in the 

compound, and the resulting spectrum is called the NMR spectrum. This is a complex laboratory 

analytical method used to determine the structure of molecules. Much like using infrared 

spectroscopy (IR) to identify functional groups, analysis of a NMR spectrum provides 

information on the number and type of chemical entities in a substance. Also, the dependence of 

the transition energy on the position of a particular atom in a molecule makes NMR spectroscopy 

extremely useful for determining the structure of molecules. 

Using the applicable method(s), process activity (e.g., production or feed) would be 

monitored at the same time as emissions; the emission factor would be developed by dividing the 

emissions by the activity. Both continuous and batch processes are used in the fluorinated gas 

production source category. Typically, for continuous processes, facilities would measure and 

determine the fluorinated GHG emission rate based on test runs of at least 1 hour duration. For 

continuous processes, facilities would use Equation L-19. 

1

60 *

10

1 * 1 ***

106 3 SV

E QMW PV

PV

ContPV = C (Eq. L-19) 

Where: 

EContPV = Mass of fluorinated GHG f emitted from process vent v from process i during the 

emission test during test run r (kg/hr). 

CPV = Concentration of fluorinated GHG f during test run r of the emission test (ppmv). 

MW = Molecular weight of fluorinated GHG f (g/g-mole). 

QPV = Flow rate of the process vent stream during test run r of the emission test (m3

/min). 

SV = Standard molar volume of gas (0.0240 m3

/g-mole at 68°F and 1 atm). 

1/103

 = Conversion factor (1 kilogram/1,000 grams). 

60/1 = Conversion factor (60 minutes/1 hour). 

To develop the site-specific, process-vent-specific emission factor, facilities would track 

the process activity during the emissions testing and combine it with the emissions. For 

continuous processes, a facility would divide the fluorinated GHG emissions during the test by 

the process activity during testing. Equation L-20 would be used to estimate the average 

emission factor. 

r

Activity

E

EF EmissionTest

PV

PV

∑ ⎟

⎟

⎠

⎞

⎜

⎜

⎝

⎛

= 1

r

 (Eq. L-20) 

Where: 

EFPV = Average emission factor for fluorinated GHG f emitted from process vent 

v during process i (e.g., kg emitted/kg activity). 

29 
EPV = Mass of fluorinated GHG f emitted from process vent v from process i 

during the emission test during test run r (kg emitted/hr for continuous). 

ActivityEmissionTest = Process feed, process production, or other process activity rate during the 

emission test during test run r (e.g., kg product/hr). 

r = Number of test runs performed during the emission test. 

Development of the emissions testing program requires testing during representative 

process operation. To develop a representative emission factor for the process vent, the facility 

should give some consideration to what process variability might be present in the process. For 

each operating scenario of the process, the emissions test data must be representative of the 

typical process operation while also including process variability.12 The full range of process 

operating conditions should be included. The typical process operation conditions would include 

yield, temperature, pressure, and flow rates. The operating conditions and the process activity 

should be measured during the emissions test. See section 3.B.iii.3 below for more information 

on representativeness. 

Emission factors may be developed on an uncontrolled or a controlled basis depending on 

the emission level of the process vent. Using the process-vent-specific emissions factor method, 

a facility would estimate emissions using the emission factor and would track process activity on 

an on-going basis. To estimate annual fluorinated GHG emissions from each vent, facilities 

would multiply each uncontrolled emission factor by the appropriate activity data and account 

for the use (and uptime) of destruction devices. Where controlled emission factors are 

developed, a facility would multiply each controlled emission factor by the appropriate activity 

data for periods when the process vent is vented to the destruction device. For periods when the 

process vent is not venting the destruction device (i.e., bypassing), the facility would develop an 

emission factor for these periods as well (i.e., an uncontrolled emission factor) or would develop 

an emission calculation factor. 

For facilities that conduct emissions testing on a controlled vent, the emissions of each 

fluorinated GHG for each process vent would be calculated using Equation L-21. 

PV = EFE −CPV

* ActivityC + ECF −UPV* ActivityU

 

 (Eq. L-21) 

Where: 

EPV = Mass of fluorinated GHG f emitted from process vent v from process i, 

for the year (kg). 

EFPV-C = Average emission factor for fluorinated GHG f emitted from process 

vent v during process i based on testing after the destruction device (kg 

emitted/activity)(e.g., kg emitted/kg product). 

ActivityC = Total process feed, process production, or other process activity during 

the year for which emissions are vented to the properly functioning 

destruction device (i.e., controlled). 

12 Operating scenarios and other issues associated with developing representative emission factors are discussed 

further below under “Obtaining and Maintaining Representative Emission Factors.” 

30 
ECFPV-U = Emission calculation factor for fluorinated GHG f emitted from process 

vent v during process i during periods when the process vent is not 

vented to the properly functioning destruction device (kg 

emitted/activity)(e.g., kg emitted/kg product). 

ActivityU = Total process feed, process production, or other process activity during 

the year for which the process vent is not vented to the properly 

functioning destruction device (e.g., kg product) 

For facilities that conduct emissions testing on an uncontrolled vent, the emissions would 

be calculated by applying the destruction efficiencies of the device that have been demonstrated 

for the fluorinated GHGs in the vent stream to the fluorinated GHG emissions for the process 

vent, using Equation L-22 of this section. Facilities would apply the destruction efficiency only 

to the portion of the process activity during which emissions are vented to the properly 

functioning destruction device (i.e., controlled). 

EFE (Activity Activity ( DE)) PV = −UPV*

U + C 1* − (Eq. L- 22) 

Where: 

EPV = Mass of fluorinated GHG f emitted from process vent v from process i, 

for the year, considering destruction efficiency (kg). 

EFPV-U = Emission factor (uncontrolled) for fluorinated GHG f emitted from 

process vent v during process i (kg emitted/kg product). 

ActivityU = Total process feed, process production, or other process activity during 

the year for which the process vent is not vented to the properly 

functioning destruction device (e.g., kg product). 

ActivityC = Total process feed, process production, or other process activity during 

the year for which the process vent is vented to the properly functioning 

destruction device (e.g., kg product). 

DE = Demonstrated destruction efficiency of the destruction device (weight 

fraction). 

When there is more than one operating scenario associated with a process, the emissions factor 

developed for the first operating scenario of the process may be adjusted for other operating 

scenarios depending of the magnitude of emissions. Facilities would use Equation L-23 to 

develop an adjusted process-vent-specific emission factor. 

PV

T

UT

PVadj EF

ECF

EF = * ECF (Eq. L-23) 

Where: 

31 
EFPVadj = Adjusted process-vent-specific emission factor for an untested operating scenario. 

ECFUT = Emission calculation factor for the untested operating scenario developed under 

paragraph (c)(4) of this section. 

ECFT = Emission calculation for the tested operating scenario developed under paragraph 

(c)(4) of this section. 

EFPV = Process-vent-specific emission factor for the tested operating scenario. 

 Facilities may sum the emissions of each fluorinated GHG from all of the process vents 

in a process for the year to estimate the total process vent emissions of each fluorinated GHG. 

Facilities would use Equation L-24. 

= ∑ (Eq. L-24) 

v

Pfi EE PV

1

Where: 

EPfi = Mass of fluorinated GHG f emitted from process vents for process i, for 

the year (kg). 

EPV = Mass of fluorinated GHG f emitted from process vent v from process i, for 

the year, considering destruction efficiency (kg). 

v = Number of process vents in process i. 

2. Process-Vent-Specific Emission Calculation Factor Approach. 

As mentioned above, another method for estimating fluorinated GHG emissions is based 

on use of engineering calculations to determine the composition and flow rate of the process vent 

streams. These emissions estimates are divided by the production activity parameter to develop 

a site-specific, process-vent-specific emission calculation factor. A variation of this method 

includes use of engineering assessments to develop process-vent-specific emission calculation 

factor. Facilities have indicated that they regularly use engineering calculations and engineering 

assessments to estimate fluorinated GHG emissions. 

Engineering calculations use chemical engineering principles and component property 

data to calculate emissions. Acceptable calculation methods for uncontrolled and controlled 

process vent emissions are included in a number of rule texts and EPA guidance documents. 

Other promulgated rule texts that contain appropriate calculation equations include the 

Miscellaneous Organic NESHAP (MON) NESHAP in §63.2460(b)(1) through (4) (the MON 

rule text also refers to equations in the Pharmaceutical NESHAP in §63.1257(d)(2)(i) for 

uncontrolled and §63.1257(d)(3)(i) for controlled emissions with some noted caveats to the 

calculations). These rule texts include process calculation methods and equations for vapor 

displacement, purging, heating, depressurization, vacuum systems, gas evolution, air drying, and 

32 
empty vessel purging. An even more recent guidance document that provides appropriate 

calculations for chemical manufacturing operations is the Methods for Estimating Air Emissions 

from Chemical Manufacturing Emissions, Volume II: Chapter 16, of the Emission Inventory 

Improvement Program. 

Engineering assessments may be conducted using previous emissions test data or other 

information available on the process. Facilities typically have component and composition data 

available from the original research and development activities on the process and from the 

process’ lifetime of operation. If the facility performed a scoping speciation as described in 

section 3.A.ii above, the results of that test should also be considered. For process vent 

emissions determinations, facilities could conduct an engineering assessment to calculate 

uncontrolled emissions for each process vent and for each emission episode. Various rules for 

other regulatory programs include use of engineering assessments to estimate emissions from 

processes and process vents. Other promulgated rules that allow use of engineering assessments 

include NESHAP rules in 40 CFR part 63, such as subpart GGG for Pharmaceutical 

Manufacturing in §63.1257(d)(2)(ii) and subpart FFFF for MON in §63.2460(b). Engineering 

assessments include use of previous emissions test data where the emissions are representative of 

current operating practices; bench-scale or pilot-scale streams analysis results for identifying 

stream components and composition for products, byproducts, and wastes; design analysis based 

on chemical engineering principles, measurable process parameters, or physical or chemical laws 

or properties. These previous emissions data, analysis, and calculations may be used to identify 

fluorinated GHG compounds and their concentrations in various streams. 

