EPA Contract No. EP-D-11-006 Work Assignment 5-09 

# DRAFT

Technical Support Document

Optical Gas Imaging Protocol
(40 CFR Part 60, Appendix K)

Prepared for:



## Jason DeWees U.S. Environmental Protection Agency

Office of Air Quality Planning Standards Air Quality Assessment Division Measurement Technology Group (E141-03) Research Triangle Park, NC 27711

Prepared by:



## Tracey L. Footer Eastern Research Group, Inc. 601 Keystone Park Drive, Suite 700

Morrisville, NC 27560

Revision No. 5 August 11, 2015ii 

### DISCLAIMER

This document and related appendices are currently in draft f ormat. Do not cite or quote. This document will continue to be developed based on the latest information. This draft report has been initially reviewed by the U.S. Environmental Protect ion Agency’s (EPA’s) Office of Air Quality Planning and Standards and has been approved in draft fo rm.

Mention of or referral to commercial products or service s and/or links to non-EPA websites does not imply official EPA endorsement of or responsibilit y for opinions, ideas, data, or products presented at those locations, or guarantee the validity of the information provided. Mention of commercial products/services and non-EPA websites is provi ded solely as a reference to information on topics related to environmental protection that may be useful to EPA staff and the public.iii



### ABSTRACT

This technical support document (TSD) provides background, technic al analyses, experimental results, and other supplemental information to support regulat ory development of an optical gas imaging (OGI) protocol. OGI technology can be used to detec t fugitive emissions of compounds such as methane and volatile organic compounds from industria l sources, including those within the refinery, oil and gas, and chemical sectors. The pote ntial use of OGI technology has been presented in two Federal Register notices (77 FR 76248, June 18, 2012 and 79 FR 36880, June 30, 2014). A protocol for applying OGI technology will be codifie d at 40 CFR part 60, appendix K. This document presents a comprehensive regulatory histor y and results of a literature review on the technology development and observations of current application of OGI technology. The literature review identifies the technology, applicatio ns, and limitations of the current remote measurement and monitoring technologies. This TSD also con tains the results from multiple efforts commissioned by the U.S. Environmental Protectio n Agency (EPA) for Eastern Research Group, Inc. (ERG) to perform laboratory studies, evaluat e OGI technology, and research potential operations and procedures for detecting leaks using OGI technology. Laboratory studies include testing of the spectral limitations and gas sensiti vity and determining the effect of various environmental factors on leak detection. Finally, the append ices of this document contain supplemental information to the laboratory studies.iv 

### TABLE OF CONTENTS

Section Page No.

ABSTRACT ..........................................

................................................... ................................ iii

I. BACKGROUND ........................................

................................................... ..................1
A. Leak Detection and Repair .........................

................................................... ..............1
B. Purpose and Scope of this Document...................

................................................... .....2

II. POLICY AND REGULATIONS ............................

................................................... ......3
A. History of LDAR Based on the 1990 CAA Amendments .... ........................................3
B. Regulatory Status .................................

................................................... ....................6
C. Costing Evaluations ..............................

................................................... ................. 11

III. LITERATURE REVIEW .................................

................................................... .......... 12
A. Technology ......................................

................................................... ...................... 12 1. History .........................................

................................................... ..................... 12 2. Basis of OGI technology ..........................

................................................... ......... 13 3. Available Technology ..............................

................................................... ......... 16
B. Observations and Improvements ....................

................................................... ........ 17 1. Initial OGI Technology Performance Studies .......... ............................................. 17

2. API Follow-on Studies 5,74,75



### .................................................. ............................... 21 3. ETV Minimum Detection Limit Study .................. ............................................... 24 4. Attempts at Calibration and Performance Verification .......................................... 27 5. Studies to Compare OGI Technology to Method 21 ...... ....................................... 35 6. Studies Comparing OGI Technology to “Bagging” Techniques.... ........................ 36

C. Conclusion .......................................

................................................... ...................... 38

D. References and Reviewed Literature .................

................................................... ..... 41

IV. ERG LABORATORY EVALUATIONS ........................ ............................................... 49
A. Feasibility and Detection Limit Study .............

................................................... ....... 50
B. Spectral Limitations and Gas Sensitivity Studies ..

................................................... .. 58

C. Assessment of Parameters that Influence Plume Char acteristics/Detection ................ 66
D. Camera Field Operation ............................

................................................... ............. 72

V. SUMMARY ...........................................

................................................... .................... 77

VI. LIST OF APPENDICES AND SUPPLEMENTAL DOCUMENTS ..... .......................... 80v 

### LIST OF TABLES

Table 2-1. Timeline of Major Regulatory Milestones Leadi ng to Current Status ..........................4
Table 2-2. Federal Regulations Requiring LDAR Programs with Method 21 Leak Monitoring 22,

119



### .................................................. ................................................... ......................4
Table 3-1. Currently Commercially Available Handheld OGI Ca mera Systems ......................... 17
Table 3-2. Average Minimum Detection Level Mass Emissio n Rates (g/hr), Number of

Measurements in Parentheses 24



### .................................................. ........................... 19
Table 3-3. Summary of Controlled Laboratory Testing Minimum Detection Limits (g/hr) at
Various Wind Speeds 74



### .................................................. ....................................... 22
Table 3-4. Summary of Controlled Laboratory Minimum Detec tion Limits (g/hr) for Pure Gases

at Various Wind Speeds 74



### .................................................. ................................... 23
Table 3-5. Summary of Controlled Laboratory Minimum Detec tion Limits (g/hr) for Gases

Diluted with N 2 

### at Various Wind Speeds 74



### .................................................. .......... 23
Tables 3-6 and 3-7. MDLRs for Pure Compounds at Different Win d Speeds and Gas Mixtures at

Different Wind Speeds 5,75



### .................................................. ................................... 24
Table 3-8. Summary of MDLs and % Agreement with a M21 Monito ring Device during Lab

Testing 10,11



### .................................................. ................................................... ....... 26
Table 3-9. Empirical Methane NECL Values for a FLIR GF320 OGI Camera 88 

### ........................ 34
Table 3-10. Comparison of Field-Derived Values to Published Labo ratory Detection Limits

(g/hr) 35



### .................................................. ................................................... ............. 37
Table 3-11. Comparison Between FLIR GF320 and Opgal EyeCGas Spec ifications 33,73 

### ............ 38
Table 3-12. Minimum Detected Leak Rates (MDLRs) for the FL IR GF320 per manufacturer 33 

### . 40
Table 4-1. Results from Feasibility Study at About 20,000 ppmV (2%) Total Hydrocarbons

(50/50 Propane-Butane Mix) ...............................

.................................................. 53
Table 4-2. Results from Feasibility Study at About 10,000 ppmV (1%) Total Hydrocarbons

(50/50 Propane-Butane Mix) ...............................

.................................................. 54
Table 4-3. Results from Feasibility Study at About 5,000 ppmV (0.5%) Total Hydrocarbons

(50/50 Propane-Butane Mix) ...............................

.................................................. 54
Table 4-4. Results from Feasibility Study at About 500 ppmV T otal Hydrocarbons .................. 54
Table 4-5. Results from Feasibility Study Holding Mass Em ission Rate Equal to 10 g/hr with

OGI Camera Thermal Tuning on Auto (50/50 Propane-Butane Mix) ..................... 55
Table 4-6. Results from Feasibility Study at About 500 ppmV T otal Hydrocarbons on High

Sensitivity Mode (50/50 Propane-Butane Mix) .............. ....................................... 55
Table 4-7. Results from Feasibility Study at About 500 ppmV T otal Hydrocarbons on High

Sensitivity Mode, Rerun (50/50 Propane-Butane Mix) ........ .................................. 56
Table 4-8. Overall Results from the Feasibility Study S howing Both ∆ T Conditions ................. 56
Table 4-9. OGI Cameras Evaluated for Spectral Limitations and Gas Sensitivity....................... 59
Table 4-10. FLIR GF320 Spectral Window Results ..............

................................................... .. 62
Table 4-11. Integrated Spectral Absorbance and Propane Relati ve Response Factors ................ 63vi



### Table 4-12. Repeat Feasibility Study Run 1 (2% concentration) with FLIR and Opgal OGI

Cameras ...........................................

................................................... .................. 66
Table 4-13. Repeat Feasibility Study Run 3 (5000 ppmV) with FLIR and Opgal OGI Cameras . 67
Table 4-14. Repeat Feasibility Study Run 4 (500 ppmV) with FLI R and Opgal OGI Cameras ... 67
Table 4-15. Repeat Feasibility Study Run 5 (10.2 g/hr held cons tant) with FLIR and Opgal OGI

Cameras ...........................................

................................................... .................. 68
Table 4-16. Rerun of Repeat Feasibility Study Run 5 .........

................................................... .... 68
Table 4-17. Repeat Feasibility Study Run 10 (500 ppmV on High Se nsitivity/Enhanced Modes)

with FLIR and Opgal OGI Cameras ...................... ................................................ 68
Table 4-18. Repeat of Feasibility Study Run 5 with FLIR and O pgal on High

Sensitivity/Enhanced Mode .............................

................................................... ... 69

Table 4-19. Horizontal Wind Shear, Normal/Auto Mode ........

................................................... 69
Table 4-20. Horizontal Wind Shear, High Sensitivity/Enhanced M ode ...................................... 69
Table 4-21. Reynolds Number Study Results with 2” Orifice

................................................... . 70
Table 4-22. Reynolds Number Study Results with 1” Orifice

................................................... . 70
Table 4-23. Reynolds Number Study Results with 1/2” Orifice

................................................. 70
Table 4-24. Reynolds Number Study Results with 1/4” Orifice

................................................. 71
Table 4-25. Reynolds Number Study Results with 1/8” Orifice

................................................. 71
Table 4-26. Reynolds Number Study Results with 1/8” Orifice and High/Enhanced Sensitivity

Modes ..............................................

................................................... .................. 71
Table 4-27. List of LSP Leaking Elements ................

................................................... ............. 74
Table 4-28. Initial Experimental Matrix for Blind Surveys

................................................... ..... 74
Table 4-29. List of OGI Camera Operators and Experience Lev el ............................................. 75
Table 4-30. Overall Blind Survey Results for Leaks Released a t 2% Concentration ................... 76vii 

### LIST OF FIGURES

Figure 2-1. Distribution of the Total Equipment Counts and E stimated Emissions by Screening

Range 1



### .................................................. ................................................... ...............8
Figure 3-1. Basic Principle of IMSS Diffractive Optics 45



### ................................................... ........ 15
Figure 3-2. Correlation Between the Concentration Measure ments Made by the FID Device as

Compared to that Using the Sherlock ® 

### VOC 47



### .................................................. .... 16
Figure 3-3. Field Survey Performance Summary of Infrared Cam eras 24 

### ..................................... 20
Figure 3-4. MDLRs Versus Standoff Distance for Three Lens es 5 

### .............................................. 22
Figure 3-5. Calibration Chambered Vessel 6



### .................................................. ............................. 28
Figure 3-6. Gas Imaging IR Camera Verification and Calibra tion System 131 

### ............................. 29
Figure 3-7. Quality Control Chart for IR Camera Daily Ch eck 131 

### .............................................. 29
Figure 3-8. Example of a Cluster of Δ I vs. Δ T Curves for Different PPM-M Levels of Benzene 131



### .................................................. ................................................... ........................ 30
Figure 3-9. Example of a Δ I vs. Concentration-Path Length Curve 131 

### ........................................ 30
Figure 3-10. Experimental Set Up of Gas Cells with Contro lled Blackbody Sources 7 

### ................ 31
Figure 3-11. Measurement of the Signal Attenuation from 2,000 ppm of Methane 7 

### ................... 31
Figure 3-12. Signal Attenuation vs. Gas Concentration 7



### .................................................. .......... 32
Figure 3-13. NECL Measurement Set Up 88



### .................................................. ............................. 33
Figure 3-14. Signal Intensity as a Function of CL 88



### .................................................. ................. 33
Figure 4-1. CLGS Gas Blending Component Developed by ERG for Preliminary Performance

Tests .............................................

................................................... ..................... 51
Figure 4-2. Overview of CLGS in Place at ERG’s Laborator y ................................................. .. 52
Figure 4-3. Feasibility Study Results by Flow Rate and Mass Emission Rate for Measurements in

Manual and Auto Modes ..................................

................................................... .. 57
Figure 4-4. EPA ORD Custom-built Spectral Test Platform .

................................................... .. 58
Figure 4-5. Example Placement of Neutral Density Filters f or Non-Thermometric IR Spectral
Tests in the Visible (Left) and IR (Right) .........

................................................... .. 59
Figure 4-6. A FLIR GasFindIR Mounted and Aligned to the Monoch romator Exit Slit.............. 60
Figure 4-7. The Exit Slit of the Monochromator as Imaged by the FLIR GF320 ........................ 60
Figure 4-8. Average Spectral Window Curve for FLIR GF320 Camera s ................................... 61
Figure 4-9. Average FLIR GF320 Spectral Window Curve Illustratin g POL Locations ............. 62
Figure 4-10. Example Gas Sensitivity Curve for 50/50 Propane-Buta ne Mixture ....................... 65
Figure 4-11. Overview of Reynolds Number Data .............

................................................... ..... 72
Figure 4-12. Custom-built LSP by ERG from the Front (left) and Side (right) Showing Leak

Locations .........................................

................................................... .................. 73
Figure 5-1. Concept Diagram of OGI Camera Performance Enve lope ....................................... 78
Figure 5-2. Concept Diagram of the OGI Camera Performance Envelope in the Presence of NonIdeal Conditions ....................................