To develop the site-specific, process-vent-specific emissions calculation factor, facilities 

would first calculate the fluorinated GHG emissions and divide them by the appropriate process 

activity associated with the emissions calculation. Equation L-25 would be used to estimate the 

emission calculation factor. 

vepresentati

PV

PV Activity

ECF

Re

= E (Eq. L-25) 

Where: 

ECFPV = Emission calculation factor for fluorinated GHG f emitted from process 

vent v during process i (e.g., kg emitted/kg product). 

EPV = Average mass of fluorinated GHG f emitted, based on calculations, from 

process vent v from process i during the period or batch for which 

emissions were calculated, for either continuous or batch (kg emitted/hr 

for continuous, kg emitted/batch for batch). 

ActivityRepresentative = Process feed, process production, or other process activity rate 

corresponding to average mass of emissions based on calculations (e.g., kg 

product/hr for continuous, kg product/batch for batch). 

As with the process-vent-specific emissions factor, a facility would estimate emissions 

using the emissions calculation factor and would track process activity on an on-going basis. To 

estimate annual fluorinated GHG emissions from each vent, facilities would multiply each 

emission calculation factor by the appropriate activity data and account for the use (uptime, by33 
pass, and/or downtime) of destruction devices. Equation L-26 would be used to estimate 

emissions for each individual process vent if the process vent is not vented to a destruction 

device, and Equation L-27 would be used if the process vent is vented to a destruction device. 

ECFE * Activity PV = PV (Eq. L-26) 

Where: 

EPV = Mass of fluorinated GHG f emitted from process vent v from process i, for 

the year (kg). 

ECFPV = Emission calculation factor for fluorinated GHG f emitted from process 

vent v during process i (kg emitted/activity) (e.g., kg emitted/kg product). 

Activity = Process feed, process production, or other process activity during the year. 

ECFE (Activity Activity ( DE)) PV = PV*

U + C 1* − (Eq. L-27) 

Where: 

EPV = Mass of fluorinated GHG f emitted from process vent v from process i, for 

the year considering destruction efficiency (kg). 

ECFPV = Emission calculation factor for fluorinated GHG f emitted from process 

vent v during process i (e.g., kg emitted/kg product). 

ActivityU = Total process feed, process production, or other process activity during the 

year for which the process vent is not vented to the properly functioning 

destruction device (e.g., kg product). 

ActivityC = Total process feed, process production, or other process activity during the 

year for which the process vent is vented to the properly functioning 

destruction device (e.g., kg product). 

DE = Demonstrated destruction efficiency of the destruction device (weight 

fraction). 

The emissions of each fluorinated GHG from all process vents in the process would be 

summed to obtain the total emissions from process vents for the facility as a whole. Equation L28 would be used to sum fluorinated GHG emissions over all process vents for the process, and 

Equation L-29 would sum the emissions from all processes. Other emission points at the facility 

such as equipment leaks, storage tanks, or wastewater would have to be accounted for separately 

and added in to the facility total. 

= ∑ (Eq. L-28) Pfi EE PV

1

v

Where: 

34 
EPfi = Mass of fluorinated GHG f emitted from process vents for process i, for 

the year (kg). 

EPV = Mass of fluorinated GHG f emitted from process vent v from process i, for 

the year, considering destruction efficiency (kg). 

v = Number of process vents in process i. 

3. Obtaining and Maintaining Representative Emission Factors 

Process conditions 

Emission rates from a process depend on the operating conditions of that process. Thus, 

to ensure that emission factors are representative, facilities should define the operating scenario 

that encompasses the typical range of operating conditions for the process. If the process has 

multiple operating scenarios, the facility should develop a representative emissions factor for 

each operating scenario. To define the process operating scenario, a facility could include 

information on the process description, the specific process equipment used, and the range of 

operating conditions; the process vents, emission episodes and durations, and the quantity of 

uncontrolled fluorinated GHG emissions; the control device or destruction device used to control 

emissions; and the manifolding of process vents within the process and from other processes. 

Other operating scenarios should also be defined for differences in operating conditions that 

affect emissions. Examples of situations where process differences may warrant separate 

operating scenarios include the following: making small volumes of a product in one set of 

batch process equipment part of the year and making larger volumes in larger batch process 

equipment part of the year; use of two different types of catalyst in the same process; deliberate 

alterations in process conditions such as temperature or pressure to shift the reaction to a 

particular product; and making small volumes of a product in a batch process part of the year and 

making large volumes in a continuous process part of the year. A facility would need to develop 

a representative emissions factor for each process operating scenario because each operating 

scenario for a process will result in different emissions levels. 

Prior to developing an emissions factor, facilities should observe the operating conditions 

of the process over a period of time and note how changes to the operating conditions affect 

emissions rates. The time periods may vary from facility to facility and perhaps from process to 

process, but typically may include an examination period of one year or one month and could 

include examination of startup and shutdown periods. An examination of the previous year of 

process operating conditions might take note of whether there is month-to-month or seasonal 

variability in the process. For example, seasonal variability might be caused by production rate 

changes or might be caused by changes in the ambient temperature from summer to winter. An 

examination of one month of process operating conditions might reveal some short-term process 

variability. A review of startup and shutdown process operating conditions may include an 

assessment of how frequently startups and shutdowns occur, what effect startups and shutdowns 

have on emission rates, and whether or not the impact on emissions can be quantified. 

In general, emissions testing during process startups and shutdowns would not be 

expected to lead to representative emission factors, because emission rates tend to fluctuate 

during such events. Exceptions to this could include long-term monitoring that would not over35 
represent startup or shutdown conditions in the resulting emission factor, and monitoring 

specifically to obtain emission factors for startups and shutdowns conditions. Several companies 

indicated that they have analyzed the emissions profile during startup events and during 

shutdown events. They found that the emission rates during these events departed from those at 

steady state conditions, but that emissions profiles were consistent between one startup event and 

another. 

Number of samples 

Emission samples should be taken over the full range of process conditions within a 

given operating scenario. To assess the variability of emission rates within the operating 

scenario, a minimum of three emission test runs is appropriate. If the emission factors based on 

the three test runs show relatively little variability, i.e., if their relative standard deviation (RSD) 

is low, then the three sample emission factors can probably be averaged to obtain a robust, 

representative emission factor for the process. However, if the emission factors based on the 

three test runs show high variability, that is, a high RSD, then the average of the three emission 

factors may be a poor estimator of the actual mean emission rate from the process. In this case, 

additional samples should be taken to develop a robust emission factor.13 The equation to 

estimate the RSD is shown in Equation RSD-1. 

EF

RSD = s (Eq. RSD-1) 

Where: 

RSD = Relative standard deviation, fraction 

s = sample standard deviation, calculated in Eq. RSD-2 

EFbar = average emission factor for all test runs combined 

Equation RSD-2 is used to estimate the sample standard deviation, s. 

( ) ( ) ( )

1

... 1 2 3

−

+−+−+− = nEFEFEFEFEFEF

s

2 2 2

 

 (Eq. RSD-2) 

Where: 

s = sample standard deviation 

EFi = the individual emission factor value from test run 1, 2, 3, etc. 

EFbar = average emissions factor across all test runs (sample mean emission factor), 

calculated in Equation RSD-3 

13 The fact that emission rates from a process show high variability does not mean that a representative emission 

factor cannot be developed; it simply means that more samples must be taken to do so. Note, however, that if the 

variability of the process can be attributed to the variability of a controllable and measurable process parameter, it is 

probably appropriate to develop one or more additional operating scenarios, each with its own emission factor, to 

capture this variability. 

36 
n = number of test runs 

Eq. RSD-3 (which corresponds to equation L-20 in the regulatory text) is used to estimate 

the mean emissions factor, EFbar. 

n

EF EFEFEF 321 + + + ... = (Eq. RSD-3) 

Where: 

EFbar = average emissions factor for all test runs combined (sample mean emission factor) 

EFi = the individual emission factor value from test run 1, 2, 3, etc. 

n = number of test runs 

In general, more samples are required to characterize the mean of a population or 

parameter that has high variability than are required for a population or parameter that has low 

variability. The number of samples required to estimate the mean of the parameter with a given 

level of confidence can be calculated based on the RSD of the samples and on some assumptions 

about the distribution of the parameter. Where the set of samples is relatively small and only the 

sample standard deviation “s” is known (rather than the true standard deviation of the 

parameter), the appropriate statistic is often the Student’s t test. The Student’s t test presumes an 

approximately normal, bell-shaped distribution of the underlying parameter, which implies that 

the distribution of the average is the Student’s t distribution. 

For this situation, the Student’s t test can be written: 

( )

statistic CI

T

statistic CI t

n

s

EFEF

t − %95 +< − %95

⎟

⎟

⎟

⎟

⎠

⎞

⎜

⎜

⎜

⎜

⎝

⎛

− − < (Eq. RSD-4) 

Where: 

EFbar = Average emission factor across all test runs (sample mean emission factor) 

EFT = True mean emission factor of the process 

s = Sample standard deviation 

n = Number of samples 

tstatistic-95%CI = Value of student’s t statistic chosen to represent a 95-percent confidence 

interval with n-1 degrees of freedom. For a sample size of 3, this value is 

4.30. 

Dividing through by the sample mean emission factor, EFbar, we obtain: 

37 
( )

statistic CI

T

statistic CI t

n

RSD

EFEFEF

t %95 %95

/ − +< −

⎟

⎟

⎟

⎟

⎠

⎞

⎜

⎜

⎜

⎜

⎝

⎛

− − < (Eq. RSD-5) 

To choose a RSD above which we will require more than three samples, we first decide 

how much error we are willing to tolerate in our emission factor. Suppose we want the emission 

factor to have a 95 percent chance of being within 30 percent of the true mean emission rate of 

the process. The requirement for the emission factor to be within 30 percent of the true mean 

emission rate can be expressed as follows: 

( − EFEFEF ) < 3.0/)( T (Eq. RSD-6) 

Equation RSD-5 can also be rearranged as follows: 

( ) T statistic CI t

n

EFEFEF *

%95 /)( − < −

RSD (Eq. RSD-7) 

Subtracting Equation RSD-7 from Equation RSD-6, we obtain: 

statistic CI t

n

−< *3.00 − %95

RSD

Plugging in the values for t and n and solving for RSD, we obtain 

> RSD

3.4

3*3.0

12.0 > RSD

We conclude that if the RSD exceeds 0.12 (or 12 percent), we should test more than three 

samples. Unfortunately, it may be difficult to obtain an RSD of less than 0.12 even when the 

real emission rate is nearly constant. This is because the error of the concentration 

measurements used in the testing can be near 10 percent. Thus, we might want to consider 

whether we can tolerate a somewhat higher error in our emission factor.14 If we require that the 

emission factor be within 40 percent of the true mean emission rate and solve the above 

equation, we arrive at the conclusion that we should test more if the RSD exceeds 0.16 (16 

percent). If we require that the emission factor be within 50 percent of the true mean emission 

rate (with 95-percent confidence) and solve the above equation, we arrive at the conclusion that 

we should test more if the RSD exceeds 0.20 (20 percent). 