................................................... ............. 79viii 

### LIST OF ACRONYMS

Å Ångström (0.0001 μ m) AIMM approved instrument monitoring method

API American Petroleum Institute AQCC State of Colorado Air Quality Control Commission AWMA Air and Waste Management Association

AWP Alternative Work Practice BAGI backscatter absorption gas imaging

CAA Clean Air Act

CAAA Clean Air Act Amendments of 1990 C-H carbon-hydrogen CLGS custom controlled leak generation system DI&M directed inspection and maintenance DIAL/LIDAR differential absorption light detection an d ranging systems ELP enhanced LDAR program EPA U.S. Environmental Protection Agency ERG Eastern Research Group, Inc. ETV Environmental Technology Verification program

FID flame-ionization detector FIP federal implementation plan FTIR Fourier transform infrared spectroscopy

FOV field-of-view FPA focal plan array

ft feet

GF GasFindIR g/hr grams per hour GHG greenhouse gas GIT Gas Imaging Technologies, LLC GWP global warming potential HAP hazardous air pollutant HC hydrocarbon HgCdTe mercury cadmium telluride IMSS image multi-spectral sensing

InSb indium antimonide

IR infrared lbs pounds LDAR leak detection and repair LSI Leak Surveys, Inc. LSP leak simulation platform

MDL minimum detection limit

MDLR minimum detected leak rate

mK millikelvin NECL noise equivalent concentration length NEIC National Enforcement Investigations Center NESHAP national emission standards for hazardous air po llutantsix



### NETD noise equivalent temperature difference NSPS new source performance standards OGI optical gas imaging OP-FTIR open-path Fourier transform infrared spectroscopy OP-TDL open-path tunable diode laser ORD Office of Research and Development ORS optical remote sensing PAT Pacific Advanced Technology PIA pixel intensity analyzer PID photo-ionization detector POL point of limitation PNNL Pacific Northwest National Laboratory ppm parts per million ppm•m parts per million – meters ppmv parts per million by volume RPM radial plume mapping RRF relative response factor

SF 6 

### sulfur hexafluoride SIP state implementation plan SOCMI synthetic organic chemicals manufacturing industry TSD technical support document UV-DOAS ultraviolet differential optical absorption spe ctrometer VOC volatile organic compound

μ m micrometer1



### I. BACKGROUND

Fugitive emissions are a significant source of air emis sions in the United States. The U.S. Environmental Protection Agency (EPA) defines fugitive emis sions as emissions that could not reasonably pass through a stack, chimney, vent, or other fu nctionally-equivalent opening. Examples of fugitive emissions include methane or volat ile organic compounds (VOCs) from chemical plants or oil refineries, particulate emissio ns from handling solid raw materials in chemical or other manufacturing, or evaporative emission s of VOCs from wastewater treatment.

The magnitude of fugitive emissions can be significant fo r a source category. For example, at chemical processing plants, one study showed that about ha lf of all hydrocarbon emissions typically stem from fugitive emissions from equipment. 35 

### An emissions inventory of four natural gas processing plants showed that more than 80% of methane emissions resulted from fugitive equipment leaks. 17 

### Emissions from the oil and gas industry, specifically fr om production, transmission, storage, and distribution, are currently among the largest anthropogenic sources of

U.S. methane emissions. 129 

### In 2013, methane emissions from natural gas systems and pet roleum

systems a 

### were 157.4 and 25.2 million metric tons of carbon dioxide e quivalents, respectively, representing 69% of methane emissions from the energy se ctor. Fugitive methane emissions from compressors, including compressor seals, are the pri mary emission source from natural gas processing. 49 

### In emission projections to 2018, fugitive emissions contin ue to be the largest emission source category for the oil and gas sector. 49 

### For the purposes of this document, fugitive emissions are the unplanned losses of gaseous compounds fro m pipes, valves, flanges, and other types of industrial equipment.

A. Leak Detection and Repair

Leak detection and repair (LDAR) programs are standardized regulatory work practices that are designed to reduce fugitive emissions of air pollutants fro m industry by identifying leaking equipment for repair. 119 

### Regulatory LDAR programs first appeared in EPA regulation s in 1983 and continue today. Regulatory LDAR programs typically inv olve several elements: an inventory of equipment that could be leaking; monitoring the equipmen t to determine if there is a leak (as defined by the applicable regulation) using sensory monitoring (i.e., audio, visual, olfactory) or EPA Method 21, and performing corrective action on equipme nt that is found to be leaking. EPA Method 21 (Determination of Volatile Organic Compound Leaks) is the most common method for identifying leaking equipment. Method 21 monitoring require s the use of a portable

instrument to detect VOC leaks above a certain action level from equipment such as valves, flanges, pressure relief devices, pump seals, compressor s eals, agitator seals, connectors, openended lines, sampling connections, and other common industri al connections at individual

sources.

In 2008, the EPA introduced the Alternative Work Practice ( AWP) as an option to replace standard work practices that use only Method 21 monitoring. T he AWP allows LDAR programs the flexibility to implement OGI techniques for screening in lieu of Method 21. Instead of using a portable instrument to detect and measure the concentrati on of VOC leaks using a

a IPCC source category 1B2a (onshore and offshore crude oil production, transportation, and refining operations).2



### photoionization detector (PID) or flame ionization detect or (FID), OGI technology utilizes an infrared (IR) camera to make equipment leaks visual by m eans of thermographic imaging.

Because OGI technology continues to evolve and improve, the EPA is conducting research into the current state of OGI technology to help standardiz e its use for regulatory purposes. The potential use of OGI technology has been presented in t wo Federal Register notices (National Uniform Emission Standards for Storage Vessel and Transfer Operations, Equipment Leaks, and Closed Vent Systems and Control Devices at 77 FR 76248, June 18, 2012; and Petroleum Refinery Sector Risk and Technology Review and New Source Performance Standards at 79 FR 36880, June 30, 2014). A protocol for applying OGI technology will be c odified at 40 CFR part 60, appendix K.

B. Purpose and Scope of this Document

The purpose of this document is to provide technical background information on OGI. Information presented in this document will help the EPA in developing, evaluating, and promoting standardized prescriptive procedures for source ch aracterization and compliance monitoring related to the use of OGI technology to detect fugitive gas emissions of VOCs, hazardous air pollutants (HAPs), and greenhouse gases (GHGs) (i.e., methane, sulfur hexafluoride) from industrial environments.

Since the formation of the EPA in 1970, the issue of man agement and mitigation of the fugitive

emissions from industrial activities to ambient air has received a lot of attention because of fugitive emissions’ direct effect on human health an d the environment. This document reviews the evolution of federal regulations designed to control t he amount of fugitive HAPs and VOCs released by leaking industrial equipment up to the current im plementation of LDAR programs and the recent increase in use of OGI technology to as sist these programs. The information presented in this document includes a review of publically ava ilable literature. This document focuses on the theory and performance of OGI technology application for LDAR programs and presents results from controlled laboratory studies aim ed at characterizing the performance of OGI technology for leak detection.

Following are the main organizational compartments of this document:

• Section II – A summary of the regulatory history that co vers regulatory and policy development up to today.

• Section III – A technical literature review that discuss es commercially available OGI technologies and associated studies.

• Section IV – Research commissioned by the EPA for ERG to evaluate technology performance and methods related to the application of OGI for leak detection.

• Section V – Summary and observations.

• Section VI – Appendices and supporting documents.3



### II. POLICY AND REGULATIONS

A. History of LDAR Based on the 1990 CAA Amendments

Coincident with the formation of the EPA in 1970, Congres s passed the Clean Air Act (CAA), which required the EPA to develop national ambient air qual ity standards (NAAQS) and establish measurement methods for criteria pollutants. A dditionally, in response to the CAA’s directive to establish federal standards of performance for new sources within categories of sources contributing significantly to air pollution, the E PA launched the new source performance standards (NSPS) program. The intention of the NSPS pro gram is to control emissions from new, modified, or reconstructed stationary sources by settin g standards that limit emissions through the use of the best system of emission reduction, which takes into account the cost of achieving such reductions. Existing sources were regulated through state implementation plans (SIPs) or the federal implementation plan (FIP).

Federal leak standards were first introduced when the NSP S for synthetic organic chemicals manufacturing industries (SOCMI) and petroleum refineries were promulgated in October 1983 and May 1984, respectively. These actions required monitoring of specific types of equipment in

VOC or HAP service b 

### , depending on the regulation, using EPA Method 21 or other equi valent monitoring. The types of industrial equipment targeted in these actions included pumps, valves, compressors, pressure relief devices, sampling connection s ystems, open-ended lines, flanges, and other connector types. 118 

### Along with the first leak standards, Method 21 was first promulgated in 1983 at 40 CFR part 60, appendix A.

During the first two decades after being founded, the EPA be gan to investigate the level of

hazard associated with individual HAPs that were listed in the CAA and developed a list of stationary sources that emitted these HAPs. The EPA de veloped national emission standards for hazardous air pollutants (NESHAP) to reduce, by the maximum degree, the emissions of HAPs from these source categories.

With the rise of new environmental issues getting public att ention (e.g., inability to control HAP emissions from industrial sources, continued NAAQS non- attainment, increased emissions from automobiles, and acid rain), Congress passed the reauthoriz ation of the CAA complete with over 600 additional pages of amendments, known as the Clean Air Act Amendments of 1990 (1990 CAAA). 103 

### Following passage of the 1990 CAAA, the EPA developed a new s trategy for addressing HAP issues that involved shifting the focus from i ndividual HAPs to source categories that may emit multiple pollutants. 102 

### This shift in regulatory approach resulted in the addition of source-specific NESHAPs based on Maximum Achi evable Control Technology (MACT). MACT standards aim to reduce HAP emissions from stationary sources by requiring

all sources to reduce their emissions to the levels of e missions achieved by the best performing sources in a source category. In 1990, with the introductio n of the 1990 CAAA, Method 21 was

revised to its current form.

b In VOC or HAP service means that the equipment is expecte d to come into contact with and/or contain a liquid or gas with VOC or HAP, generally above a specific level (e.g. , greater than 10% by weight). The definition of in VOC or HAP service varies by regulation.4



### The control of fugitive emissions (and, therefore, LDAR programs) is mostly implemented through these two major regulatory programs today: the NSP S and NESHAP programs. Table 2- 1 lists the major regulatory milestones that shaped curr ent LDAR programs and requirements. Table 2-2 lists the federal regulations that require a for mal LDAR program as of 2015.

Table 2-1. Timeline of Major Regulatory Milestones Leading to Cu rrent Status

Year Common Name Document

1955 Air Pollution Control Act Public La w 84

- 159

1963 Clean Air Act (CAA) Public Law 88

- 206

1967 Air Quality Act Public Law 90

- 148

1970 National Environmental Policy Act ( N EPA) Public Law 91

- 190

1970 Clean Air Act of 1970 (1970 CAA) Public Law 91

- 604

1983 NSPS LDAR and Method 21 Promulgatio n 48 FR 37598

1984 NESHAP (Part 61) LDAR Promulgation 49 FR 23513

1990 CAA amendments extend LDAR provisions to NESHAP

MACT; (1990 Clean Air Act Amendments (CAAA)) 55 FR 25602, Public Law 101-549

2000 Consolidated Federal Air Rule (CAR) for Equipment Le aks 65 FR 78268

2008 Alternative Work Practice (AWP) Promulgation 73 FR 78199 (40 CFR 60.18, 63.11, and 65.7)

2008 Greenhouse Gas Reporting Rule 74 FR 56260

2011 Proposed Uniform Standards for Equipment Leaks 77 FR 36248 (40 CFR 65)



### Table 2-2. Federal Regulations Requiring LDAR Programs with Method 21 Leak Monitoring 22, 119

40 CFR Part and Subpart Regulation Title

Part 60 Standards for Performance of New Stationary Sources ( NSPS)

Subpart VV Standards of Performance for Equipment Leaks of VOC in t he Synthetic Organic Chemicals Manufacturing Industry for which Construction, Reconstruc tion, or Modification Commenced After January 5, 1981, and on or Before November 7, 2006

VVa Standards of Performance for Equipment Leaks of VOC in t he Synthetic Organic Chemicals Manufacturing Industry for Which Construction, Reconstr uction, or Modification Commenced After November 7, 2006

XX Standards of Performance for Bulk Gasoline Terminals

DDD Standards of Performance for Volatile Organic Compound (VO C) Emission s from the

Polymer Manufacturing Industry

GGG Standards of Performance for Equipment Leaks of VOC in P etroleum Refineries for which

Construction, Reconstruction, or Modification Commenced After January 4, 1983, and on or Before November 7, 2006

GGGa S tandards of Performance for Equipment Leaks of VOC in Pe troleum Refineries for Which

Construction, Reconstruction, or Modification Commenced After November 7, 2006

KKK Standards of Performance for Equipment Leaks of VOC Fro m Onshore Natural Gas

Processing Plants for Which Construction, Reconstructio n, or Modification Commenced After January 20, 1984, and on or Before August 23, 20115



### Table 2-2. Federal Regulations Requiring LDAR Programs with Method 21 Leak Monitoring 22, 119

40 CFR Part and Subpart Regulation Title

QQQ Standards of Performance for VOC Emissions From Petr oleum Refinery Wastewater

Systems

Part 61 National Emissions Stan dards for Hazardous Air Pollutants (NESHAP)

Subpart F National Emission Standard for Vinyl Chloride

J National Emission Standard for Equipment Leaks (Fugitive Emi ssion Sources) of Benzene

L National Emission Standard for Benzene Emissions from Co ke By

- Product Recovery Plants

V National Emission Standard for Equipment Leaks (Fugitive Emi ssion Sources)

BB National Emission Standard for Benzene Emissions From Be nzene Transfer Operations

FF National Emission Standard for Benzene Waste Operations

Par t 63 NESHAP for Source Categories

– Maximum Achievable Control Technology (MACT)

Subpart H National Emission Standards for Organic Hazardous Air Pollutants for Equipment Leaks

I National Emission Standards for Organic Hazardous Air Pol lutants for Certai n Processes

Subject to the Negotiated Regulation for Equipment Leaks

J National Emission Standards for Organic Hazardous Air Pol lutants for Polyvinyl Chloride

and Copolymers Production

R National Emission Standards for Gasoline Distribution Facilities (Bulk Gasoline Terminals

and Pipeline Breakout Stations)

S National Emission Standards for Hazardous Air Pollutants from the Pulp and Paper Industry

U National Emission Standards for Hazardous Air Pollutants E missions: Group I Polymers and