 

14 Another approach to minimizing the error is to require more samples initially, e.g., 4 instead of 3. With 4 initial 

samples, the emission factor has a 95 percent chance of being within 30 percent of the true mean emission rate if the 

RSD is less than 19 percent. 

38 
With an additional three samples (n=6), the uncertainty of the emission factor declines 

significantly. For n = 6, Equation RSD-5 becomes: 

( ) 57.2

6

/ 57.2 +<

⎟

⎟

⎟

⎟

⎠

⎞

⎜

⎜

⎜

⎜

⎝

⎛

− <− RSD

T EFEFEF

Plugging an RSD of 0.20 (20 percent) into this equation, we find that after six samples, 

there is a 95 percent chance that the sample mean (emission factor) is within 21 percent of the 

true mean (average emission rate of the process). 

4. Updates to emission factors and emission calculation factors. 

The emission rate from a process is likely to change as the process evolves or is altered. 

Process changes that can affect the fluorinated GHG emission rate include changes in raw 

materials, equipment, production levels, or operating conditions. These changes can occur all at 

once or gradually, over time. Facilities that have measured and re-measured their emission 

factors over a period of several years have found that gradual, incremental changes to the process 

(e.g., to improve yields) have significantly changed emission factors15. To ensure that emission 

factors and emission calculation factors continue to accurately represent emission rates, they 

should be updated when significant process changes occur. In addition, it may be appropriate to 

update emission and emission calculation factors at regular intervals (e.g., five to ten years) to 

capture the cumulative impact of small changes to the process. 

5. Potential Process Vent Emission Threshold. 

In discussions with EPA, representatives of fluorinated gas producers stated that more 

effort and resources should be expended to accurately estimate the size of large emission streams 

than to estimate the size of small ones. Consistent with this principle, EPA evaluated process 

vent emissions cutoffs above which facilities would be required to conduct emissions testing to 

develop a site-specific emissions factor and below which facilities could conduct emissions 

calculations to develop a site-specific emissions factor. 

There are various rules for other regulatory programs that have established emission 

cutoffs above and below which there are different control, monitoring, and reporting 

requirements. For example, there are process or process vent cutoffs in various NESHAP rules 

in 40 CFR part 63, such as subpart GGG for Pharmaceutical Manufacturing, subpart FFFF for 

Miscellaneous Organic NESHAP (MON), and subpart VVVVVV for Chemical Manufacturing 

Area Source rule. Because some producers mentioned the rule requirement cutoffs in subpart 

FFFF, Miscellaneous Organic NESHAP (MON), the initial step in the cutoff development was 

reviewing the 10,000 lb/yr (i.e., 5 ton/yr) of uncontrolled organic HAP emissions cutoff for 

processes in that rule. (While these data and facility practices for the MON source category may 

not be completely analogous to the data and practices at fluorinated gas production facilities, this 

information was used to inform the reporting rule-making process.) Similar to the fluorinated 

gas production industry, the MON source category includes both continuous and batch processes. 

 

15 Based on conversations with Fluorinated GHG producers, as referenced in Section 7.

39 
At the MON facilities, we looked at the emissions levels of MON process vents to identify the 

number of vents covered and the emissions covered by various cutoffs. For continuous 

processes, approximately 26 percent of process vents have emissions greater >10,000 lb/yr and 

more than 99 percent of the total organic HAP emissions from continuous process vents occur 

from these vents. For batch processes, 13 percent of batch process vents have emissions >10,000 

lb/yr and the organic HAP emissions from these vents are 96 percent of the total organic HAP 

emissions from batch process vents. The 10,000 lb/yr organic HAP cutoff for requiring control 

of the process vent in the MON rule provides a good balance for minimizing the number of 

process vents required to implement control and maximizing the emissions covered or captured 

by the rule. 

In evaluating cutoffs for the process vents in the fluorinated gas production source 

category, we began by analyzing a 10,000 lb/yr fluorinated GHG uncontrolled emissions cutoff. 

Because the quantities of these emissions in terms of CO2e would vary significantly depending 

on the specific fluorinated GHG compound emitted and its GWP, we decided to evaluate the 

cutoff in terms of CO2e. We assumed an average GWP of approximately 2,000 for the 

fluorinated GHG, and given the cutoff value of 10,000 lb/yr fluorinated GHG, we developed a 

cutoff of 10,000 mt CO2e. Process vents above the 10,000 lb/yr limit would be required to 

conduct an emissions test to develop a site-specific emissions factor for the vent, and process 

vents below the 10,000 mt CO2e could develop a site-specific emissions calculation factor based 

on engineering calculations or engineering assessments. 

 Depending on the specific fluorinated GHG emitted, the emissions of the fluorinated 

GHG in terms of the actual gas could vary significantly. In Table 4, the emissions in terms of 

the fluorinated compounds that are translated from the CO2e cutoff are shown. The fluorinated 

compounds are shown in order of increasing GWP. For example, for fluorinated GHG 

compounds as diverse as HFC-134a to SF6, the cutoff of 10,000 mt CO2e would translate into 

fluorinated GHG emissions ranging from 16,962 lb/yr to 923 lb/yr, respectively. However, the 

detection limits of fluorinated GHG, depending on process vent flow rates, are likely sufficiently 

low to allow detection and quantification of these compounds at these emission levels. 

The emission threshold for process vents could also be based on controlled emissions, for 

example, emission levels considering destruction efficiency are less than 10,000 mtCO2e on an 

annual basis. 

Another potential approach for selecting a process vent cutoff might include a combined 

approach, i.e., meeting both a CO2e emissions cutoff and also a cutoff in terms of pounds of 

fluorinated GHG. For example, if a process vent had emissions less than 25,000 mt CO2e and 

also less than 10,000 lb of fluorinated GHG emissions, i.e., the process vent meets both criteria, 

then it would be considered below the cutoff. 

An issue related to setting a process vent cutoff based on CO2e is related to fluorinated 

GHGs that do not have published GWP. In this instance, a lower level cutoff could be 

established for those fluorinated GHG whose GWP does not appear in Table A-1 of 40 CFR part 

98 subpart A, for example, less than 1 metric ton for emissions that include a compound without 

GWP. In addition, an average GWP, e.g., average GWP of 2,000, could be applied for all 

fluorinated GHG whose GWP does not appear in Table A-1 of 40 CFR part 98 subpart A. 

40 
Table 4. Analysis of Uncontrolled Process Vent Cutoffs: Translate Emissions from CO2e to 

Pounds of Fluorinated GHG, and vice versa.1

Vent limit in 

mtCO2e 

In pounds of fluorinated GHG: 

HFC-134a HFC-125 HFC-143a CF4 C2F6 NF3 SF6 

Convert CO2e vent cutoff to lb of fluorinated GHG 

25,000 42,404 * 19,688 * 14,507 * 8,481 5,992 3,205 2,306 

20,000 33,923 * 15,750 * 11,605 * 6,785 4,793 2,564 1,845 

10,000 16,962 * 7,875 5,803 3,392 2,397 1,282 923 

5,000 8,481 3,938 2,901 1,696 1,198 641 461 

Vent limit in 

pounds of 

fluorinated 

GHG 

In mtCO2e: 

HFC-134a HFC-125 HFC-143a CF4 C2F6 NF3 SF6 

Convert lb of fluorinated GHG to mt CO2e 

10,000 5,896 12,698 17,234 29,478 * 41,723 * 78,005 * 108,390 * 

5,000 2,948 6,349 8,617 14,739 20,862 39,002 54,195 1 The GWP for fluorinated GHG are HFC-134a is 1,300; HFC-125 is 2,800; HFC-143a is 3,800; CF4 is 6,500 C2F6 is 

9,200; NF3 is 17,200; and SF6 is 23,900. 

* denotes that the level exceeds a 10,000-lb cutoff (in top table) or a 10,000-mtCO2e cutoff (in bottom table). 

6. Process Vent Preliminary Emission Estimates. 

To determine whether a process vent is above or below the 10,000 mt CO2e threshold, 

facilities could use any of several emission estimation methods discussed above. In this 

preliminary step, it seems reasonable to allow use of engineering calculations or engineering 

assessments similar to those identified in Section 3.B.iii.2 to determine the emissions of 

fluorinated GHG from the process. Acceptable calculation methods for uncontrolled and 

controlled process vent emissions may include those from various rule text or guidance 

documents, such as the MON, Pharmaceutical, and other examples provided in Section 3.B.iii.2 

above. 

Engineering assessments are another reasonable approach to determining preliminary 

emissions from process vents. Engineering assessments include the types of information 

discussed in Section 3.B.iii.2 above (previous test data, bench-scale or pilot-scale test data, 

design analysis, etc.) Facilities typically have component and composition data available from 

the original research and development activities on the process and from the process’ lifetime of 

operation. For process vent emissions determinations, facilities could conduct an engineering 

assessment to calculate uncontrolled emissions for each process vent and for each emission 

episode, and apply destruction efficiencies for periods of control, as applicable. 

7. Current Plant Practices for Process Vent Monitoring 

Several facilities with fluorinated gas production processes have indicated that they 

conduct monitoring and analysis on individual process vents and that they characterize streams 

from processes. They typically develop facility-specific or process-specific EFs and track 

production activity data to estimate fluorinated GHG emissions. 

Facilities indicated that a variety of approaches are used to estimate fluorinated GHG 

emissions and develop process-specific emissions factors, including sampling and measurement 

41 
(i.e., direct testing) and chemical engineering calculations and estimates. At most facilities, a 

combination of these approaches is used to estimate fluorinated GHG emissions from the various 

process vents at the site. Some facilities indicated, for example, that facility staff measure the 

concentrations and flows for reactor vessel process vents and conduct engineering calculations to 

estimate concentration and flows from process dryers. Engineering calculations are based on 

common chemical engineering principles and empirically based data and process knowledge. 

The engineering calculations may also be based on emission estimation equations contained in 

rules, for example in the Pharmaceutical NESHAP, or may be conducted using purchased 

process modeling software packages, such as ASPEN and EmissionsCalculator. 

Facilities indicated that each of these approaches, emission testing and engineering 

calculations, are valid and produce reasonable fluorinated GHG emission estimates and that 

flexibility in which approach is applied to any particular process vent is appropriate. Facilities 

particularly noted that they match the level of effort and “rigorousness” in the emissions 

determination approach with the emissions source size. That is, they devote more effort to 

characterizing emissions from relatively large fluorinated GHG emissions points, pursuing 

emissions testing for these sources, and less effort to characterizing emissions from relatively 

small fluorinated GHG emissions points, applying engineering calculations to these sources. 

Some facilities noted that certain process vents are not measured directly because the emission 

stream contains a compound that is hazardous for plant and personnel safety, e.g., if HF is 

present in a stream. The facilities noted that emission points that are not safe to measure are 

typically estimated from chemical engineering calculations and from process design data. In 

using FTIR instruments, some vendors have noted that specialty glass sample cells are available 

that are more resistant to HF. Some facilities noted that measuring fluorinated organics can be 

done easily if the HF can be removed from the sampling stream. One option may be to flow the 

sample stream through containers of water to remove HF prior to measuring the fluorinated 

organic. While this approach may be successful at measuring the fluorinated organic, the flow 

rate of the stream cannot be determined with any accuracy. This approach also does not alleviate 

the personnel safety concerns. 

Facilities further expanded on the use of previous stream analysis results as appropriate 

data to be used. Generally, facilities have a good understanding of the chemistry for all 

processes and understand what raw materials are fed to the process, what side reactions occur, 

and what products and by-products are created. Facilities have laboratory scale, pilot plant, and 

full scale streams analysis results. Facilities noted that in particular, at the bench-scale phase of a 

product and process development, they analyze all streams to identify all species and compounds 

such as product, byproducts, and waste. The process design from when the process was 

originally developed and built is detailed, and more recently installed processes will have 

excellent design and chemistry documentation available. Older processes may tend to have less 

detail. 

Facilities indicated that they typically conduct an initial analysis to develop the processspecific emission factor or emission calculation factor and do not continuously measure and 

calculate emissions from process vents and streams. When there is a process change, i.e., a 

change in the operating conditions or a change in the process equipment used, they will conduct 

a reanalysis of the process. Facilities pointed out that prior to making process change, they 

analyze the theoretical chemistry and predict the likely changes in the set of fluorinated GHG 

42 
compounds generated and in the fluorinated GHG emissions levels. They typically begin with 

engineering calculations to determine the impacts of the change on species generated or emission 

levels, and follow that with retesting and recalculations when appropriate. Some facilities noted 

that after a process change, they will sample and analyze to identify every species or compound 

generated, in either process vents or process streams. 

8. Potential use of continuous emissions monitors to measure emissions from vents. 

Another potential monitoring option EPA considered was requiring that facilities measure 

emissions from fluorinated gas production facilities using continuous emissions monitors 

(CEMS). If properly selected and maintained, CEMS would be expected to provide estimates of 

emissions more accurate than either the mass-balance or the process-vent approach. Under this 

approach, facilities would install and operate CEMS capable of measuring fluorinated GHGs to 

measure process emissions. The requirements for the CEMs would be similar to those in subpart 

C, adjusted, as appropriate, to accommodate CEMS for fluorinated gases. One possible option is 

to use Fourier Transform Infrared Spectrometers (FTIRs) CEMS in scrubber stacks to measure 

emissions. FTIR spectroscopy is presently used to conduct short-term fluorinated GHG emission 

measurements from processes. In recent discussions with FTIR CEMS vendors, they noted that 

the units can operate continuously. Some units require liquid nitrogen cooling and the liquid 

nitrogen vessel (dewar) has a limited capacity. These nitrogen cooled units can operate for up to 

12 hours on a single charge (nitrogen), and continuous operation of the unit could be achieved 

through the use of an extended dewar with an automated fill cycle. With the extended dewar, the 

unit can operate for approximately 3 days. (The detector is nitrogen cooled, and a dewar, which 

is an insulated container with a vacuum between its inner and outer layers, is used to hold the 

liquid nitrogen.) FTIR CEMS vendors noted that the sample cell can be adjusted to 

accommodate concentration levels, where a shorter cell length can be used for higher 

concentrations and longer cell lengths can be used for lower concentrations. Another option for 

high concentrations might include use of dilution and a standard cell. The vendor typically sets 

up a software package based on the compounds expected in the measured vent, and the software 

is revised for other compounds as needed. 

However, potential drawbacks to requiring CEMS are that they would be relatively 

expensive to install and they may not tolerate the acidic and reactive environments (e.g., high HF 

concentration) found in vents at many fluorinated gas production facilities. Some FTIR CEMS 

vendors utilize specially configured gas cells that run hot and utilize mirror coatings to protect 

the cell from high HF concentrations and use special types of unit seals (o-rings) that are inert to 

corrosive compounds. In any case, vendors noted that HF in the vent streams is a common 

problem, and that HF concentrations in the percent range are a difficult issue to deal with. The 

latter concern might be mitigated by installing CEMS after a scrubber, if this is practicable. 

Given these potential concerns, it may be appropriate to require CEMS for particularly large 

emission streams, e.g., those resulting in emissions of more than 50,000 mtCO2e annually. 

9. Equipment Leak Emissions Estimates. 

Process vents are only one of several sources of fluorinated GHG emissions at fluorinated 

gas production facilities. Another potentially significant source is equipment leaks, whose 

emissions do not occur through process vents. Emissions from equipment leaks may be 

estimated using EPA Method 21, EPA Protocol for Equipment Leak Emission Estimates (EPA43 
453/R-95-017) (EPA Protocol for Equipment Leaks), and other validated methods and 

procedures capable of detecting the analyte of interest at the concentration of interest. Leak 

monitoring could be performed periodically, which typically would be quarterly, semi-annually, 

or annually. Due to the nature and scope of the reporting rule, which is focused on monitoring 

and emission estimation rather than on leak repair (control), equipment leak monitoring on an 

annual basis should be sufficient. The EPA Protocol for Equipment Leaks includes four methods 

for estimating equipment leaks. These are, from least to most accurate, the Average Emission 

Factor Approach, the Screening Ranges Approach, EPA Correlation Approach, and the UnitSpecific Correlation Approach. The Average Emission Factor Approach relies on emission 

factors and equipment counts, the service of each component, the composition of the stream, and 

the length of time the equipment was in service to estimate emissions, and does not require any 

real-world data be collected from the processes. The remaining three methods, The Screening 

Ranges Approach, EPA Correlation Approach and the Unit-Specific Correlation Approach all 

depend on the collection and use of facility-specific and process-specific screening data to 

estimate emissions. 

To use these three screening data methods, the facility would need to have (or develop) 

Response Factors relating concentrations of the target fluorinated GHG (or surrogate gas cooccurring in the stream) to concentrations of the gas with which the leak detector is calibrated. 

Our understanding is that flame ionization detectors (FIDs) are generally insensitive to 

fluorinated GHGs, and that they are therefore not likely to be effective for detecting and 

quantifying fluorinated GHG leaks. An exception to this would be a situation in which the 

fluorinated GHG occurred in a stream along with a substance (e.g., a hydrocarbon) to which the 

FID was sensitive; in this case, the other substance could be used as a surrogate to quantify leaks 

from the stream. We understand that at least two fluorocarbon producers currently use methods 

in the EPA Protocol for Equipment Leaks to quantify their emissions of fluorinated GHGs with 

different levels of accuracy and precision. Other analytical techniques that are sensitive to 

fluorinated compounds may be available to monitor concentrations of equipment leaks, including 

photoionization, ultraviolet, infrared, and others. 

A preliminary review revealed a handful of detectors capable of detecting fluorinated 

GHGs. While some fluorinated GHGs can be detected using instruments that meet EPA Method 

21 specifications, others cannot. These detectors use various operating principles, including, 

infrared, photoionization and ultraviolet detection. Although instruments for detecting leaks of 

HFCs and SF6 from air-conditioning, refrigeration, and electrical equipment have existed for 

some time, most of these instruments do not quantify emissions and/or detect only one or two 

gases. In many cases, therefore, these instruments are not capable of quantifying emissions of 

the broad range of fluorinated GHGs that can leak from process equipment in fluorinated gas 

production facilities. One issue that arose with these detectors was their high sensitivity. For 

some of the equipment, maximum readings were well below the 10,000 ppm leak/no-leak 

threshold of the Screening Ranges Approach, meaning that the Screening Ranges Approach 

could not be used with these detectors. Those capable of reading the 10,000 ppm concentration 

had sampling rates that exceeded the rates established by Method 21. However, the EPA 

Correlation Approach and the Unit-Specific Correlation Approach could be used with these 

detectors, assuming that the detectors do not hit their maximum readings (peg) in the facility. 

44 
Under the preliminary review of detectors, EPA did not identify equipment capable of 

detecting and quantifying all fluorinated GHG emissions that can also meet all of the Method 21 

specifications, or found that the equipment reaches its maximum (“pegs”) at relatively low 

concentrations. In general, in identifying the need for alternatives to EPA methods, EPA 

discovered that the equipment and methods for detecting and quantifying emissions of 

fluorinated GHGs from equipment leaks have not advanced as far as those for monitoring 

emissions of VOC from equipment leaks. Additional alternatives for monitoring of equipment 

leaks beyond Method 21 and the EPA Protocol for Equipment Leaks are likely warranted. For 

example, facilities could monitor leaks using other approaches such as soap bubble testing 

combined with the Average Emission Factors or the Screening Ranges Approach; use of 

alternatives allowed under other regulatory programs, such as alternative leak detection methods 

in 40 CFR 63, 63.1036, alternative means of emission limitations: batch processes; or use of 

alternative work practices using optical imaging combined with Average Emission Factors. One 

facility noted that they conducted room air exhaust monitoring to identify emissions from 

equipment leaks and simultaneously conducted direct monitoring of pieces of equipment in 

service within the room; the analytical results from the room air exhaust showed that 

concentrations were at non-detect levels for all but one or two F GHG compounds, and the 

monitoring of pieces of equipment showed non-detect levels for all but one or two F GHG. In a 

monitoring approach for room air exhausts, facilities would need to explain how the approach 

accounts for variations in concentrations in the room air and possibility that some emissions may 

not be accounted for in the measurements (i.e., concentrations below non-detect levels due to 

large room air volume or room air exhaust gas flow). 