Resins

W N ational Emission Standards for Hazardous Air Pollutants fo r Epoxy Resins Production and

Non-Nylon Polyamides Production

Y National Emission Standards for Marine Tank Vessel Loading O perations

CC National Emission Standards for Hazardous Air Pollutants from Petroleum Refineries

DD National Emission Standards for Hazardous Air Pollutants from Off

- Site Waste and Recovery Operations

GG National Emission Standards for Aerospace Manufacturing and Rework Facilities

HH National Emission Standards for Haza rdous Air Pollutants from Oil and Natural Gas

Production Facilities

OO National Emission Standards for Tanks

– Level 1

PP National Emission Standards for Containers

QQ National Emission Standards for Surface Impoundments

SS National Emission Standa rds for Closed Vent Systems, Control Devices, Recovery Devices, and Routing to a Fuel Gas System or a Process

TT National Emission Standards for Equipment Leaks

– Control Level 1

UU National Emission Standards for Equipment Leaks

– Control Level 2

WW National Emission Standards for Storage Vessels (Tanks)

– Control Level 2

XX National Emission Standards for Ethylene Manufacturing Process Units: Heat Exchange

Systems and Waste Operations

YY National Emission Standards for Hazardous Air Pollutants f or Source Categories: Generic Maximum Achievable Control Technology Standards6



### Table 2-2. Federal Regulations Requiring LDAR Programs with Method 21 Leak Monitoring 22, 119

40 CFR Part and Subpart Regulation Title

GGG National Emission Standards for Pharmaceuticals Production

HHH National Emission Standards for Hazardous Air Pollutants from Natural Gas Transmission

and Storage Facilities

III National Emission Standards for Hazardous Air Pollutants for Flexible Polyurethane Foam

Production

JJJ National Emission Standards for Hazardous Air Pollutant Emissions: Group IV Polymers and

Resins

MMM National Emission Standards for Hazardou s Air Pollutant s for Pesticide Active Ingredient

Production

OOO National Emission Standards for Hazardous Air Pollutant Emissions: Manufacture of

Amino/Phenolic Resins

PPP National Emission Standards for Hazardous Air Pollutant Emissions for Polyether Polyols

Production

VVV National Emission Standards for Hazardous Air Pollutants: Publicly Owned Treatment

Works

EEEE National Emission Standards for Hazardous Air Pollutants: Organic Liquids Distribution

(Non-Gasoline)

FFFF National Emission Standar ds for Hazardous Air Pollutants: Miscellaneous Organic Chemical

Manufacturing

BBBBB National Emission Standards for Hazardous Air Pollutants for Semiconductor Manufacturing

GGGGG National Emission Standards for Hazardous Air Pollutants: Site Remediatio n

HHHHH National Emission Standards for Hazardous Air Pollutants: Miscellaneous Coating

Manufacturing

BBBBBB National Emission Standards for Hazardous Air Pollutants f or Source Category : Gasoline Distribution Bulk Terminals, Bulk Plants, and Pipeline Faci lities

VVVVVV Hazardous Air Pollutants for Chemical Manufacturing Area S ources

Part 65 Consolidated Federal Air Rule

Subpart F Equipment Leaks

Part 98 Mandatory Greenhouse Gas Reporting Program

Subpart W Petroleum and Natural Gas Systems

Part 264 Standards for Owners and Operators of Hazardous Waste T reatment, Storage, and Disposal

Facilities

Subpart BB Air Emission Standards for Equipment Leaks

Part 265 Interim Status Standards for Owners and Operators of Hazar dous Waste Treatment, Storage, and Disposal Facilities

BB Air Emission Standards for Equipment Leaks



### B. Regulatory Status

Both the EPA and industry encountered unexpected challenges in implementing LDAR programs with Method 21 following initial establishment of t he LDAR programs listed in7



### Table 2-2. EPA Method 21 involves positioning an instrument probe near the source of a potential equipment leak and measuring the VOC concentratio n as the probe is judiciously (and slowly) scanned around the potential leak source. A formal LDAR program requires that the facility maintain an inventory of all equipment at th e facility subject to the regulation, complete with unique equipment IDs, leak definition, monitoring frequen cy information, and previous screening and repair results. If the survey result for an individual piece of equipment is above the regulatory leak definition, then the equipment is consid ered to be leaking and must be repaired and rescreened within a prescribed time frame. With indiv idual facilities easily having thousands of pieces of equipment to monitor, this process immedia tely becomes a heavy resource burden to industries seeking compliance.

The following paragraphs present some of the challenges an d findings of implementing LDAR programs using Method 21.

1993. Methane is a potent GHG that is estimated to have 28-36 t imes more global warming potential (GWP) than carbon dioxide on a 100-year time fra me. 51 

### The overall threat of increasing GHG emissions to hasten global climate chan ge compelled President Clinton to announce the Climate Change Action Plan of 1993. As a part of this plan, the EPA created the Natural Gas STAR program in 1993 to increase the aware ness of methane emission sources and to serve as a platform for sharing emissions reduction innovations and best practices throughout the oil and natural gas industry. 25 

### The primary goal of the Gas STAR program is to offer a voluntary, flexible, and cost-effe ctive partnership between the government and the oil and natural gas industry. By volunteer ing to become a partner of the program, companies exchange information with the EPA and, in turn, the EPA provides news, updates, and regular transfer of information meetin gs to assist their facilities with emissions reduction in all areas of operations, includi ng those that were not regulated.

1995. Around this time, the term “Directed Inspection and Mai ntenance” (DI&M) started to appear in the literature relative to cost-effective str ategies implemented by the facilities to proactively find and fix leaks. DI&M was one of the rec ommended practices introduced to industry in 1995 through the Gas STAR program. Industry began to r ealize that reducing fugitive emissions also meant reducing product loss and the refore could lead to improved economic performance. With a highly profitable product that was difficult to contain, the oil and natural gas industry was particularly interested in ho w to prevent methane product loss. However, not all companies willingly signed up for the Gas STAR program, and simply implementing the DI&M programs did not necessarily ensure that a facility using the practice was in compliance with all regulatory emissions control requirements. (DI&M does not satisfy the requirements for regulatory LDAR programs.)

1997. In 1997, the American Petroleum Institute (API) commis sioned a study to investigate the possibility for conducting LDAR surveys in a more eff icient manner. 1 

### This study collected data from seven Los Angeles, California refine ries over 5.5 years for a total of 11.5 million refinery equipment measurements. Results showe d that valve equipment in gas and light liquid service combined contributed an average of 68% of the total facility fugitive VOC emissions, while connectors in the same service co ntributed only 28% of the total facility fugitive VOC emissions, but were three times as abundant as valves by count of equipment monitored. A major discovery from this study wa s that 92% of the controllable8



### fugitive emissions (non-zero screening values) were attributed to just 0.13% of the total equipment monitored

(as represented by Figure 2-1), and the study conc luded that the current leak detection practice spends about 98% of the LDA R program’s effort monitoring nonleakers. The study went on to propose that a more c ost effective method for LDAR program compliance should focus more on the high emission r ate leakers and avoid performing EPA Method 21 monitoring on all equipment types during every survey.

Figure 2-1. Distribution of the Total Equipment Cou nts and Estimated Emissions by Screening Range 1



### 1997-1999. By 1999, it was obvious to the EPA that industry compliance reports were not matching up with results from comparison monitoring conducted by the EPA’s National Enforcement Investigations Center (NEIC). 110 

### For example, 17 facilities were monitored during investigations by NEIC for several years, an d while the average leak rate reported by facilities to the EPA was 1.3%, the NEIC found the average leak rate to be 5.0%. A potential explanation for this discrepancy appeared in a 1997 report by the Bay Area Air Quality Management District, whose findings showed that a o ne centimeter difference in analyzer position equated to a 57% chance of missing an actu al leak. 110 

### This amount of sensitivity to operator error while performing Method 21, and the resulting under-reporting of potentially 80 million pounds of VOCs being emitted annually, f ueled action by the EPA to find new ways to quickly and definitively identify significa nt leaks.9



### 1999. Starting around 1999, to address poor performing LDAR programs, th e Department of Justice teamed up with the EPA to issue civil penalties an d consent decrees to industry LDAR programs that were found to be deficient. The consen t decrees instructed the penalized facility to implement a stricter program of l eak detection and repair monitoring

called “Enhanced LDAR.” 22,62 

### Enhanced LDAR programs (ELPs) go above and beyond regulatory LDAR requirements to systematically improve t he performance of a facility’s LDAR program. ELPs include tighter restrictions and/or mo re activity in subsections such as: documentation, monitoring frequency, LDAR action levels, r epairs, delay of repairs, equipment upgrades, training, LDAR audits, recordkeeping, and r eporting. 62 

### ELPs have

resulted in considerable emissions reductions at individual facilities. 97



### 2002-2005. Clearstone Engineering conducted two studies (in 2000 17 

### and 2004-2005 18 

### ) that evaluated the potential for methane emissions reduction an d cost-saving opportunities at gas processing facilities. In both studies, Clearstone found t hat fugitive equipment leaks contributed the majority of methane and non-methane hydro carbon emissions and that, of the fugitive equipment leak emission categories, equipment t hat is associated with vibrational and heat-cycle services contributed a large majority of the total fugitive emissions. A significant result of the 2002 Clearstone report was tha t an estimated 94.9% of total natural gas losses would be cost-effective to reduce. However, similar to f indings of the 1997 API study 1



### , 

### both Clearstone studies found that only a small percenta ge (2.4% of all the equipment surveyed) under hydrocarbon service were determined to be le aking, in this case using a leak definition of 10,000 parts per million by volume (ppmv). The Clearstone studies also prompted the Gas Technology Institute (GTI, formerly kno wn as the Gas Research Institute, GRI) to petition the EPA for acceptance of alternative work practices to Method 21 as early

as 2000. 17



### The 2002 Clearstone study also indicated that using a HiFlow TM 

### Sampler could provide more

accurate estimates of actual leak rates versus Method 21. The HiFlow TM 

### Sampler was developed by GTI as an economic means of estimating the emission rate from individual leaking equipment components with sufficient accuracy to allow an objectiv e cost-benefit analysis of each repair opportunity. Leak source emission rate is the product of the measured pollutant concentration and the measured leak flow rate. Emission rates, as oppo sed to actual pollutant concentrations, provide an assessment of the severity of the leak in ter ms of air mass volume and time, which can in turn be used to determine long and short term exposure . In addition to tools such as the

HiFlow TM 

### Sampler, a more accurate way to determine the mass em ission rate of fugitive gases from equipment leak sources is through “bagging c 

### ” or physical isolation techniques. 116 

### However, this technique is estimated to cost roughly $500 per equipment com ponent; and with facilities having as many as a million components, this technique is im practical and prohibitively expensive.

c Bagging is a method to measure the emission rate from an equipment component by isolating the component from ambient air to collect any leaking compound(s). A tent (i.e ., bag) made of material impermeable to the compound(s) of interest is constructed around the leak int erface of the piece of equipment. More information on bagging can be found in Section 4 of the EPA’s Protocol for Equipment Leak Emission Estimates (http://www.epa.gov/ttn/chief/efdocs/equiplks.pdf).10



### EPA studies have correlated Method 21 concentration measur ement values with a mass emissions rate from available bagging data as a way to e stimate mass emissions rates for whole

facilities. 116 

### However, because current OGI technology cannot reliably measure gas concentration values, a more resource intensive method such as EPA Method 21, bagging, or radial plume mapping with Fourier Transform Infrared Spect roscopy/Tunable Diode Laser/ Differential Optical Absorption Spectrometer (FTIR/TDL /DOAS) would still be required to estimate facility emission rates. 115



### Following the Clearstone report in 2002, 17 

### Natural Gas STAR began to publish “Lessons

Learned” documents as technical references. Natural Gas STAR industry partners evaluated the effectiveness of DI&M programs to cut total facility emissions while also reducing facility costs. The projected cost curves from the Cle arstone 2002 study indicated the likelihood that industry could make choices that would resul t in financial improvement with the added benefit of reducing fugitive emissions to the atmos phere, which appealed to state and federal regulators. Since 2002, the Natural Gas STAR progr am has published 19 Lessons Learned, covering sources such as compressors, dehydrators, and pneumatics and controls. The Lessons Learned serve as comprehensive guides for impl ementing methane emission reduction technologies and practices and summarize cost a nd benefit information.

2006-2007. Furry et al., 2006; Reese et al., 2007 and Trefiak, 2006 report ed for industry on LDAR applications and technology challenges. These repor ts all agree that the implementation of Method 21 is timely and expensive, while advancing technologies offer promise to streamline and reduce the cost of routine monit oring. 35,80,98 

### A paper by Robinson et al. in 2007 found that using OGI technology to assist the periodic screening procedures increases the survey rate of equipment dramatically from about 60 pieces of equipment per hour with Method 21 to over 2,000 pieces of equipment per hour with OGI technology and that OGI technology-assisted surveys identified 97% of t he total mass emissions detected from leaking sources with Method 21. 85 

### These studies provided evidence that using OGI technology to assist LDAR programs with their regular e quipment surveys promises to be a quicker and more cost-effective method of identifying the l argest sources of leaking

emissions relative to Method 21 and will increase the amo unt of total facility fugitive emissions reduction because OGI technology can identify fugitive emissions from all equipment categories, regardless of whether that equip ment is mandated for LDAR program compliance or not.

Grievances from industry, in addition to information on the difficulties of using Method 21, led to the proposal and ultimate promulgation of the AWP in 2008. The AWP, also commonly known as “Smart LDAR,” gives LDAR programs the flexibil ity to implement OGI techniques for equipment screening in lieu of Method 21. Industry’s initi al response to the proposal of the

AWP was favorable and even enthusiastic. 68,80,98 

### However, due to concerns raised during the proposal of the AWP about whether OGI technology could detect persistent low-leaking equipment, the EPA included an annual Method 21 survey require ment in the AWP, with a statement that this requirement would be revisited as peo ple began to use the AWP and more information on OGI technology became available. This res ulted in a lack of interest by industry to utilize the AWP in lieu of standard LDAR monitoring. Nonetheless, the promulgation of the AWP in 2008 was a catalyst for a flurry of studies and publi cations on its implementation. 10,11,68,7811



### On March 26, 2012, the EPA proposed a set of emission standa rds for storage vessels and transfer operations, equipment leaks, and closed vent s ystems and control devices known as the “Uniform Standards” in an effort to ensure consistency and streamline recordkeeping and reporting requirements for facilities with sources subject to multiple regulations. 48,127 

### The requirements proposed in the Uniform Standards would be appli cable only when referenced by a specific NESHAP or NSPS. As part of the Uniform Standar ds, the EPA proposed to allow the use of OGI technology in lieu of Method 21, as long as use of OGI technology followed the requirements of the protocol for use of OGI technology in 40 CFR 60, Appendix K, which has not yet been developed. The EPA recognized the potential in OGI technology for streamlining compliance activities related to emissions control, but because there is a well-documented need for OGI technology performance and operational studies, 94 

### the EPA still needed more data before concrete specifications could be outlined. The EPA received numerous comments on the proposal, but has not yet finalized the Uniform Standards.

States may opt to set emission standards that are more stringent than those required by the EPA. One such example is the enactment of Colorado’s Air Qua lity Control Commission (AQCC) Regulation Number 7 in 2014, which covers the oil and natural gas sectors. This rule allows owners or operators to use one of the Approved Instrument M onitoring Method (AIMM), such as Method 21, OGI technology or any other Division approved instr ument based monitoring device

or method. 21 

### Some of the more progressive requirements included into Regulation 7 include:

• Provisions to reduce methane emissions from oil and gas dev elopment (first state in the nation to address methane);

• Increased control and inspection requirements for storage tanks (first standard in the U.S. to require tank emissions are captured and routed to control devices);

• Added requirement for well production facilities to connect their gas streams to a pipeline or control device from the first date of production;

• More stringent control requirements for glycol dehydrators ;

• Extended the LDAR program requirements to include open-ended va lves and lines; and

• Specifies the requirement of the use of best management practices (including increased use/allowance for OGI camera application and comprehens ive recordkeeping and reporting) for well maintenance.

Colorado’s Regulation 7 requirements prescribe LDAR progr am schedules according to threshold emission rates (in tons per year). This indi cates that at least one LDAR screening survey is conducted via Method 21 or comparable quantification m ethod. Thereafter, facilities are allowed to use AIMMs, such as OGI cameras, for LDA R surveys.

C. Costing Evaluations

[This section will discuss the results from studies pe rformed on the financial burden and projected savings in relation to fugitive leak emissions r eduction activities.]12



### III. LITERATURE REVIEW

ERG searched the literature to identify the technology, applications, and limitations of the current remote measurement and monitoring technologies. Thi s section presents the findings of

the literature search.

A. Technology

1. History

Remote measurement and monitoring technologies have been a vailable since the 1970s and extensive efforts have been made to make these technologie s more widely acceptable to the monitoring community. 4,15,65,86,108,124 

### In late 2011, the EPA published the Optical Remote Sensing (ORS) for Measurement and Monitoring of Emissions F lux handbook, 71 

### which lists some of the more prominent technologies and application s, including:

• Ultraviolet Differential Optical Absorption Spectromete r (UV-DOAS)

• Open-Path Fourier Transform Infrared Spectroscopy (OP-FTI R)

• Raman spectroscopy

• Tunable Diode Laser (OP-TDL)

• Differential Absorption Light Detection and Ranging Sy stems (DIAL/LIDAR)

• OTM-10 d



### /Radial Plume Mapping (RPM)

• Eddy Covariance Flux

• Optical Gas Imaging (OGI).

The application of some of these technologies has bee n difficult, especially with respect to LDAR programs. Roadblocks include: high cost, complex measure ment theory, need for highly specialized operators, difficulty-of-use, identification of leak location, and inconsistent units of measure for data output to the end-user (e.g., parts per mil lion – meters (ppm·m), path-averaged concentration). 124



### The scope of the literature search was broad initially, but ERG focused on leak detection technologies based on IR imaging (both active and passi ve) due to the potential for these technologies to reduce the time, labor, and cost of equ ipment monitoring for LDAR program compliance. 129 

### Of these technologies, the EPA selected only OGI came ras for implementation for the AWP. Other technologies were not selected bec ause of the reasons above, in addition to

technical limitations and interferences. 68 

### In-depth discussion on the different ORS technologies and their strengths, weaknesses, and applications can be found in the EPA ORS handbook 124

d OTM-10 is “Other Test Method 10 – Optical Remote Sensi ng for Emission Characterization from Non-Point Sources” that contains various configurations of radial plume mapping or RPM. It is available from the EPA at http://www.epa.gov/ttn/emc/prelim.html.13



### 2. Basis of OGI technology

OGI cameras produce images of gaseous emissions using one of two different IR sensing approaches: active or passive IR imaging. Active IR imagi ng provides the IR light source via controlled laser output to the environment that is then reflected off the background and attenuated or absorbed as it encounters gas species along the optical path. Passive IR imaging uses available IR radiation (anything with a temperature—abo ve 0 K—produces IR radiation) to detect differences in the IR intensity between backgro und IR and gas plume IR radiation. The type of gas species that will be imaged is a function of the spectral transmission window in the camera design. For example, many common OGI cameras f or VOC detection have a bandpass

filter that allows transmission of the 3.2 to 3.4 micro meter ( μ m) spectral region to the detector. This spectral region is characteristic of the stretchi ng vibrational energy between a carbonhydrogen (C-H) bond and is typically targeted when trying to detect or measure gases containing alkanes, alkenes, aromatics, and other hydrocarbons (such as methane, benzene, propane, butane and many others). 92 

### OGI cameras with bandpass filters that allow the tran smission of different spectral windows can target different gas types; such as 4. 52 – 4.67 μ m for carbon monoxide,

10.3 – 10.7 μ m for sulfur hexafluoride and anhydrous ammonia, and 8.0 – 8.6 μ m for refrigerant

gases. 34



### Active IR Imaging

Backscatter Absorption Gas Imaging (BAGI) cameras produce a live image by illuminating the viewing area with infrared laser light and detecting the a mount of reflected (or backscattered) laser light returned to the instrument’s detector. When the laser light of a specified wavelength is strongly absorbed by a gas, a shadowy cloud of that gas be comes visible as a darkened area in the live image. 84 

### This method of hydrocarbon gas leak detection works indepen dently of ambient conditions but is limited by the laser wavelength output spe cified. Active IR imagers that use carbon dioxide lasers for their light source are unable to illuminate some target hydrocarbons

such as methane. Sandia National Laboratories has deve loped two BAGI cameras to address the laser wavelength limitations: one for petroleum refiner ies, and one for the natural gas industry (to detect methane).

For the BAGI technology to image a leak there must be some sort of reflective surface close

behind the leak. 84,85 

### A leak cannot be imaged against the sky or a distant bac kground because the

camera detector will not receive sufficient backscatt ered light intensity. As of 2007, BAGI

cameras from Sandia National Laboratories and Laser I maging Systems weighed between 20 and 30 pounds and could only run about 1 to 1.5 hours on battery power. 84,85 

### Quantification is not yet available with this technology and eye-safety for surro unding personnel is a concern due to laser

output.

Passive IR Imaging

Due to the power demands and optical complexity of using co ntrolled light sources with active IR imaging, manufacturers of OGI cameras will more com monly turn to passive IR imaging techniques to develop a more market viable system. Passive IR imaging cameras typically comprise an IR-transmissive lens, a staring focal plan e array (FPA) detector, a cooling system,14



### and a processing system. 8,64 

### The selection of the FPA depends on the wavelength reg ion of

interest.

For detection of hydrocarbons, the region of interest i s typically 3 – 5 μm, for which a detector made of indium antimonide (InSb) is the FPA of choice. However, in order to generate an image of sufficient contrast between gas plumes and the appar ent background, passive IR imagers need stricter controls on the spectral bandwidth of the ima ge and a reduction of signal noise. To address noise reduction in OGI detectors, a cooling module ( like a Stirling engine) is incorporated into the camera design to cool the detector.

Recently there has been research and developments using microbolometer detectors which have resulted in products (such as Bertin Technologies’ Second Sight 9 

### ) now being commercially available. Microbolometer detectors do not need to be cry o-cooled; however, the physics behind the thermal conductivity response mechanism of microbolom eter-based devices renders them slower and less sensitive than cooled photo-detection devi ces, like InSb FPAs. 50



### Two very different techniques have evolved to control the spectral bandwidth of passive IR imagers, band-pass filter and diffractive optics. Opgal an d FLIR Systems, Inc. have each developed their own offering of an IR camera (the EyeCGa s and GasFindIR 320 (GF320), respectively) based on OGI technology that restricts b andwidth to 3.2 – 3.4 μm. This bandwidth is spectrally harmonious with major absorption lines i n the spectra of many target gases as

mentioned above. 26 

### Because of the lack of complexity with this type of cam era design, it is smaller, easier to use, and more robust.

Another way to control the spectral bandwidth is through methods called hyperspectral and multispectral imaging. Recent advances of this technology have increased the number of potential OGI instruments for leak detection application s since the start of this effort by the EPA to evaluate all commercially available OGI technology sys tems. Some of these upcoming instruments are not yet ready for commercial distributi on and/or are so new that performance studies are either still underway or have yet to be plann ed. As this document is currently still in draft form, more analysis will be incorporated as newe r OGI technology systems and relevant study data becomes available.

Gas Imaging Technologies, LLC (GIT) has developed the She rlock ® 

### VOC OGI camera, which uses diffractive optics and multispectral image processi ng to image, speciate, and quantify fugitive gas emissions. The Sherlock ® 

### VOC camera operates based on the principles of image multi-spectral sensing (IMSS). IMSS is a form of diffr active optics whereby the incident light being received through the camera lens is both imaged and dis persed using a combination of a diffractive imaging spectrometer and an adaptive tunable fi lter. 40,42,43,44,45,46 

### Similar to a monochromator, where light is separated spectrally and t he light that passes through the exit slit is scanned, with IMSS the light is spectrally dispersed using an optical lens that can be focused along the optical axis to produce images of narrow spectral bands that are measured sequentially in time on the FPA detector. See Figure 3-1 for an examp le of the basic concept of IMSS compared to a monochromator.15



### Figure 3-1. Basic Principle of IMSS Diffractive Optics 45



### The camera operator of a Sherlock ® 

### VOC has full control on the motion of the optical l ens, allowing the operator to scan a series of wavelengths or dwell indefinitely on one wavelength. 46


### The result is a frame-by-frame imaging of different spec tral wavelengths that can be selected and combined with visual images to show gas leaks as false colo r. By selecting to visualize different wavelengths, it is possible to distinguish between gas spec ies with the Sherlock ® 

### VOC; however, the exact identification and quantification of gas conc entration procedures utilized by the associated software has not yet been evaluated in this document because it is proprietary. Declaring that the Sherlock ® 

### VOC can quantify gas concentrations comes with a heavy caveat as verification studies by an external party has not yet been performed and Q A evaluations on any measured gas concentrations produced by the Sherlock ® 

### VOC still need to be carefully studied.

US Patent # 6680778 46 

### for the Sherlock ® 

### “Gas Leak Detector” states this technology determines concentrations of the target chemical by calculating the absorption (or emission) of the target chemical at its absorption (or emission) wavelength t hrough the gas plume and comparing this value to absorption amounts at the same wavelength meas ured simultaneously from a background (out-of-plume) region. In a presentation at t he 99 th 

### annual meeting of the Air and Waste Management Association (AWMA), Hinnrichs et al. 47 

### explained further that the log of the ratio of the signal intensity from the gas and the ba ckground is equal to the product of the absorption coefficient of the gas, the path length of t he gas, and the concentration of the gas, as illustrated in the equation below. The plume depth (or pat h length) is determined by assuming the gas plume is symmetric and using the 2D pixel footprint of the image of the gas. 47

### −  

 

###  
 

###  = 	

The quantification of gas concentration by the Sherlock ® 

### VOC was compared with results from a FID at an oil and gas plant in Viggiano, Italy. 47 

### The study did not find many leaking equipment detected by EPA Method 21, and so the comparison was limite d to six measurements. Of these six measurements, three had concentrations higher than the FID saturation level, and one was taken during rain, which interfered with the FID detection . The study claimed that the two remaining measurements agreed well, providing Figure 3-2 as evide nce of good correlation. Where the FID measured 3,300 ppm, the Sherlock ® 

### VOC measured 4,530 ppm. And where the FID measured 9,155 ppm, the Sherlock ® 

### VOC measured 9,060 ppm. These measurements equate 

## Monochromator IMSS16



### to a relative percent difference of 31% and 1%, respectivel y. Added in the conclusions of this study is a statement regarding the need for more testing t o better understand the accuracy of the

Sherlock ® 

### VOC’s gas concentration quantification performance. 47



### Figure 3-2. Correlation Between the Concentration Measurement s Made by the FID Device as Compared to that Using the Sherlock ® 

### VOC 47



### Gas-imaging devices based on OGI technology operate by visua lly representing the temperature profile in a field of view where a gas cloud has a differ ent thermal signature than its apparent background. The difference between the temperature of a ta rgeted gas cloud and the temperature of the apparent background for that gas cloud is known as “del ta-T” ( ∆ T). This is an important property to understand with respect to OGI technology because the greater the difference in temperature between the gas cloud and its apparent background ( or the larger the absolute value

of ∆ T becomes), the higher the contrast between the two obj ects will appear in the OGI technology display and the more likely it will be for that leak to be detected by the OGI technology operator or automated display algorithm.