Another approach for monitoring leaks from pieces of equipment may include use of the 

Alternative Work Practice (AWP) for EPA Method 21 (similar to monitoring requirements under 

40 CFR part 60, subpart A, §40 CFR part 60.18; 40 CFR part 63, subpart A, §40 CFR part 63.11; 

or 40 CFR part 65, subpart A, §40 CFR part 65.7). This approach would include monitoring 

leaking equipment with an optical gas imaging instrument. Emissions from those pieces of 

equipment found to be leaking could be estimated based on emission factors. Under this 

approach, facilities could image each piece of equipment in fluorinated GHG service, and all 

emissions imaged by the optical gas imaging instrument would be considered leaks and would be 

subject to emissions estimation. 

Several fluorinated gas producers have indicated that equipment leaks account for a small 

share of facility-wide fluorinated GHG emissions. Although this generalization is largely based 

on experience with VOC and HAP, two fluorinated gas producers have surveyed at least some of 

their process equipment with detectors sensitive to fluorinated GHGs and have found a similar 

low level of emissions. 

10. Container Heel Venting 

In addition to the emission sources mentioned above, the venting of container or cylinder 

heels is an additional source of fluorinated GHG emissions. Emissions from returned containers 

and from recycling depend heavily on the practices of individual facilities. If the facility 

recovers container heels or simply refills containers on top of heels, then emissions from 

returned containers will be small. However, if the facility vents heels, then emissions can be 

significant, even dominating overall facility emission rates. 

45 
According to the 2006 IPCC Guidelines 16, SF6 production operations in Germany whose 

customers did not require highly purified gas had emission rates in the range of 0.2 percent of the 

total quantity of SF6 produced. On the other hand, SF6 production operations in Japan whose 

customers required highly purified gas had emission rates of 8 percent due to the venting of heels 

whose purity was in doubt. 

An analysis of the possible emissions from venting of residual fluorinated GHGs in 

containers showed that these emissions could be significant. Cylinder heel venting was assumed 

to occur only for fluorinated GHG that are used in etch and chemical vapor deposition chamber 

clean processes in electronics. Because the electronics industry requires extremely high purity 

for these etch and chamber clean gases, fluorinated gas producers may be reluctant to recycle 

them, because recycling could inadvertently introduce impurities. Chemicals made in U.S. that 

are used in etch and chamber clean processes include CF4, C2F6, C3F8, c-C4F8O, CHF3 (HFC-23), 

NF3, SF6.

17 A total of 6 companies produce these etch and chamber clean gases at 7 facilities in 

the U.S. To estimate the annual emissions from cylinder heel venting, it was assumed that 100 

percent of the production of each of these chemicals, except SF6, was used in electronics. For 

SF6, it was assumed that approximately 10 percent of SF6 production was used in electronics, 

based on historical SF6 usage patterns. For 2006, the total production of etch and chamber clean 

fluorinated GHG listed above, including 10 percent of the SF6 production, was over 60 million 

mtCO2e. Assuming that half of the producing facilities are venting cylinders and emit a 10 

percent heel, the emissions from cylinder heel venting are estimated to be approximately 3 

million mtCO2e. 

The situation is similar for recycling. Emissions during recycling include emissions 

during transfer of gas from containers to process equipment, but they also include emissions 

associated with ridding the gas of contaminants, such as noncondensables (air, nitrogen, etc.) and 

oil. (Since lubricants are chosen to be miscible with refrigerants, a significant quantity of 

refrigerant can remain mixed into the oil when the oil is removed from the system or container.) 

If facilities carefully recover and purify gas that is returned for recycling, emissions are likely to 

be in the neighborhood of one percent or less of the quantities returned.18 However, if facilities 

use crude methods to purge noncondensables from containers, e.g., venting from the headspace 

of the cylinder, or if they don’t attempt to minimize fluorinated GHG emissions from lubricants, 

then emissions can be closer to five or ten percent of the quantities returned. (Early standards for 

recycling equipment allowed emissions from purging as high as five percent;19 these limits have 

been lowered considerably since.) In the worst case, facilities could simply vent returned 

fluorinated GHGs, e.g., in cases where they are irretrievably contaminated. 

 

16 From IPCC 2006, 2006 IPCC Guidelines for National Greenhouse Gas Inventories, Prepared by the National 

Greenhouse Gas Inventories Programme, Eggleston H.S., Buendia L., Miwa K., Ngara T. and Tanabe K. (eds). 

Published: IGES, Japan., page 3,104 of Volume 3, Industrial Processes and Product Use. 

17 CH2F2 (HFC-32) is also made in the U.S. and is used in etch and clean, but the fraction of the gas used for this 

purpose was not known and therefore it was not included in the total (although it is expected to comprise a small 

share of the total). 

18 From IPCC Volume 3, Chapter 8. http://www.ipccnggip.iges.or.jp/public/2006gl/pdf/3_Volume3/V3_8_Ch8_Other_Product.pdf 

19 SAE J1990, 1989 Extraction and Recycle Equipment for Mobile Automotive Air-Conditioning Systems; ARI 

Standard 740-1993, For Performance of Refrigerant Recovery and/or Recycling Equipment. 

46 
To estimate fluorinated GHG emissions from container venting, facilities could either 

measure the emissions vented from each container or develop site-specific emission factors, i.e., 

a heel factor, for each combination of fluorinated GHG, container size, and container type that 

are vented. To measure the fluorinated GHG emissions, a facility would make a measurement 

for each container, either by weighing the container or by measuring the pressure of the container 

and calculating the mass using an equation of state. 

The total emissions for venting of residual fluorinated GHG from containers may be 

summed at the facility based on the number of containers received and vented. Equation L-32 

could be used to calculate the annual emissions of each fluorinated GHG... 

 (Eq. L-32) 

Cf Bfj −= ∑∑ HHE Efj

1 1

n n

Where: 

ECf = Total mass of each fluorinated GHG f emitted from the facility through venting of 

residual fluorinated GHG from containers, annual basis (kg/year). 

HBfj = Mass of residual fluorinated GHG f in container j when received by facility. 

HEfj = Mass of residual fluorinated GHG f in container j after evacuation by facility. 

(Facility may equate to zero.) 

n = Number of vented containers for each fluorinated GHG f. 

A facility could develop heel factors based on representative samples of the containers 

received by the facility from fluorinated GHG users. A facility would select a representative 

sample of containers for each combination of fluorinated GHG, container size, and container 

type that a facility vents. A representative sample would reflect the full range of quantities of 

residual gas returned in that container size and type. To determine the residual weight or 

pressure, facilities could monitor the mass or the pressure of your cylinders/containers. If the 

facility monitors the pressure, the ideal gas law in equation L-33 would be used to convert the 

pressure to mass. 

 pV=ZnRT (Eq. L-33) 

Where: 

p = Absolute pressure of the gas (Pa) 

V = Volume of the gas (m3

) 

Z = Compressibility factor 

n = Amount of substance of the gas (moles) 

R = Gas constant (8.314 Joule/Kelvin mole) 

T = Absolute temperature (K) 

47 
Facilities would use the container residual mass for each specific fluorinated GHG to 

determine what mass fraction of the initial mass in the container is vented. 

Facilities would then calculate the annual fluorinated GHG emissions based on the gasspecific heel factor and the number of containers that are returned to the facility, using Equation 

L-34. 

∑ (Eq. L-34) =

=

n

j

Cf FNhE fjfjfj

1

**

Where: 

ECf = Total mass of each fluorinated GHG f emitted from the facility through 

venting of residual fluorinated GHG from containers, annual basis (kg/year). 

hfj = Facility-wide gas-specific heel factor for input gas f (fraction) and container 

size and type j, as determined in §98.124(j) of this subpart. 

Nfj = Number of containers of size and type j returned to the fluorinated gas 

production facility. 

Ffj = Full capacity of containers of size and type j containing fluorinated GHG f 

(kg). 

n = Number of combinations of container sizes and types for fluorinated GHG f. 

 

11. Destruction Efficiency Testing 

It may be appropriate to require that fluorinated gas producers that destroy F-GHGs 

conduct emissions testing periodically, for example every five or ten years, to determine the 

destruction efficiency (DE) of the destruction device. The testing for determining the DE would 

be similar to the emissions testing that could be conducted to develop site-specific process-ventspecific emission factors. Facilities would need to conduct testing that shows the destruction 

device can successfully destroy emissions at worse-case operating conditions, for example when 

operating at high loads reasonably expected to occur and when destroying the most-difficult-todestroy fluorinated GHG fed into the device (or when destroying a surrogate that was more 

difficult to destroy than that fluorinated GHG). The last point is particularly important because 

some fluorinated GHGs (e.g., CF4, SF6

20 and other PFCs) are extremely difficult to destroy; DEs 

determined for other fluorinated GHGs (or for typical Class 1 POHCs) would overestimate the 

destruction of these fluorinated GHGs. 

For destruction of fluorinated GHG compounds to occur, temperatures must be quite 

high, fuel must be provided, flow rates of fuels and air (or oxygen) must be kept above certain 

limits, flow rates of fluorinated GHG must be kept below others, and for some particularly 

 

20 For example, SF6 ranks 4th in the Class 1 incinerability rankings of the Office of Research and Development and 

Office of Solid Waste and Emergency Response of U.S. Environmental Protection Agency’s Guidance on Setting 

Permit Conditions and Reporting Trial Burn Results Handbook, Volume II. EPA Publication No. EPA/625/6-

89/019. January 1989. 

48 
difficult-to-destroy chemicals, pure oxygen must sometimes be fed into the process. If one or 

more of these process requirements is not met, destruction efficiencies can drop sharply (in some 

cases, by an order of magnitude or more), and fluorinated GHGs will simply be exhausted from 

the device. For more discussion of this issue, see the Technical Support Document for Industrial 

Gas Supply: Production, Transformation, and Destruction of Fluorinated GHGs and N2O, Docket 

number EPA-HQ-OAR-2008-0508-041. 