3. Available Technology

Both FLIR and GIT have long-wave IR options for imaging gases such as sulfur hexafluoride (SF 6 

### ) and ammonia (NH 3 

### ). As current LDAR activities focus principally on gases that absorb in the mid-wave IR (3 – 5 μ m), so does this review. Commercially available OGI sy stems that operate in the mid-wave IR are displayed in Table 3-1 wit h estimated purchase costs, safety certifications, notes on the detector technology, and w hether the manufacturer offers capability to quantify gas concentration (via software) or not.17



### Table 3-1. Currently Commercially Available Handheld OGI Camera Systems

Model Make Est. Cost Intrinsically

Safe? Detector

Technology Quant?

GF320 FLIR $85 ,000 No InSb No

EyeCGas O pgal $86,500 Yes HgCdTe No

Sherlock

®

VOC Gas Imaging

Technology $100,000 No Diffractive w/

InSb Yes*

* The ability of the Sherlock ® VOC to consistently provide a quantification value for ga s concentration has not been sufficiently evaluated or verified. 41



### The allowance for the application of OGI cameras in r egulatory LDAR programs through the AWP was partly to help alleviate the time, labor, and fi nancial cost of compliance for industry and partly to help improve the rule effectiveness of LDAR programs. In order for the technology to meet these objectives, it must be able to consisten tly visualize target compound leaks at concentrations equal to the leak definition as specified by the applicable regulation. It also must be field portable so that an LDAR inspector can comfortabl y use the OGI technology for the duration of the LDAR survey without interruption for power (battery life), data (space), or physical demands (not too heavy or bulky). Ideally, the te chnology would be easy to deploy with minimal training and staffing requirements, have a reasona ble cost for initial purchase and maintenance, and not endanger the OGI operators (be int rinsically safe in hazardous environments). The technology must be rugged enough for routin e field use and provide a near real-time response with the capability of identifying the exact source of the leak.

Other potential units, such as Bertin Technologies’ Sec ond Sight TC and Telops Hyper-Cam have been excluded from this list due to the impractical w eight and size of the units for LDAR application. 9,53,63 

### The Sherlock ® 

### VOC has also been determined impractical for LDAR applications by the EPA for similar reasons. 127 

### However, the Environmental Technology Verification (ETV) program did perform similar performa nce assessments on the FLIR

GasFindIR TM 

### MW (the predecessor to the FLIR GF320) and Sherlock ® 

### VOC cameras which demonstrated that the minimum detection limits (MDLs) f or the Sherlock ® 

### VOC were generally higher and that the FLIR GasFindIR TM 

### MW performed better overall. Results from these ETV assessments are provided in Table 3-2 and described in the ne xt section. 10,11



### B. Observations and Improvements

Because of the importance proper leak identification and r epair ultimately has on human health, safety, and the environment, many studies have been conducte d to try and delineate the expected technology performance, limitations, and best practice s associated with performing leak detection surveys using OGI cameras. This section presents summaries of key efforts at evaluating detection limit performance, operational cond itions, and emission rate estimates.

1. Initial OGI Technology Performance Studies

After an intensive air quality study in Texas in 2000 reve aled a discrepancy between aerial measurements of chemical species concentrations in th e atmosphere over the Houston-Galveston area and what investigators expected the chemical species concentrations to be based on18



### available VOC emission inventory estimates, the Texas Commission on Environmental Quality (TCEQ) focused its efforts on better characterizing fug itive emissions through the development

of additional leak detection and evaluation methods and us ing these new methods and conventional methods to update emissions factors and corr elation equations. 24 

### The TCEQ funded studies to conduct evaluations of OGI technology to assis t leak detection surveys at chemical and petroleum facilities. The ENVIRON International Corp oration (Environ) was appointed by the Texas Council on Environmental Technology (TCET, which wa s later absorbed into TCEQ) in

June 2003 to conduct the first of these studies.

TCEQ/Environ Study 24



### The main objectives for Environ in this study were to co nduct a laboratory evaluation on OGI technology and to conduct a field evaluation on OGI tech nology for the development of a monitoring protocol using OGI technology for leak detection and updated emission factors and/or correlation equations. 24 

### Four OGI technology-based IR cameras were evaluated in the laboratory:

• Pacific Advanced Technology’s (PAT) IMSS passive IR ima ging camera (the predecessor to GIT’s Sherlock ® 

### VOC)

• Laser Imaging Systems’ Long-wave BAGI active IR imaging c amera

• Sandia National Laboratory’s Mid-wave BAGI active IR i maging camera

• Leak Survey, Inc.’s (LSI) Hawk passive IR imaging camera (the predecessor to FLIR’s GasFindIR and GF320 cameras).

The tests were performed at the BP laboratory in Napervi lle, IL as detailed in the Environ report. The experimental set up that resulted from this effort was later used to conduct further OGI technology performance evaluations described later in t his document. 5,10,11,74,75



### Delta-T ( ∆ T)

The TCEQ/Environ study employed a copper plate background pain ted flat black to assess the ability for PAT’s IMSS and LSI’s Hawk OGI cameras to det ect gases as the ∆ T approaches zero. Under controlled laboratory conditions, they found that both cameras were able to detect 60 grams per hour (g/hr) butane test gas with a ∆ T as little as 0.5°C. 24 

### This result prompted the investigators to conclude that the ∆ T parameter was not crucial in OGI technology leak detec tion as the OGI technology instruments were sensitive enough to be able to visualize gas leaks with very small ∆ T values.

Laboratory Minimum Detection Limit Tests

The TCEQ/Environ study evaluated the minimum detectable m ass emission rates of the four OGI cameras under controlled laboratory conditions fo r the following gas species of interest: ethylene, 1,3-butadiene, 1-butene, and propylene. Butane gas wa s also tested where time and

resources allowed. All four OGI cameras were able to dete ct all test gases at mass emission rates less than 60 g/hr except the Mid-wave BAGI camera could not detect 1,3-butadiene and butane test gas was not evaluated for the Long-wave BAGI OGI ca mera. Table 3-2 summarizes the19



### results for each OGI camera under low wind conditions with a concrete background at a distance of 10 feet (ft) from the leak source.

Table 3-2. Average Minimum Detection Level Mass Emission Rates (g/hr), Number of

Measurements in Parentheses 24

OGI Camera Ethylene 1,3-Butadiene 1-Butene Propylene Butane

PAT’s IMSS 36 (3) 27 (3) 18 (3) 25 (4) 15 (3)*

Long

- Wave

BAGI 6 (5) 19 (3) 28 (3) 24 (3) Not Tested

Mid

- Wave

BAGI 21 (3) Not Detected Below 60 g/hr 8 (3) 17 (4) 1 (3)

LSI Hawk 14 (3) 18 (2) 5 (5) 7 (3) 5 (5)

* Results are uncertain and expected to be biased high due t o a leak in the gas delivery system that was discovered after testing.



### Other parameters expected to affect the leak detection c apability of OGI cameras were tested during the TCEQ/Environ study. Two different backgrounds were employed to simulate various industrial conditions: concrete wall and metal gas cylinder s (to represent metallic background equipment). Two different wind speeds were evaluated: low wind speeds (between 0 and 2 mph) and high wind speeds (between 3 and 5 mph). The leaking sourc e was imaged at two distances (10 ft and 20 ft) to evaluate the impact distance from leak s ource had on leak detection capability.

To investigate the impact of a reflective background, the TCEQ/Environ study used metal cylinders as an experimental background. The results indica te that the “darker” areas of the metal cylinders prevented plume detection in those areas, but did not impact the overall minimum detection limits for any of the OGI cameras tested as the movement of the test gas plume was still visible in the “lighter” areas of the metal cy linder background. However, preliminary study data indicate that there is an impact on the minimum detection limit capabilities for each OGI camera by the other conditions tested (namely, higher wind speeds and farther distances from the leak source).

In February 2004, Environ carried out the field portion of a s tudy on the performance of different OGI camera technologies. 24 

### This field study found that none of the four OGI camera technologies tested or Method 21, alone or in combinatio n, detected all gas leaks. A total of 66 leaks were found at two study locations, representing norm al industrial conditions for leaks of ethylene, propylene, butenes, 1,3-butadiene, and hexanes. The four OGI cameras found 31 of the 66 leaks (47%), and Method 21 found 49 of the 66 leaks (74%). Noneth eless, OGI camera surveys detected 533.9 g/hr of the overall 595.4 g/hr mass emis sions found by Method 21 and measured by bagging, or about 90%, and indicate that the OGI cameras captured the majority of the larger leaks. Figure 3-3 is a graphical representation of the leaks seen or unseen by each OGI technology over the measured mass emission rate determ ined by bagging. 2420



### Figure 3-3. Field Survey Performance Summary of Infrared Cam eras 24



### The y-axis in Figure 3-3 is unitless, the black X data points represent the leak rates of leaks discovered via Method 21 but not detected by the OGI cameras, and the hollow data points represent a bagged leak that was not detected by the camera . Of the OGI camera technologies tested, passive IR (the LSI Hawk, predecessor to the FL IR and Opgal OGI cameras) detected the lowest mass emission leak (1.4 g/hr), detected the most leaks, detected all leaks above the Method 21 equivalency leak rate e 

### of 60 g/hr, and detected all leaks larger than 21 g/hr. 24 

### The other camera technologies tested missed leaks either ne ar or above the Method 21 equivalency leak rate of 60 g/hr. The IMSS camera (i.e., Sherlock ® 

### VOC) detected leaks that could not be verified with Method 21, these were labeled as “False Po sitives” and are depicted on the left side of Figure 3-3 in the zero region. 24 

### According to this study—based on the OGI camera technologies available at the time of the study and the compounds detected—cameras designed with passive IR OGI technology are the most practicable and reliable for leak detection surveys.

Because LDAR applicable OGI cameras alone are not yet able to quantify the concentration or mass emission rates of fugitive gas emissions, and beca use there is still some concern remaining over OGI detection of very small leaks, other detection technologies may be useful when combined with AWP surveys. For example, a PID is a highly sensitive hand held device that can be extremely useful when coupled into an AWP program. 90 

### However, a PID will measure only gas concentrations and not direct mass emission rates, thereby, still requiring the application of correlation equations to calculate whole facility leak m ass emission rates as with the current

e Common Method 21 leak definitions of 500, 1,000, and 10,000 ppmv are employed by various LDAR program regulations to ensure a specific level of environmental protection from fugitive emissions. Monte Carlo analys is has been extensively studied as a way to determine the le ak rate level that would result in an equivalent level of environmental protection when OGI technology is used in l ieu of Method 21. For the purposes of AWP implementation, the EPA approved an equivalency leak rate of 60 g/hr when monitoring is performed on a bimonthly frequency. 10921



### work practice of Method 21. However, at the time of public ation, the results of the TCEQ study gained OGI technology favorable attention from industry f or its cost, size, weight, portability, performance, user-friendliness, and value as a potential t ool to assist AWP leak detection

surveys. 74



### 2. API Follow-on Studies 5,74,75



### One year after the TCEQ/Environ study, the API sponsor ed continuation studies using the same laboratory facility in Naperville, IL to evaluate two new er OGI cameras: the FLIR GasFindIR, and the PAT Sherlock. Studies by Panek 74,75 

### and Benson 5 

### report on the results from these followon efforts.

Operational conditions such as lens focal length, gas te mperature, background composition, steam presence, wind speed, and gas mixture versus pure compo und were evaluated as possible convoluting factors when establishing new detection limits for FLIR GF-series OGI

cameras. 5,74,75



### • The focal length of the lens did affect the detection c apability of the camera. Using the same lens but increasing the distance to the target resu lted in increased detection limits. Conversely, higher focal length lenses had better detect ion limits compared to shorter focal length lenses at the same distance. 5,75 

### Minimum detected leak rates (MDLRs) were plotted versus standoff distance in Figure 3-4 to illustrat e this effect.

• Adding to the efforts of the earlier TCEQ study, Panek 75 

### found that an increase in the gas temperature increased the visible contrast of the gas pl ume against a uniform background (by increasing the temperature differential between the gas a nd the background) and lead

to a reduction of detection limits. 75



### • The detection limits for imaging gas against a background of metal cylinders were higher than those with a uniform concrete background. It is assum ed that this is because of a lack of thermal contrast between the gas and the cylinde r background. 75



### • The Panek 75 

### study did not detect steam that was generated by a pump. H owever, when steam was produced using a hot vapor generator, the plume w as easily visible. 75



### • MDLRs are presented for 20 compounds at three different wind speeds in Tables 3-3 through 3-5. These tables illustrate that higher wind speeds and measuring mixtures of the pollutants versus pure chemical both resulted in higher MDLRs. 522



### Figure 3-4. MDLRs Versus Standoff Distance for Thre e Lenses 5



### Table 3-3. Summary of Controlled Laboratory Testing Minimum Detection Limits (g/hr) at Various Wind Speeds 74

OGI Camera Sherlock GasFindIR

Compound 0 mph 2 mph 5 mph 0 mph 2 mph 5 mph

Benzene 34.72 >66 * ND >70.1 * >70.1 * >70.1 *
Ethylbenzene 20.6 48.9 ND 7.6 5 3.2 >75.9 *
Heptane 13.55 28.8 >51.4 * 3 21 48

Hexane 4.4 18.25 52.1 2.9 37.6 57.8

Isoprene 28.8 >51.4 * ND 32.8 59.6 >59.6 *

Methanol 23.5 55.4 >153.9 * 16.7 41.7 69.3

MEK 32.15 61.1 ND 5.3 60 >70.5 *

MIBK 11.1 60.4 ND 7.01 24.6 70.1

Octane 11.1 31.7 ND 4.36 18.7 62.2

Pentane Not tested Not tested Not tested 13.8 25.4 45.8

1

- Pentene 9.85 >25.2 * ND 14 30.9 47.7

Toluene 34.3 >65.2 * ND 22.6 >75.3 * >75.3 *
Xylene 30.75 64.9 ND 15.1 52.8 >75.3 * * The values in this table with a greater than sign indicate where the gas was imaged at a leak rate a bove that which the laboratory design was to quantify. This represe nts that the gas is able to be detected, but the MD LR could not be determined using the available equipment. ND = N ot Detected.23



### Table 3-4. Summary of Controlled Laboratory Minimum Detection Limits (g/hr) for Pure Gases at Various Wind Speeds 74

OGI Camera Sherlock GasFindIR

Compound 0 mph 2 mph 5 mph 0 mph 2 mph 5 mph

Butane Not tested 2.85 24.25 0.72 5.8 15.9

Ethane Not tested 22.5 41.2 0.97 5.2 1 7.8

Methane Not tested 32 80 3.96 20.8 49
Propane Not tested 7.14 29.1 0.76 9.8 19.1
Ethylene Not tested Not tested Not tested 13.9 53.7 104
Propylene Not tested Not tested Not tested 4.37 15.6 59.8



### Table 3-5. Summary of Controlled Laboratory Minimum Detection Limits (g/hr) for Gases

Diluted with N 2 

### at Various Wind Speeds 74

OGI Camera Sherlock GasFindIR

Compound 0 mph 2 mph 5 mph 0 mph 2 mph 5 mph

Butane Not tested 12.8 24.25 7.9 15.9 21.6

Ethane Not tested 37.5 63.7 5.94 14.5 20.4

Methane Not t ested 68 159 19.8 45.6 65.4
Propane Not tested 27.5 53.9 7.08 16.3 21.8
Ethylene Not tested Not tested Not tested 90.1 >90.1 * >90.1 *
Propylene Not tested Not tested Not tested 24.7 47 62.4 * The values in this table with a greater than sign indicate where the gas was imaged at a leak rate above that wh ich the laboratory design was to quantify. This represents that the gas is able to be detected, but the MDLR could not be determined using the available equipment.