In the destruction and removal efficiency testing that is performed at hazardous waste 

combustors pursuant to part 63, subpart EEE, facilities that demonstrate 99.99 percent DRE for a 

POHC within a thermal stability class are typically allowed to assume that 99.99 percent DRE 

would also be achieved for the other compounds in that class and for compounds in other thermal 

stability classes with lower thermal stability rankings. This approach is based on the general 

conclusion that, for POHCs that are in the same class and that occur in significant volumes, 

differences in DREs tend to be small, and that compounds in other thermal stability classes with 

lower stability rankings are easier to destroy. 

However, it would be a misapplication of the thermal stability index to conclude that a 

combustor that has demonstrated 99.99 percent DRE for any Class 1 compound21 would also 

achieve 99.99 percent DRE for SF6, a Class 1 compound, and for perfluoromethane (CF4). 

While achieving 99.99 percent DRE for SF6 ensures 99.99 percent DRE for other Class 1 

compounds, the converse may not be true. SF6 is substantially more thermally stable than other 

Class 1 compounds (and CF4 is substantially more thermally stable than SF6). 

The theoretical considerations that support the conclusion that fluorinated GHGs are 

extremely thermally stable relate to the high energies of the C-F and S-F bonds. These energies 

make it difficult to break the bonds through reaction with oxygen, hydrogen, or the hydroxyl 

radical, the typical means of destroying other class 1 compounds. Essentially, the only path 

available to destroy these fully fluorinated compounds in hazardous waste combustors or thermal 

oxidizers is through thermal decomposition at very high temperatures.22 These temperatures are 

significantly higher than those required for the thermal decomposition of most other class 1 

compounds. For SF6, the thermal stability index indicates that the temperature to achieve 99 

percent destruction with a two-second residence time is 1,090°C; for CF4, we project that the 

temperature would be on the order of 1,380°C.23 Researchers have suggested that CF4 may 

break down only in the flame zone.24 

Experimental evidence supports the idea that SF6 and CF4 are difficult to destroy. Due in 

part to the theoretical considerations outlined above, several studies have evaluated the use of 

SF6 as a possible surrogate for POHCs in evaluating DREs. Most studies have verified that the 

DRE measured for SF6 is likely to be lower than that for POHCs, i.e., that it is likely to yield a 

 

21 Class 1 is the group of POHCs and surrogates with the highest thermal stability, meaning they are the most 

difficult compounds to destroy. 

22W. Tsang et al make this case for perfluoromethane in Tsang, W., Burgess Jr., D. R., and Babushok, V. (1998) 

“On the Incinerability of Highly Fluorinated Organic Compounds,” Combustion Science and Technology, 139:1, 

385-402. An analogous argument can be made for sulfur hexafluoride. 

23 SF6 temperature is from Appendix VIII ranking of POHCs; CF4 temperature is estimated based on the rate 

constant provided in Tsang, p. 393. 

24 Tsang, p. 387. 

49 
conservative estimate of the DREs for POHCs under most conditions. In one experiment at a 

full-scale hazardous waste incinerator, the investigators found that even at high-temperature 

conditions, SF6 had a DRE that led to emissions approximately an order of magnitude higher 

than those of other POHCs, including both class 1 and class 2 compounds. At lower-temperature 

conditions, SF6 had a DRE that was over 100 times lower than those of other POHCs.25 As 

noted above, CF4 is even more difficult to destroy than SF6. This has been confirmed in testing 

of point-of-use thermal abatement devices used in electronics manufacturing, which destroyed 

CF4 with an efficiency that was significantly lower (sometimes orders of magnitude lower) than 

the efficiency with which they destroyed SF6.

26

Other fluorinated compounds are not likely to be as stable as CF4 and SF6 because they 

can be dissociated at C-H and C-C bonds (which are weaker than C-F and S-F bonds). 

Nevertheless, higher molecular weight perfluorocarbons such as C2F6 are still expected to be 

relatively difficult to incinerate.27 As is true for CF4, the mechanism of destruction is expected 

to be thermal decomposition rather than attack by radicals, although the decomposition 

temperature will be lower than for CF4 due to the fact that the C-C bond is weaker than the C-F 

bond. 

It may be appropriate to allow facilities to rely on data from destruction device testing 

that has been conducted within the five or ten years prior to the effective date of the rule. 

Facilities that have conducted an emissions test on their destruction device within the five or ten 

years prior to the effective date of the rule may be allowed to use the DE determined during that 

test if the test was conducted in accordance with the proposed test requirements. Facilities could 

also potentially use the DREs determined during principal organic hazardous constituent testing

and hazardous waste combustor testing, provided those tests determined the DRE based on the 

most-difficult-to-destroy fluorinated GHG fed into the device (or based on a surrogate that was 

more difficult to destroy than the most-difficult-to-destroy fluorinated GHG). 

C. Other Potentially Significant Emission Points 

In addition to the fluorinated GHG emissions captured via the Mass Balance method or 

either of the Process Vent methods, other potentially significant emission points exist both 

upstream and downstream of the production measurement. These other emission points under

this source category may include fluorinated GHG emissions from equipment leaks, storage 

tanks, wastewater, container filling (loading), refrigerant blending, and reclamation and recycling 

processes, , particularly where these emissions occur before the production measurement at 

 

25 A. Trenholm, C. Lee, and H. Jermyn, “Full-Scale POHC Incinerability Ranking and Surrogate Testing,” 17th

Annual RREL Hazardous Waste Research Symposium, EPA Office of Research and Development, EPA/600/9-

91/002 April, 1991, pp. 79-88. 

26 USEPA, “Developing a Reliable Fluorinated Greenhouse Gas (F-GHG) Destruction or Removal Efficiency 

(DRE) Measurement Method for Electronics Manufacturing: A Cooperative Evaluation with Qimonda,” March 

2008, EPA 430-R-08-017; USEPA, “Developing a Reliable Fluorinated Greenhouse Gas (F-GHG) Destruction or 

Removal Efficiency (DRE) Measurement Method for Electronics Manufacturing: A Cooperative Evaluation with 

IBM,” June 2009, EPA 430-R-10-004; and USEPA, “Developing a Reliable Fluorinated Greenhouse Gas (F-GHG) 

Destruction or Removal Efficiency (DRE) Measurement Method for Electronics Manufacturing: A Cooperative 

Evaluation with NEC Electronics, Inc.,” December 2008, EPA 430-R-10-005. 

27 Tsang, p. 401. 

50 
fluorinated GHG production facilities. (Equipment leak emissions and container heel evacuation 

are discussed above in separate sections.) 

Fluorinated GHG emissions from wastewater will depend directly on the concentration 

and volume of the contaminants that are present in the wastewater. Based on an evaluation using 

EPA’s Estimation Program Interface (EPI) Suite, approximately 90 percent or more of all 

fluorinated GHG compounds present in wastewater will be emitted to the atmosphere. The 

operating permits for some facilities referred to wastewater treatment activities for fluorinated 

compounds, although it is unclear what level of emissions might occur from wastewater and 

whether there would be wastewater emissions at all facilities. 

The fluorinated GHG emissions from storage tanks are anticipated to be small to 

insignificant due to the use of pressurized tanks for storage. Emissions from blending activities 

are also likely to be relatively small. In both cases, however, emissions can be more significant 

if leaks or catastrophic failures occur. 

Currently, it is EPA’s understanding that most fluorinated GHG production facilities 

measure their production before container filling (loading), e.g., by using flowmeters just 

upstream of the container connection to measure the mass flowing into the containers. If this is 

the case, emissions that occur during or after filling (e.g., from hoses and connections) would 

have been included in the production (supply) measurement. However, if production is 

measured by weighing containers before and after filling, then emissions during container filling 

would not have been included in the production measurement. In these cases, facilities using the 

emission factor approach would need to quantify container filling emissions for completeness. 

The IPCC Guidelines (Volume 3, Chapter 7) estimate that emissions related to container 

management (including refrigerant transfers between containers and handling of returned 

containers) range between 2 and 10 percent of the refrigerant market. 

In the event that the other potentially significant emission points were included under the 

rule, possible methods for tracking these emissions include engineering estimates (e.g., for 

container filling), equipment leak testing (e.g., for storage tanks and blending activities), default 

or site-specific emission factors (all sources), and mass balances (e.g., weighing returned 

container heels). 

4. Procedures for Estimating Missing Data 

In the event that a scale or flowmeter normally used to measure reactants, products, byproducts, or wastes fails to meet a test to verify its accuracy or precision, malfunctions, or is 

rendered inoperable, facilities may estimate these quantities using other measurements where 

these data are available. For example, facilities that ordinarily measure production by metering 

the flow into the day tank could use the weight of product charged into shipping containers for 

sale and distribution as a substitute. It is our understanding that the types of flowmeters and 

scales used to measure fluorocarbon production (e.g., Coriolis meters) are generally quite 

reliable, and therefore that it should rarely be necessary to rely solely on secondary production 

measurements. In general, production facilities rely on accurate monitoring and reporting of the 

inputs and outputs of the production process. In the event that a secondary mass measurement 

51 
for the stream is not available, producers can use a related parameter and the historical 

relationship between the related parameter and the missing parameter to estimate the flow. 

If concentration measurements are unavailable for some period, we are proposing that the 

facility use the average of the concentration measurements from just before and just after the 

period of missing data. 

5. QA/QC Requirements 

Typical QA/QC requirements for measuring devices include initial and periodic 

verification and calibration. (For example, see the requirements of EPA’s Acid Rain regulations 

at 40 CFR Part 75.) In this case, it may be appropriate to require an initial verification of 

flowmeters and weigh scales and periodic calibration in accordance with the applicable industry 

standards or manufacturer directions. If the flowmeter manufacturer performed this verification 

at the flowmeter factory and did not recommend a second verification upon installation, the 

factory verification should suffice. Calibration of flowmeters and scales could be performed 

prior to the reporting year; after the initial calibration, recalibration could be performed as 

frequently as specified by the manufacturer. Under this approach, producers could perform the 

verification and calibration of their weigh scales during routine product line maintenance. 

For the gas chromatography analytical method described under the monitoring section of 

this document, monthly calibration, using known certified standards should be used. The 

calibration involves validating accurate measurement of these fluorocarbon standards across a 

range of possible concentrations, depending on which process streams are being measured. 

For development of process-vent-specific emission factors, facilities would need to 

conduct and meet the QA/QC procedures specified in the test methods used. 

6. Reporting and Recordkeeping Procedures 

To verify and document their emissions estimates, owners and operators of facilities 

producing fluorinated gases would report the following information, depending on their activities 

and on the estimation approach that they used. All facilities would report both their fluorinated 

GHG emissions and the quantities used to estimate them on a process-specific basis. They 

would also report the results of each initial scoping speciation, specifically, the chemical 

identities of the contents of potentially emitted streams. Facilities using the mass-balance 

approach would report the masses of the reactants, products, by-products, and wastes, and, if 

applicable, the quantities of any product in the by-products and/or wastes (if that product is 

emitted at the facility). They would also report the chemical identities of reactants, products, and 

by-products, along with the chemical equations used to estimate emissions. Facilities using the 

emission factor approach would report the activity data used to calculate emissions (e.g., the 

quantity produced, transformed, or destroyed) and the emission factors used to estimate them. 

Owners and operators would report annual totals of these quantities by process and facility. 

Where fluorinated GHG production facilities have estimated missing data, the facility 

would report the reason the data were missing, the length of time the data were missing, the 

method used to estimate the missing data, and the estimates of those data. 

52 
Maintaining records of the information used to determine the reported GHG emissions 

would enable us to verify that the GHG emissions monitoring and calculations were performed 

correctly. Owners and operators of facilities producing fluorinated GHGs would retain records 

documenting the data reported, including records of monthly emission estimation calculations, 

all data that went in to the calculations, calibration records for flowmeters, scales, and gas 

chromatographs, and documentation of emission factor development activities. 

53 
7. References 

3M 2009. Meeting Documentation for Telephone Calls on October 9 and November 12, 2009 

with 3M Representatives Regarding Fluorinated Gas Production. U.S. Environmental Protection 

Agency. 

Air Products 2009. Meeting Documentation for 17 November 2009 Telephone Call with Air 

Products Representatives Regarding Fluorinated Gas Production. RTI International. 

Arkema 2009. Meeting Documentation for Various Telephone Calls During Week of 7 October 

2009 with Arkema Representatives Regarding Fluorinated Gas Production. U.S. Environmental 

Protection Agency. 

DuPont 2009. Meeting Documentation for 13 November 2009 Telephone Call with DuPont 

Fluoropolymer Representatives Regarding Fluorinated Gas Production. RTI International. 

INEOS Fluor 2009. Meeting Documentation for October 2009 Telephone Calls with INEOS 

Fluor Representatives Regarding Fluorinated Gas Production. RTI International. 

3M Site Visit 2009. Documentation for October 2009 Site Visit to 3M Cordova, Illinois 

Regarding Fluorinated Gas Production. RTI International. 

DuPont Site Visit 2009. Documentation for October 2009 Site Visit to DuPont Corpus Christi, 

Texas Regarding Fluorinated Gas Production. RTI International. 

Centre Interprofessionnel Technique d’Etudes de la Pollution Atmospherique. Inventaire Des 

Emissions De Gaz A Effect De Serre En France Au Titre de la Convention Cadre Des Nations 

Unies Dur Les Changements Climatiques. Mars 2009. 

http://unfccc.int/files/national_reports/annex_i_ghg_inventories/national_inventories_submission

s/application/zip/fra_2009_nir_7apr.zip 

Daniela Romano, Chiara Arcarese, Antonella Bernetti, Antonio Caputo, Rocío D. Cóndor, Mario 

Contaldi, Riccardo De Lauretis, Eleonora Di Cristofaro, Sandro Federici, Andrea Gagna, Barbara 

Gonella, Riccardo Liburdi, Ernesto Taurino, Marina Vitullo. ISPRA - Institute for 

Environmental Protection and Research. Italian Greenhouse Gas Inventory 1990-2007. National 

Inventory Report, 2009. 

http://unfccc.int/files/national_reports/annex_i_ghg_inventories/national_inventories_submission

s/application/zip/ita_2009_nir_15apr.zip

EPA Office of Research and Development and Office of Solid Waste and Emergency Response 

of U.S. Environmental Protection Agency. Guidance on Setting Permit Conditions and Reporting 

Trial Burn Results Handbook, Volume II. EPA Publication No. EPA/625/6-89/019. January 

1989.http://www.epa.gov/nrmrl/pubs/625689019/625689019.pdf

EPA Office of Pollution Prevention Toxics and Syracuse Research Corporation (SRC). EPI Suite 

Version 4.00 January 2009. http://www.epa.gov/oppt/exposure/pubs/episuite.htm

54 
Flemish Environment Agency, Flemish Institute for Technological Research, Walloon Public 

Service, Brussels Institute for the Management of the Environment, Interregional Cell for the 

Environment, ECONOTEC. Belgium’s Greenhouse Gas Inventory (1990-2007). April 2009. 

http://unfccc.int/files/national_reports/annex_i_ghg_inventories/national_inventories_submission

s/application/zip/bel_2009_nir_15apr.zip

IPCC 2006, 2006 IPCC Guidelines for National Greenhouse Gas Inventories, Prepared by the 

National Greenhouse Gas Inventories Programme, Eggleston H.S., Buendia L., Miwa K., Ngara 

T. and Tanabe K. (eds). Published: IGES, Japan. Chapters 3, 6, 7 and 8. http://www.ipccnggip.iges.or.jp/public/2006gl/vol3.html 

IPCC 2006, 2006 IPCC Guidelines for National Greenhouse Gas Inventories, Prepared by the 

National Greenhouse Gas Inventories Programme, Eggleston H.S., Buendia L., Miwa K., Ngara 

T. and Tanabe K. (eds). Published: IGES, Japan. http://www.ipccnggip.iges.or.jp/public/2006gl/index.html

Memorandum from Schaffner, K. and Hancy, C., RTI International, to Ottinger, D., 

EPA/OAR/CCD. Threshold Analysis for Emissions, Promulgation of 40 CFR Part 98, subpart 

L, Fluorinated Greenhouse Gas Production. November 4, 2010. 

Tsang, W., Burgess Jr., D. R., and Babushok, V. (1998) “On the Incinerability of Highly 

Fluorinated Organic Compounds,” Combustion Science and Technology, 139:1, 385-402. 

Trenholm, A., Lee, C., and Jermyn, H. “Full-Scale POHC Incinerability Ranking and Surrogate 

Testing,” 17th Annual RREL Hazardous Waste Research Symposium, EPA Office of Research 

and Development, EPA/600/9-91/002 April, 1991, pp. 79-88. 

U.S. Environmental Protection Agency (EPA), “Developing a Reliable Fluorinated Greenhouse 

Gas (F-GHG) Destruction or Removal Efficiency (DRE) Measurement Method for Electronics 

Manufacturing: A Cooperative Evaluation with Qimonda,” March 2008, EPA 430-R-08-017. 

http://www.epa.gov/semiconductor-pfc/documents/qimonda_report.pdf 

U.S. Environmental Protection Agency (EPA), “Developing a Reliable Fluorinated Greenhouse 

Gas (F-GHG) Destruction or Removal Efficiency (DRE) Measurement Method for Electronics 

Manufacturing: A Cooperative Evaluation with IBM,” June 2009, EPA 430-R-10-004. 

http://www.epa.gov/semiconductor-pfc/documents/ibm_report.pdf 

U.S. Environmental Protection Agency (EPA), “Developing a Reliable Fluorinated Greenhouse 

Gas (F-GHG) Destruction or Removal Efficiency (DRE) Measurement Method for Electronics 

Manufacturing: A Cooperative Evaluation with NEC Electronics, Inc.,” December 2008, EPA 

430-R-10-005. http://www.epa.gov/semiconductor-pfc/documents/nec_report.pdf 

U.S. Environmental Protection Agency (EPA). Emission Inventory Improvement Program 

Volume II: Chapter 16. Methods for Estimating Air Emissions From Chemical Manufacturing 

Facilities. August 2007. www.epa.gov/ttn/chief/eiip/techreport/volume02/ii16_aug2007final.pdf

U.S. Environmental Protection Agency (EPA) Office of Air and Radiation and Office of 

Atmospheric Programs, Climate Change Division. Protocol for Measuring Destruction or 

55 
Removal Efficiency (DRE) of Fluorinated Greenhouse Gas Abatement Equipment in Electronics 

Manufacturing. March 2010. 

U.S. Environmental Protection Agency (EPA) Office of Air Quality Planning and Standards. 

Protocol for Equipment Leak Emission Estimates. EPA-453/R-95-017. November 1995. 

www.epa.gov/ttnchie1/efdocs/equiplks.pdf

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Services Inc.. Tracer Gas Protocol for the Determination of Volumetric Flow Rate Through the 

Ring Pipe of the Xact Multi-Metals Monitoring System. September 2006. 

www.epa.gov/ttnemc01/prelim/otm24.pdf

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Alternate Method (ALT-012)- An Alternate Procedure for Stack Gas Volumetric Flow Rate 

Determination (Tracer Gas). http://www.epa.gov/ttn/emc/approalt/alt-012.pdf

U.S. Environmental Protection Agency (EPA). Method 1- Sample and Velocity Traverses for 

Stationary Sources. http://www.epa.gov/ttnemc01/promgate/m-01.pdf

U.S. Environmental Protection Agency (EPA). Method 18 – Measurement of Gaseous Organic 

Compound Emissions by Gas Chromatography. http://www.epa.gov/ttnemc01/promgate/m18.pdf

U.S. Environmental Protection Agency (EPA). Method 205 - Verification of Gas Dilution 

Systems for Field Instrument Calibrations http://www.epa.gov/ttnemc01/promgate/m-205.pdf

U.S. Environmental Protection Agency (EPA). Method 21 – Determination of Volatile Organic 

Compound Leaks. http://www.epa.gov/ttnemc01/promgate/m-21.pdf

U.S. Environmental Protection Agency (EPA). Method 2A – Direct Measurement of Gas 

Volume Through Pipes and Small Ducts. http://www.epa.gov/ttnemc01/promgate/m-02a.pdf

U.S. Environmental Protection Agency (EPA). Method 2B- Determination of Exhaust Gas 

Volume Flow Rate from Gasoline Vapor Incinerators. 

http://www.epa.gov/ttnemc01/promgate/m-02b.pdf

U.S. Environmental Protection Agency (EPA). Method 2C- Determination of Gas Velocity and 