### FLIR developed a second generation GasFindIR and submitted thi s OGI technology update for testing later that same year on the same experimental apparatus at the Naperville, IL facility. The second generation FLIR GasFindIR camera achieved lower MDL Rs for all gases tested and even challenged the lower release rate capabilities of the experimental apparatus. A summary of the MDLR values for the second generation FLIR GasFindIR is presented in Tables 3-6 and 3-7 for all gases and conditions tested. The values in Tables 3- 6 and 3-7 for 0 mph wind speed conditions and pure gas are currently used by FLIR to descri be the gas detection limits of their next generation GasFindIR OGI camera, the FLIR GF320. 33



### In a report prepared for FLIR on both GasFindIR studies, Pane k 75 

### confirmed the conclusions resulting from the study conducted earlier that year, and reiterated that:

• The focal length of the lens did impact the detection c apability of the camera;

• The temperature of the gas relative to that of the backgr ound (the ∆ T) can potentially have large impacts on the MDLR for this OGI technology ; and,

• The uniformity of the background does influence the MDLR fo r this OGI technology.24



### The report by Panek 75 

### reintroduced the importance of temperature differe nces and thermal tuning when operating OGI technology. 75



### Tables 3-6 and 3-7. MDLRs for Pure Compounds at Dif ferent Wind Speeds and Gas Mixtures at Different Wind Speeds 5,75

* It is assumed that the cement board background wa s used (instead of the metal cylinder background) f or this part of the study because the authors did not specify th e exact background used.

* A hot nitrogen gas stream was flowed through a cu stom organic vapor generator system in order to gen erate the gases for the compounds listed in the table on the left, which are normally liquid at room temperature . To make direct comparisons between these MDLRs and those of the compounds from the table on the right (species that are gases at room temperature), the pure gases from the table on the right were diluted with nitrogen at a flow rate similar to that used for the vapor generator (about 3 L/min).



### 3. ETV Minimum Detection Limit Study

The EPA Environmental Technology Verification progr am conducted OGI technology verification studies on the second generation FLIR GasFindIR and the GIT (formerly PAT)

Sherlock ® 

### VOC cameras in both laboratory (Naperville, IL fac ility) and field conditions in 2008. For the ETV MDL study, gaseous compounds were relea sed from a 1 inch outlet valve under carefully controlled laboratory conditions for each of the compounds listed in Table 3-8 using the same Naperville, IL experimental apparatus discusse d above. Three observers were used to confirm OGI camera detection. Starting at release r ates in g/hr resulting from the Panek 74,75 

### and

Benson 5 

### studies previously discussed as the limit of detec tion for each compound, the mass rate25



### was incrementally decreased if all three observers ide ntified the leak. Once a leak rate that was not identifiable by all three observers was reached, the release rate was then increased until all three observers could again identify the leak with the OGI camera. This procedure was repeated under different test conditions, such as: stand-off dis tance, wind speed, and background material as performed initially during the TCEQ study. The minimum and maximum MDLs presented in Table 3-8 represent the range of MDLs measured over all te st conditions. 10,11



### The ETV study also compared relative OGI camera agreemen t with an approved Method 21 monitoring device during laboratory testing. Once a detectio n level using the OGI camera was found for each test condition, gas concentrations wer e measured according to Method 21 using a PID and a leak definition concentration of 500 ppmv. For situations where the OGI camera MDL was above the highest reliable flow rate of the chemic al delivery system, the OGI camera was noted as not being able to detect the compound under the speci fic test conditions. Similarly, if the Method 21 monitoring device produced a response equal to zero , then the monitoring device was considered unable to detect the chemical gas leak under t he specific test conditions. 10,11



### If both the OGI camera and the Method 21 monitoring device pr oved capable of detecting the gas leak, then both units were considered to have agreed under the specific test conditions. Likewise, if either unit proved incapable of detecting th e gas leak under the specified test conditions, then the units were considered to have disagre ed. The relative agreement between OGI camera leak detection and a Method 21 acceptable monito ring device is listed by camera for each chemical compound tested in Table 3-8. Percent agreeme nt was calculated where A was the number of tests that both units agree and T was the total number of tests in: 	 = 	   !	 × 10026



### Table 3-8. Summary of MDLs and % Agreement with a M21 Monitor ing Device during Lab Testing 10,11

FLIR GasFindIR TM MW Camera

Compound Method Detection Limit (g/hr) Agreement with Method 21 Device

Minimum Maximum Total No. of Tests

Performed Percent Agreement

1,3

- butadiene 1.3 2.7 4 100%

Acetic acid ≤ 0.02 ≤ 4.6 (b), (c) 11 100%

Acrylic acid 0.92 1.2 4 100%

Benzene 0.35 35 (c) 12 100%

Methylene chloride 4.9 > 70 (c) No data (d)

Ethylene 0.35 278 (c ) 8 100%

Methanol 0.28 22 (c) No data (d)

Pentane ≤ 0.28 28 (c) 16 100%

Propane ≤ 0.44 13 (c) No data (d)

Styrene 0.35 0.70 3 100%

Sherlock® VOC

Compound Method Detection Limit (g/hr) Agreement with Method 21 Device

Minimum Maximum Total No. of Tes ts
Performed Percent Agreement

1,3

- butadiene 8.0 27 4 100%

Acetic acid 1.7 81 11 100%

Acrylic acid 0.92 7.4 4 100%

Benzene 3.2 ≥ 70 (b), (c) 10 40%

Methylene chloride ≥ 70 (b) ≥ 70 (b) No data (d)

Ethylene 3.3 ≥ 278 (b) 6 33%

Methanol 2.1 ≥ 69 (c) N o data (d)

Pentane 0.83 ≥ 55 (b), (c) 12 75%

Propane 0.88 235 (b) No data (d)

Styrene 15 25 4 100%
(a) Minimum and maximum method detection limits were me asured at a 0-mph wind speed unless otherwise noted. (b) Measured at a 2.5-mph wind speed. (c) Measured at a 5-mph wind speed. (d) Percent agreement was not evaluated for methylene chloride, methanol, and propane because these compounds have an ionization potential greater than the energy that could be supplied by the Industrial Scientific IBRID

MX6 with PID sensor.27



### The ETV assessment tests did find these same operational results for both cameras:

• Increased stand-off distance led to increased MDLs

• Increased wind speed led to increased MDLs

• The units were both easy to set up and ready to deploy in 10 minutes.

However, the GasFindIR TM 

### MW was significantly lighter in weight (4.6 pounds (lb s)) versus the

Sherlock ® 

### VOC (19 lbs), and optional lenses that are interchang eable with the GasFindIR TM 

### MW offset the increase in MDL with distance from targe t. The Sherlock ® 

### VOC does not have this capability.

4. Attempts at Calibration and Performance Verification

Challenges to acceptance of OGI technology as a standal one technique for LDAR surveys include a lack of detailed information on standardized procedur es to be followed, requirements for formal training of OGI technology operators, and cond itions under which LDAR surveys with OGI technology should be performed. 68 

### Calibration verification is a quality assurance procedure typically implemented through prescriptive methods and/or standard operating procedures that objectively measures the performance of O GI technology prior to field deployment to ensure data of known quality. Calibration e quipment and techniques are currently being discussed and refined, but in general include: the detect ion of a reference cell as compared to a cell filled with gas (see Figures 3-5 and 3-6) or an added c alibration component to be

attached to the OGI camera.

In the first calibration option, shown in Figure 3-5, a chambered vessel is filled with different gases of known concentrations and mounted onto the lens of the OGI camera. A video overlay allows the user to adjust camera settings to align the ga in and level amounts to match with the desired gas at the desired concentration allowing the came ra to be calibrated. 628



### Figure 3-5. Calibration Chambered Vessel 6



### Alternatively, the raw pixel intensity from the OGI camera’s detector can be used in a laboratory set up (shown in Figure 3-6) developed with a gas cell and a r eference cell against a temperature controlled background. In this pixel intensity approach, the OGI camera images are processed with a pixel intensity analyzer (PIA)—or software algorithm that gathers and evaluates the raw pixel data from the detector—and are used to construct a qual ity control chart that defines the quality control criteria. 131 

### The following paragraphs discuss this calibration verific ation concept further; the use of a PIA to develop a quantitative OGI me thod will be discussed later in this

document.

Using the set up illustrated in Figure 3-6, researchers 131 

### were able to develop theoretical relationships between the difference in pixel intensity measurements between the gas cell and the reference cell ( Δ I) and the difference between the gas cell temperature and the background board temperature. Using a gas cell filled with a known gas at a known concentration and varying the temperature of the background board, a calibration verificat ion quality control chart, such as the one calculated in Figure 3-7, can be developed as part of a daily OGI calibration check routine, complete with bound compliance criteria windows. 13129



### Figure 3-6. Gas Imaging IR Camera Verification and Calibration System 131



### Figure 3-7. Quality Control Chart for IR Camera Dai ly Check 131



### Repeating this experiment with many different gases at many different concentrations yields a library of response clusters, such as the one in Fi gure 3-8. Therefore, being able to know the temperature difference ( Δ T) between the target gas and the background—and if imaging a pure component or a specific mixture of components for w hich a cluster has been developed—allows the operator to determine the concentration-path le ngth. For example, if the Δ T was 9°C (as30



### shown in Figure 3-8 with a dotted blue vertical lin e), then the camera operator should be able to determine the concentration-path length using a plo t of the Δ I of the target plume and the background as demonstrated in Figure 3-9. 131



### Figure 3-8. Example of a Cluster of **Δ** I vs. **Δ** T Curves for Different PPM-M Levels of

Benzene 131



### Figure 3-9. Example of a **Δ** I vs. Concentration-Path Length Curve 13131



### A Benson et al. study 7 

### from 2008, which looked for camera signal intensity with gas reference cells (set up is shown in Figure 3-10), used the change in si gnal intensity (Figure 3-11) to develop OGI camera sensitivity functions. Plotting th e amount of signal attenuation versus concentration in Figure 3-12 showed a way to predict OGI ca mera minimum detectible leak rates, and also illustrated the effect of maximum optic al attenuation, the phenomenon by which an increase in gas concentration will no longer result in a larger signal because the optical signal

has reached maximum attenuation. This is illustrated in F igure 3-12 as the point where the signal-to-noise ratio (S/N Ratio) begins to level off

.

Figure 3-10. Experimental Set Up of Gas Cells with Controll ed Blackbody Sources 7



### Figure 3-11. Measurement of the Signal Attenuation from 2,000 ppm of Methane 732



### Figure 3-12. Signal Attenuation vs. Gas Concentration 7



### Recently, Sandsten et al. took this concept a step furthe r and defined the noise equivalent concentration length (NECL) derived from OGI camera gas absorption curves as a promising metric for establishing OGI camera performance. 88 

### Similar to the way in which the noise equivalent temperature difference (NETD) is used to charac terize the performance of thermometric instruments by defining the smallest amount of temperature difference that can be definitively measured above noise levels (like the limi t of detection in analytical chemistry), the NECL describes the performance limitations for OGI cam eras in terms of the lowest ppm•m that

can be detected above the baseline noise. As a measure of the sensitivity of an OGI camera to a specific gas, the NECL value depends on ∆ T, the concentration of the target gas, and the depth of the gas plume along the optical axis of the OGI cam era. Their studies, presented in 2015, used a similar design to those mentioned above where a test cell of specified gas concentration (at ambient temperature) is placed between the OGI camera and a blackbody background able to maintain a stable temperature at 30°C (about 10°C above amb ient), as illustrated in Figure 3-13. The gas concentration is varied by pre-filling gas cuvettes with different gas concentrations and placing them inside the holder (small white box in Figure 3-13) located 1.0 m away from the lens

of the OGI camera.33



### Figure 3-13. NECL Measurement Set Up 88



### A proxy measurement of the signal intensity is reco rded from the set up in Figure 3-13 as apparent temperature of the black body background t hrough the test gas and plotted over the path-integrated concentration length (CL, in ppm•m) in Figure 3-14. During these measurements,

the ∆ T was recorded by monitoring the temperature differ ence between the black body radiator and the test gas.

Figure 3-14. Signal Intensity as a Function of CL 88



### By developing a derivation of the Beer-Lambert law to integrate the signal over the OGI cameras spectral range of operation, Sandsten et al. calcul ated a line of best fit (green dashed line in Figure 3-14) through the experimental data obtained during their study (blue circles in Figure 3-34



### 14) and extrapolated the line function to CL = 0 to find th e NECL. The fit-function of the line in Figure 3-14 can be described by the following relationship:



# % & ', ) ∝ 

+ + '

Where the radiative signal ( S ) for a given ∆ T ( T ) and CL received by the OGI camera through a plume of pollutant are proportional to line fit factors A and B and the CL . In this way, Sandsten

et al. determined the NECL of methane for the FLIR GF320 to be 13 ppm•m. Sandsten et al. verified this NECL result by simulating a theoretical v alue through calculations with spectral compound data from the HiTran database. These calculatio ns are displayed in Table 3-9 where the empirical results are shown for different ∆ T amounts with a measure of the instrumental error and the simulated results for comparison in parentheses

. 88



### Table 3-9. Empirical Methane NECL Values for a FLIR GF320 OG I Camera 88

CL ( ppm•m) ∆ T = 2 °C ∆ T = 5 °C ∆ T = 10 °C

0 75 ± 4 (76) 28 ± 1 (28) 13 ± 1 (13)

10 76 ± 4 (77) 29 ± 1 (29) 13 ± 1 (13)

100 87 ± 4 (90) 33 ± 1 (34) 15 ± 1 (15)

1000 235 ± 3 (239) 88 ± 1 (90) 40 ± 1 (40)



### In order to develop a standardized metric that objectivel y describes the performance of an OGI camera, Sandsten et al. proposed measurement condition s (highlighted in green in Table 3-9) that

should remain constant so that the NECL results for mul tiple cameras of different types can be compared. These conditions are:

• ∆ T = 10°C

• The OGI camera to be tested is set up 1.0 m from the gas cell

• After the line of best fit is optimized (through the A a nd B factors), the NECL is evaluated at a CL = 0 ppm•m.

Also, this metric can be applied to describing potential fi eld performance. For example, a NECL of 13 ppm•m for methane with a gas plume that is 10 cm in optical depth translates to the OGI camera being technically capable of detecting the plume if it has a concentration greater than 130 ppm (13 ppm•m / 0.1 m). This limit of detection will increase , however, in a manner

commiserate with field conditions at the time of detec tion (e.g., wind speed, leak exit velocity, background temperature and uniformity, distance from targete d equipment).35



### 5. Studies to Compare OGI Technology to Method 21

Many studies have been conducted to evaluate the ability of O GI technology to perform comprehensive LDAR leak surveys and compare the results b etween OGI technology monitoring and Method 21 monitoring.

Robinson and Luke-Boone 84,85 

### performed a study that tested the capabilities of the ac tive IR imaging BAGI camera at ethylene chemical plants and refine ries. It was shown that the OGI camera was able to consistently detect unsaturated (gas f eedstock has a higher percentage of olefinic—or unsaturated—chemical compounds) gas plant leaks a t 20 g/hr or above as determined by bagging; however, a modified background (somethi ng to reflect the IR output, such as brightly reflecting Styrofoam) was needed to con sistently image leaks at lower rates. The BAGI camera only missed 3 out of a total 27 leaks detected w here all 3 of the missed leaks were measured to have a mass emission rate of 5 g/hr or less. However, it was observed during the surveys that multiple LDAR leak identification tags re sulting from Method 21 surveys were actually misidentifications due to the lack of visual conf irmation. Additionally, operators conducting LDAR surveys using Method 21 only were able to screen between 500 and 700 equipment components per day, whereas the OGI technology -assisted surveys increased that rate to 2,100 equipment components per hour. The study showed that the potential cost savings was outstanding based on the rate at which LDAR operators c ould perform the survey. 84



### The same screening rate inequality was found in a differen t study by Picard et al. 78 

### at a gas fractionation plant, where the implementation of OGI technology increased the screening speed nearly 10-fold. 78 

### For a two person team using Method 21, a rate of 240 components per hour was a reasonable pace. A two person team using OGI increases that rate to 2,300 components per

hour. 81 

### Of the top 10 biggest leakers found during this study, operators only found 5 while using Method 21, but found 8 while using OGI technology (the other 2 leaks having sufficient mass emission rates to be detected by the camera, but were missed by the operator f 

### ). While the study emphasized the detection performance for the top 10 leaks, there was no comparison of performance over the entire size range of leaks. Add itionally, this study found that as compared to Method 21, OGI technology had the following advantages an d disadvantages. 78



### Advantages Disadvantages

Able to visualize difficult and hard-to-reach

leak locations. Is not recommended for use during rain, fog, or in extreme cold. Also may not be as effective during overcast conditions.

Can clearly “see” the source of the leak. Needs a knowl edgeable operator.

Reduces equipment operator exposure to

vapors. Unable to quantify emissions.

f Operator sensitivity to contrast differences varies widely from person to person and depends on multiple factors such as pupil dilation. For more on the capabilities of the human eye, see Optical Modulation Transfer Function s of the Human Eye. 5536



### During a study by Reese et al., 2006, it was determined that onl y two people were required for 2 days to do an OGI technology-assisted facility survey versus four people for 4 days using

Method 21. 80 

### In this study, the authors allowed some leaks that were less than the regulation definition of 10,000 ppm to go unrepaired to evaluate the conce rn over the potential for leaks at lower mass emission rates to become bigger over time. T hese equipment leaks were re-surveyed three months after the initial Method 21 survey. Although some leak rates increased over that time, an equivalent amount of leaks decreased, resulting in no net change over time and resulting in the authors unable to find any correlation between lea k rate and length of time.

Reese et al. reported that, during the last comparison survey conducted for this study, only one leak was detected with OGI technology and nine leaks were detected with Method 21 independently. In this example, although the Method 21 survey found more leaks, the maximum leak concentration detected by Method 21 was 5,817 ppm. In com parison, the one leak found by OGI technology measured 210,000 ppm; this was the largest leak of the study, and it was not detected via Method 21. Therefore, lower whole-facility e missions can result from the implementation of OGI technology-assisted leak surveys due to the greater probability of a large leak being detected with OGI versus Method 21 only. Reese et al. 80 

### reached this conclusion after observing that OGI consistently found the larger leaks, al though some leaks were missed starting around 6,000 ppm (according to EPA Method 21 measurements) and le ss. 80 

### In the study, the authors applied the EPA correlation curves 106 

### to Method 21 screening values and the API

leak/no-leak emission factors 2,3,59,60 

### to come up with whole facility emission rates of 9,099 pounds per year (lbs/yr) for Method 21 and 7,774 lbs/yr for OG I. This was a difference of about 15%, which was acceptable to the authors. 80 

### The study authors concluded that the use of OGI technology to assist LDAR surveys results in lower wh ole-facility emissions versus Method 21 alone and that the amount of emissions released by small er leaks possibly missed by OGI technology-assisted surveys are offset by the faster i dentification (and repair) of larger leaks when surveys are conducted on a more frequent basis.

6. Studies Comparing OGI Technology to “Bagging” Techniques

While the fugitive emissions from individual equipment ma y be small, the large number of leaking equipment that can be found in typical refinery or petrochemical processing plants

results in the total amount of emissions from this sour ce category being about 50% of the total facility hydrocarbon emissions. 35 

### Developed in response to the 1997 API study, 1 

### which showed that a very small fraction of equipment leaks contri bute a large majority of the controllable fugitive emissions, Smart LDAR programs target these la rger leakers. OGI technology has the potential to assist LDAR programs by increasing the effici ency and cost effectiveness of leak detection surveys, but data on the applicability of OGI t echnology still needs to be collected in order to confirm the leak detection capabilities of this de veloping technology. The studies conducted by Furry et al., 2006 35 

### and Thoma, 2009 122 

### compared results between OGI technology and bagging techniques to add to the body of knowledge on OGI t echnology leak detection capabilities.

Furry et al., 2006 tried to validate the laboratory control led minimum detection leak rates (MDLRs) for OGI technology previously developed by Panek e t al. 74 

### and Benson et al. 5 

### by comparing these earlier published values with field data col lected using Method 21 and bagging techniques from targeted chemical plant process unit areas

. 35 

### The study team quantitatively37



### validated the OGI technology leak detections made in the field with a FLIR GasFindIR by obtaining a screening value for the leaks using a Method 21-appro ved PID/FID analyzer and “bagging” some of the leak emissions for laboratory gas c oncentration analysis and emission rate

measurements. The results of this effort are illustrat ed in Table 3-10 where the MDLRs at various wind speeds determined from the Panek and Benson studie s are compared to the results from the field study conducted for this effort. 35 

### The Panek and Benson results are discussed in detail in Section III.B.2 of this document, and it is wo rth noting that the range of MDLR values presented by Furry et al. in Table 3-10 for the Panek et al. study is for the first generation FLIR GasFindIR OGI camera. Therefore, evaluating Table 3-10 wit h respect to the range of MDLR values from the Benson et al. study, which were conducted o n the second generation FLIR GasFindIR OGI camera, may be more useful, although it i s unknown which generation FLIR GasFindIR OGI camera was used for conducting the field tes ts.

Table 3-10. Comparison of Field-Derived Values to Published L aboratory Detection Limits (g/hr) 35

Chemical Field Test Panek et al., 2006 74 Benson et al., 2006 5

Methane 3.7 3.96

– 49 0.8

– 11

Propane 4.7 0.76

– 19.1 0.4

– 9.3

Butane 10.6 0.72

– 15.9 0.4

– 13

Propylene 23.8 4.37

– 59.8 2.9

– 35

Toluene 50.2 22.6

– 75.3 3.8

– 14.3

Xylene 17.8 15.1

– 75.3 1.9

– 18.9



### In Furry’s study, the monitoring team was able to screen at a rate of 3,600 components per hour and were able to confirm the applicability of lab-derive d detection limits as predictive values for field operation. This study also showed that leaks were successfully detected against many different backgrounds representing various reflectivities, as long as there was a sufficient ∆ T. It is worthwhile to note that wind speed, optical resolution , plume motion, and viewing angle are all parameters that will influence detection sensiti vity, and so the comparison between the fieldderived detection limits and the MDLRs determined under ideal laboratory conditions are expected to be different. 35 

### However, evaluating the field-derived MDLRs with respect to both published MDLR ranges in Table 3-10 shows that the laborator y results are able to provide predictive performance ranges for field applications of O GI technology.

In 2008, multiple interested parties collaborated on a st udy investigating fugitive emissions from petrochemical barges using OTM-10, OGI technology, and “baggi ng” techniques. 122 

### The activities included using the LSI Hawk (FLIR GasFindIR) to image barges from a helicopter, from the ground standing on the edge of the lock as vessel s passed through channel locks, and from the ground on the barges themselves. The “bagging” te chnique was used to quantify emission rates visualized from the aerial survey, and O TM-10 with OP-FTIR was used to quantify emission rates from barge vessels as they move d through the channel locks. The following general conclusions were made from this study: 12238



### • Aerial IR images from OGI technology identified barges, and even barge equipment, with big leaks, whereas ground-based and onboard IR images from OGI technology detected leaks at lower emission rates in addition to the larg er leaks.

• OGI IR equipment was found to be robust, easy-to-use, and pos sessing sufficient detection sensitivity for all applications in this study.

• OGI technology detection was easier to perform during mid -day to late afternoon time periods because of more favorable background conditions durin g those hours. The higher sun position during those hours heated the background scenery ( the barges) to effectively

raise the ∆ T while also reducing the interference caused by shadows.

• Onboard OGI technology detection was less sensitive to a mbient conditions as compared

to aerial observations.

• OGI technology measurements were able to detect leaks fr om barges in the lock that ranged from 169 to 12,204 g/hr alkane mixture as measured by OTM-10.

• Aerial images were identifying leaks that were quantified by bagging as being in the range of 252 to 20,772 g/hr for individual components, relating to total barge leak rates of 4,068 to 22,464 g/hr.

• In all, there were seven instances where leaks were detected from passing barges in the lock by OGI technology, but the plumes never crossed the o ptical path of the OTM-10, thereby missing the leak quantification via OTM-10.

C. Conclusion

Two commercially-viable cameras are on the market today and available for leak detection work: the FLIR GF320 and the Opgal EyeCGas provided by Guardian Comp liance. These two units are extremely similar and operate based on the same passive IR OGI technology imaging principles. There are several key differences in the design and f unctionality of the camera systems (as shown in Table 3-11), including the type of FPA detector use d and the ability to measure temperature as well as image the gas. In addition to the differences noted below, the EyeCGas is intrinsically safe whereas the GF320 is not.

Table 3-11. Comparison Between FLIR GF320 and Opgal EyeCGas Specif ications 33,73



### Specification FLIR GF320 Opgal EyeCGas

Field-of-View/minimum

focus distance 24° x 18° / 0.3 m (1.0 ft) 18.2° x 13.6° / 0.5 m (1.6 ft)

Lens F-number 1.5 1.1

Thermal Sensitivity/NETD <15 millikelvin @ 30°C <12 millikelvin @ 25°C39



### Table 3-11. Comparison Between FLIR GF320 and Opgal EyeCGas Specif ications 33,73



### Specification FLIR GF320 Opgal EyeCGas

Focus Modes Auto or manual Manual

Zoom 1-8x continuous, digital 2x, 4x, digital

Focal Plane Array InSb (3.2 – 3.4 μm) HgCdTe (3 – 4 μm)

Spectral Filter 3.2 – 3.4 μm cold bandpass 3.2 – 3.4 μm hot bandpass

IR Resolution 320 x 240 pixels 320 x 240 pixels

Sensor Cooling Stirling

Microcooler FLIR MC-3 Ricor K563

Full Frame Rate 60 Hz 30 Hz

Display Built-in, 4.3” LCD, 800 x 480 pixels Built-in, 3.5” LCD, 640 x 480 pixels

Viewfinder Built-in, 800 x 480 pixels None

Automatic image adjustment Continuous/manual; linear or histogram based Automatic. Manual for Enhanced Mode adjustment

Manual image adjustment Level/span Enhanced Mode (depth/background)

Image modes IR-image, visual image, High Sensitivity Mode (HSM) IR-image, visual image, Enhanced Mode (Enh)

Temperature measurement

range -40 to +350°C None (does not perform temperature measurements)

Temperature measurement

accuracy ± 1°C for temp range 0 to 100°C, or ±2% of reading for temp range >+100°C None (does not perform temperature measurements)

Meta data recording GPS Audio via Head Set

Video output Removable SD (plus other connections)

Visual image can be

associated with video recording SD not removable (USB connection)

Visual image can be recorded in the same footage with the IR video image

Battery operating time > 3 hrs @ 25 °C, typical use > 4 hrs @ 25°C, typical use

Start-up time < 5 min @ 25°C < 8 min @ 25°C

Operating temperature

range -20 to +50°C -20 to +50°C40



### Table 3-11. Comparison Between FLIR GF320 and Opgal EyeCGas Specif ications 33,73



### Specification FLIR GF320 Opgal EyeCGas

Weight incl. lens and battery 2.48 kg (5.47 lbs) 2.68 kg (5.9 lbs)

Size incl. lens (LxWxH) 12.0 x 6.7 x 6.3 in. 9 x 5.1 x 4.3 in.