Volumetric Flow Rate in Small Stacks or Ducts (Standard Pitot Tube) 

http://www.epa.gov/ttnemc01/promgate/m-02c.pdf

U.S. Environmental Protection Agency (EPA). Method 2D – Measurement of Gas Volume Flow 

Rates in Small Pipes and Ducts. http://www.epa.gov/ttnemc01/promgate/m-02d.pdf

U.S. Environmental Protection Agency (EPA). Method 2F- Determination of Stack Gas 

Velocity and Volumetric Flow Rate With Three-Dimensional Probes. 

http://www.epa.gov/ttnemc01/promgate/Methd2F.pdf

56 
U.S. Environmental Protection Agency (EPA). Method 2G- Determination of Stack Gas Velocity 

and Volumetric Flow Rate With Two-Dimensional Probes. 

http://www.epa.gov/ttnemc01/promgate/Methd2G.pdf

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Measurement Methods from Various Waste Media. http://www.epa.gov/ttnemc01/promgate/m301.pdf

U.S. Environmental Protection Agency (EPA). Method 3B- Gas Analysis for the Determination 

of Emission Rate Correction Factor or Excess Air. http://www.epa.gov/ttnemc01/promgate/m03b.pdf

U.S. Environmental Protection Agency (EPA). Method 3-Gas Analysis for the Determination of 

Dry Molecular Weight. http://www.epa.gov/ttnemc01/promgate/m-03.pdf 

U.S. Environmental Protection Agency (EPA). Method 4 – Determination of Moisture Content 

in Stack Gases. http://www.epa.gov/ttnemc01/promgate/m-04.pdf

U.S. Environmental Protection Agency (EPA). Test Method 320- Measurement of Vapor Phase 

Organic and Inorganic Emissions by Extractive Fourier Transform Infrared (FTIR) 

Spectroscopy. http://www.epa.gov/ttnemc01/promgate/m-320.pdf

U.S. Environmental Protection Agency Center for Environmental Research Information, Office 

of Research and Development. Compendium Method TO-15- Determination Of Volatile 

Organic Compounds (VOCs) In Air Collected In Specially-Prepared Canisters and Analyzed By 

Gas Chromatography/ Mass Spectrometry (GC/MS). January 1999. 

www.epa.gov/ttnamti1/files/ambient/airtox/to-15r.pdf

U.S. Environmental Protection Agency Office of Air and Radiation. Technical Support 

Document for Emissions From Production of Fluorinated GHGs: Proposed Rule for Mandatory 

Reporting of Greenhouse Gas. February 2, 2009. 

57 
Appendix A. 

Mass Balance Approach: Equations from Re-Proposal TSD (March 22, 2010). 

58 
Appendix A 

Mass Balance Approach: Equations from Re-Proposal TSD (March 22, 2010). 

In the mass-balance approach, facilities weigh or meter the reactants fed into the process, 

the product resulting from the process, and any byproducts and wastes that are removed from the 

process (i.e., sent to the thermal oxidizer or other equipment, not immediately recycled back into 

the process). Facilities then calculate the difference between the mass of reactants fed into the 

process and the sum of the masses of the main product and those of any byproducts and/or 

wastes. This difference is then assigned to loss of reactants, loss of product, and/or conversion to 

byproducts. 

The following set of equations was included in the re-proposal TSD for the massbalancing method for estimating fluorinated GHG emission. 

The total mass of each fluorinated GHG product emitted annually from all fluorinated gas 

production processes would be estimated by using Equation L-5: 

∑∑ (Eq. L-5) ==

= i

Pip

p

EP E

11

mn

Where: 

EP = Total mass of each fluorinated GHG product emitted annually from all production 

processes (metric tons). 

EPip = Total mass of the fluorinated GHG product emitted from production process i over 

the period p (metric tons, defined in Equation L-7). 

n = Number of concentration and flow measurement periods for the year. 

m = Number of production processes. 

The total mass of fluorinated GHG by-product k emitted annually from all fluorinated gas 

production processes shall be estimated by using Equation L-6: 

∑∑ (Eq. L-6) ==

= i

Bkip

p

EBk E

11

n m

Where: 

EBk = Total mass of fluorinated GHG by-product k emitted annually from all production 

processes (metric tons). 

EBkip = Total mass of fluorinated GHG by-product k emitted from production process i over 

the period p (metric tons, defined in Equation L-8 on this section). 

n = Number of concentration and flow measurement periods for the year. 

m = Number of production processes. 

59 
The total mass of each fluorinated GHG product emitted from production process i over 

the period p would be estimated by calculating the difference between the expected production of 

the fluorinated GHG based on the consumption of one of the reactants (e.g., HF or a 

chlorofluorocarbon reactant) and the measured production of the fluorinated GHG, accounting 

for yield losses related to by-products and wastes. This calculation shall be performed using 

Equation L-7. 

( ) ∑∑= =

= −− −

k

Bkip

j

DjP

RR

PP

Pip LWCP

SCMW

SCMWR E

1 1

*

*

** q u

 (Eq.L-7) 

Where: 

EPip = Total mass of each fluorinated GHG product emitted from production process i over 

the period p (metric tons). 

P = Total mass of the fluorinated GHG produced by production process i over the period 

p (metric tons). 

R = Total mass of the reactant that is consumed by production process i over the period p 

(metric tons, defined in Equation L-8). 

MWR = Molecular weight of the reactant. 

MWP = Molecular weight of the fluorinated GHG produced. 

SCR = Stoichiometric coefficient of the reactant. 

SCP = Stoichiometric coefficient of the fluorinated GHG produced. 

cP = Concentration (mass fraction) of the fluorinated GHG product in stream j of 

destroyed wastes. If this concentration is only a trace concentration, cP is equal to 

zero. 

WDj = Mass of wastes removed from production process i in stream j and destroyed over the 

period p (metric tons, defined in Equation L-9). 

LBkip = Yield loss related to by-product k for production process i over the period p (metric 

tons, defined in Equation L-10). 

q = Number of waste streams destroyed in production process i. 

u = Number of by-products generated in production process i. 

The total mass of the reactant that is consumed by production process i over the period p 

shall be estimated by using Equation L-8: 

= − RRR RF (Eq. L-8) 

Where: 

R = Total mass of the reactant that is consumed by production process i over the period p 

(metric tons). 

RF = Total mass of the reactant that is fed into production process i over the period p 

(metric tons). 

RR = Total mass of the reactant that is permanently removed from production process i 

over the period p (metric tons). 

60 
The mass of wastes removed from production process i in stream j and destroyed over the 

period p would be estimated using Equation L-9: 

Dj = Fj

* DEWW (Eq. L-9) 

Where: 

WDj = The mass of wastes removed from production process i in stream j and destroyed over 

the period p (metric tons). 

WFj = The total mass of wastes removed from production process i in stream j and fed into 

the destruction device over the period p (metric tons). 

DE = Destruction Efficiency of the destruction device (fraction). 

Yield loss related to by-product k for production process i over period p would be 

estimated using Equation L-10: 

( )

( ) Bk P

kip P Bk

Bkip MEMW

L

* = ** MEMWB

 (Eq. L-10) 

Where: 

LBkip = Yield loss related to by-product k for production process i over the period p (metric 

tons). 

Bkip = Mass of by-product k generated by production process i over the period p (metric 

tons, defined in Equation L-11). 

MWP = Molecular weight of the fluorinated GHG produced. 

MWBk = Molecular weight of by-product k. 

MEBk = Moles of the element shared by the reactant, product, and by-product k per mole of 

by-product k. 

MEP = Moles of the element shared by the reactant, product, and by-product k per mole of 

the product. 

If by-product k is responsible for yield loss in production process i and occurs in any 

process stream in more than trace concentrations, the mass of by-product k generated by 

production process i over the period p would be estimated using Equation L-11: 

= ∑ (Eq. L-11) 

j

kip

* ScB jBjk

q

Where: 

Bkip = Mass of by-product k generated by production process i over the period p (metric 

tons). 

61 
cBkj = Concentration (mass fraction) of the by-product k in stream j of production process i 

over the period p. If this concentration is only a trace concentration, cBkj is equal to 

zero. 

Sj = Mass flow of process stream j of production process i over the period p. 

q = Number of streams in production process i. 

If by-product k is responsible for yield loss, is a fluorinated GHG, occurs in any process 

stream in more than trace concentrations, and is not completely recaptured or completely 

destroyed; the total mass of by-product k emitted from production process i over the period p 

would be estimated using Equation L-12: 

∑∑ (Eq. L-12) = =

−= −

l

Dj RlBkl

j

Bkip kip Bkj ScWcBE

1 1

* *

q x

Where: 

EBkip = Mass of by-product k emitted from production process i over the period p (metric 

tons). 

Bkip = Mass of by-product k generated by production process i over the period p (metric 

tons). 

cBkj = Concentration (mass fraction) of the by-product k in stream j of destroyed wastes 

over the period p. If this concentration is only a trace concentration, cBj is equal to 

zero. 

WDj = The mass of wastes that are removed from production process i in stream j and that 

are destroyed over the period p (metric tons, defined in Equation L-9). 

cBkl = The concentration (mass fraction) of the by-product k in stream l of recaptured 

material over the period p. If this concentration is only a trace concentration, cBkl is 

equal to zero. 

SRl = The mass of materials that are removed from production process i in stream l and that 

are recaptured over the period p. 

q = Number of waste streams destroyed in production process i. 

x = Number of streams recaptured in production process i. 

Choice of Reactant Whose Yield Is Measured. 

EPA has considered use of one reactant to estimate emissions under the mass-balance 

approach (rather than both as originally proposed). Some fluorinated GHG producers have noted 

that, for various reasons, it is sometimes considerably more difficult to track the yields of some 

reactants than others (e.g., HF vs. an organic feedstock). EPA notes that facilities estimating 

their emissions based on the yield of one reactant would still need to be able to demonstrate that 

their estimate met the statistical error test that might be required. 

If an alternate reactant was measured, it would be necessary for facilities to be extremely 

thorough in the monitoring approach and calculations in order to account for all potential 

emissions. The reactant whose yield is measured and its relationship to fluorinated GHG 

62 
63 

emissions for a particular process must be fully analyzed to ensure that it provided an accurate 

representation of the emissions.