Accessory lenses (mid-wave band) 24°, f = 23 mm 14.5°, f = 38 mm 6°, f = 92 mm 18.2°, f = 30 mm 7.3°, f = 75mm

Table 3-12 presents the MDLRs claimed by the manufacturer f or the FLIR GF320 as reported by Panek for the FLIR GF320 predecessor, the second generation FLIR GasFindIR. 75 

### There have not been any MDLR studies performed on the EyeCGas to da te. Given the lack of studies involving the EyeCGas and, as a result, the lack of infor mation available on its performance, it seems worthwhile to include the EyeCGas camera in future studies for model performance intercomparisons, such as the laboratory studies described in S ection IV of this document.

Table 3-12. Minimum Detected Leak Rates (MDLRs) for the F LIR GF320 per

manufacturer

33



### Gas MDLR

(g/hr) Gas MDLR (g/hr) Gas MDLR (g/hr)

1-Pentene 5.6 Heptane 1.8 Octane 1.2

Benzene 3.5 Hexane 1.7 Pentane 3.0

Butane 0.4 Isoprene 8.1 Propane 0.4

Ethane 0.6 MEK 3.5 Propylene 2.9

Ethanol 0.7 Methane 0.8 Toluene 3.8

Ethylbenzene 1.5 Methanol 3.8 Xylene 1.9

Ethylene 4.4 MIBK 2.1

* MDLR values for zero wind conditions from report by P anek, 2005. 7541



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### IV. ERG LABORATORY EVALUATIONS

This section summarizes the experimental laboratory st udies conducted by ERG under EPA contracts EP-D-11-006 and EP-W-09-033 to evaluate the performa nce and application of OGI technology for leak detection. OGI has the potential t o accurately identify leaking equipment and streamline the surveying process for LDAR programs. However , in order to fully understand the capabilities of OGI so that it can be implemented as a standalone monitoring technique, substantial technology performance testing needs to be co nducted to better quantify and qualify the applicability, issues, and operation of OGI cameras for LDAR activities. In the work conducted for the EPA to date, ERG evaluated the followin g parameters (with more studies currently ongoing):

• Technology Feasibility Study – Initial demonstration of laboratory equipment and procedure used to determine the detection capabilities of an OGI camera at different gas concentrations and flow rates under controlled settings.

• Spectral Limitation Study – Documented the spectral operat ing window for multiple OGI cameras to define a predictable window-of-operation with k nown variability between

same and different OGI camera makes and models.

• Gas Sensitivity Threshold Study – Evaluated the response of multiple OGI cameras to various test gases at different concentrations to devel op a response curve with gas threshold detection levels. To be used for calculating OG I camera response factors relative to propane.

• Repeat Feasibility Study – Observed side-by-side comparisons of OGI camera operation and leak display with cameras from two different manufa cturers.

• Horizontal Wind Shear Study – Observed the impact of vario us wind speeds perpendicular to the leak axis on OGI leak detection when all other parameters are

controlled.

• Reynolds Number Study – Observed the impact of leak source e xit face velocity (or gas leak exit pressure) by changing the size of the exit leak or ifice and varying the mass

emission rate.

• Temperature Differential Study – Investigated the impact of various temperature differentials ( ∆ Ts) between the gas plume and the background scenery on OG I camera leak detection when the background is warmer and colder th an the gas.

• Sky Background Data Collection – Observed the impact of dif ferent sky background conditions on OGI gas leak detection.

NOTE: All concentrations seen throughout this section r epresent the actual concentration of the gas before it is released as a simulated leak. Unles s otherwise noted, the gas used for this study is nominally a 50/50 blend of propane and butane. The conce ntration of the gas should not be directly related to a Method 21 response without c onsideration of method specific50



### conditions (e.g., calibration gas, response factors, an alyzer precision, environmental factors, leak geometry).

Similar to how regular cameras produce images using the visib le light region (about 0.40 to 0.75 μm) of the electromagnetic spectrum, OGI cameras produc e thermal images (called thermograms) from the infrared (IR) region (about 1.0 to 14.0 μm) of the electromagnetic spectrum. OGI cameras are a type of thermographic imager w here a special optical component— called a band-pass filter—filters the incoming radiation to a very specific region. In the case of OGI cameras that target hydrocarbons (HCs), the region that is allowed to pass through to the camera’s detector to make the image is from about 3.2 to 3.4 μm, which corresponds to the bandwidth of the energy absorbed by many compounds containing c arbon-hydrogen (C-H) bonds. Therefore, the OGI camera produces a thermogram o f the heat distribution in the field-ofview (FOV) where the presence of a plume of HC gas is represented by a change in heat. Like the way a shadow blocks incident light in the visible ran ge, a plume of HC gas “blocks” the heat signature from the background thermal profile from being ima ged in the IR, whether that background is hotter or colder than the gas plume. When t he apparent background is hotter than the gas plume, the C-H bonds will absorb the heat signa ture and block the background thermal profile with a “cold” shadow. When the apparent background is colder, the C-H bonds will emit a hotter heat signature and block the background thermal pro file with a “hot” shadow. Because OGI camera technology is based on thermal properties, some OGI cameras are developed with the ability to measure the apparent temperature of objects in the FOV; this capability is referred

to as “thermometric” in this document.

The Stephan-Boltzmann Law explains the relationship where a change in the temperature of an object is proportional to the radiation output of that object; for example, an increase in the object’s temperature results in an increase in the amou nt of IR radiation being emitted by that object. The total amount of radiation detected by the ca mera from an object is equal to the sum total of the amount of radiation emitted by the object, t he amount of radiation transmitted by the object (unless the object is opaque) and the amount of radiat ion reflected by the object. Some OGI camera developers have created temperature calibration curves in the camera’s firmware where, if the user inputs an accurate emissivity value ( or ratio that describes the object’s ability to emit radiation relative to a perfect blackbody emit ter) and is able to view the object without transmissive or reflective interference, the intensity of the radiation received by the camera’s detector is an accurate measure of the object’s “apparen t temperature.” In the presence of an HC gas plume, an object’s perceived radiation intensity will be partially occluded by HC gas absorption and the resulting apparent temperature of the o bject as measured by an OGI camera will change proportionally with the amount of gas betwee n the object and the camera. Therefore, many of the studies presented in this section utilize mea surements of apparent temperatures from FLIR GF320 cameras to objectively evaluate camera perform ance.

A. Feasibility and Detection Limit Study

ERG designed a custom controlled leak generation system (CL GS) to allow the observation of OGI technology leak detection performance under carefull y controlled laboratory settings. The objective for the CLGS was to allow precise blending of pollutant gas with diluent gas so that a leak of known concentration, flow rate, and mass emis sion rate is released out a 2” opening in front of a background with a known temperature that is sta ble, controllable, and different from51



### the gas temperature. The blending system design is illustr ated as a schematic in Figure 4-1 and the whole CLGS system is shown in Figure 4-2. Figure 4-2 a lso shows the equipment used to monitor the temperature of the gas, the temperature of the background plate, the temperature of the hood space, the relative humidity of the hood spac e, and the wind speed generated from the hood system ventilation (the last 3 conditions monito red by the “Met Sensors” labeled in Figure 4-2). The experimental gas plume is delivered from a 2” PVC pipe in front of a temperature controlled custom-built cold plate painted with Krylon #51602 U ltra Flat Black spray paint to reduce thermal reflection. See Appendix C.1 of this document for more detail on the CLGS design.

Figure 4-1. CLGS Gas Blending Component Developed by ERG for Preliminary

Performance Tests52



### Figure 4-2. Overview of CLGS in Place at ERG’s Laboratory

The first task conducted was a feasibility study using the CLGS, a 2% total hydrocarbon test gas blend of propane and butane, and a tripod mounted FLIR GF320 OGI camera. This initial study had two objectives: (1) to see if the CLGS design worked a nd was appropriate for FLIR GF320 camera performance testing; and (2) to determine at what concentration level and mass emission rate the FLIR GF320 camera lost detection when imaging le aks of various concentrations and mass rates. The settings on the OGI camera were held constant throughout the testing unless otherwise noted. More detail on the experimental desi gn can be found in Appendix A.1: Test

Plan.

For the purposes of this feasibility study, the leak had to be easily noticeable within 5 seconds of viewing the FLIR GF320 camera output displayed on a 40” flat s creen TV (to assist with the execution of the tests by one analyst and verified by obs erving the FLIR GF320 camera LCD screen when leak detection was marginal). Lacking prior experience with the magnitude of the impact ∆ T has on leak detection, the first attempt to execute th is study did not find much success determining limits of detection at a ∆ T = 15 to 16° C, as all concentrations and mass rates wer e detected. The results shown in Tables 4-1 through 4-5 were c ollected later, with the effective ∆ T lowered to 2 to 3°C. Using manual thermal tuning, the level and span of these tests at the lower

∆ T where held equal to those of the higher ∆ T tests for comparison and to challenge the

observer.

NOTE: OGI camera software typically contains an autom ated display algorithm that defines the thermal tuning (grayscale profile) of an image based on establishing the range of temperatures in the FOV (“span”) and calculating the mi dpoint of the span (“level”). Both the GF320 and Opgal have a setting (“auto mode”) that allows th e cameras to automatically53



### adjust the “span” and “level” so that all objects in t he FOV are viewable. Additionally, the FLIR GF320 camera allows manual tuning, a process where the user can manually adjust the display thermal tuning (the “span” and “level”), thereby en abling us to perform a comparison between images produced by the two different ∆ T conditions of our feasibility study while keeping all other conditions the same. The manual therma l tuning settings are not important when imaging in high sensitivity or enhanced modes due to th e self-subtracting nature of the display algorithm. In other words, to increase OGI camera display sensitivity to a gas plume, camera developers designed an algorithm that subtracts the elements of the current frame from those of the previous frame (or average of a predeter mined number of frames) to isolate (and, therefore, amplify) the difference between the frames due to the movement of the gas plume. In this way, the thermal tuning becomes less impor tant, as the image is being constructed from differences in raw pixel intensity in formation from the detector.

A look into the increase in detection capabilities through the use of high sensitivity or enhanced modes was performed at the lowest concentration level (500 ppmv), and the results are shown in Tables 4-6 and 4-7. This test was repeated (Table 4-7 displays t he results of the second run) to validate the results due to the challenging nature of trying to image a leak at a low concentration. Table 4-8 shows an overview of the total results, includi ng the earlier test runs with ∆ T ≈ 15°C. The green shading in the following tables indicates condit ions where easy/definitive detection

was lost.

Table 4-1. Results from Feasibility Study at About 20,000 ppm V (2%) Total Hydrocarbons (50/50 Propane-Butane Mix)

Run ID Test Date Total HC Conc. (ppmV) Total Flow

Rate (L/min) Mass Release

Rate (g/hr) ∆ T (°C) Detected?

1A 2/7/2013 20220 100 255 2.4 Y

1B 2/7/2013 20220 90 229 2.6 Y

1C 2/7/2013 20220 80 204 2.8 Y

1D 2/7/2013 20220 70 178 2.7 Y

1E 2/7/2013 20220 60 153 2.6 Y

1F 2/7/2013 20220 50 128 2.7 Y

1G 2/7/2013 20220 40 102 2.9 Y

1H 2/7/2013 20220 30 77 2.7 Y

1I 2/7/2013 20220 20 51 2.8 Y

1J 2/7/2013 20220 10 26 2.8 Y

1K 2/7/2013 20220 5 13 2.7 N

1L 2/7/2013 20220 10 26 2.7 Y

1K 2/7/2013 20220 5 13 3.0 N
* Reversing the camera’s polarity and adjusting the ther mal tuning allowed the 13 g/hr leak (1K) to be detected aft er this test run.54



### Table 4-2. Results from Feasibility Study at About 10,000 ppm V (1%) Total Hydrocarbons (50/50 Propane-Butane Mix)

Run ID Test Date Total HC Conc. (ppmV) Total Flow

Rate (L/min) Mass Release

Rate (g/hr) ∆ T (°C) Detected?

2A 2/7/2013 10110 100 128 3.1 Y

2B 2/7/2013 10110 90 115 3.1 Y

2C 2/7/2013 10110 80 102 3.1 Y

2D 2/7/2013 10110 70 89 3.2 Y

2E 2/7/2013 10110 60 77 3.0 Y

2F 2/ 7/2013 10110 50 64 3.1 Y

2G 2/7/2013 10110 40 51 3.1 Y

2H 2/7/2013 10110 30 38 3.0 Y

2I 2/7/2013 10110 20 26 2.9 Y

2J 2/7/2013 10110 10 13 3.2 Y

2K 2/7/2013 10110 5 6 2.8 N

2L 2/7/2013 10110 10 13 2.9 Y



### Table 4-3. Results from Feasibility Study at About 5,000 ppm V (0.5%) Total Hydrocarbons (50/50 Propane-Butane Mix)

Run ID Test Date Total HC Conc. (ppmV) Total Flow

Rate (L/min) Mass Release

Rate (g/hr) ∆ T (°C) Detected?

3A 2/8/2013 5055 100 64 2.6 Y

3B 2/8/2013 5055 90 57 2.7 Y

3C 2/8/2013 5055 80 51 2.6 Y

3D 2/8/2013 5055 70 45 2.7 Y

3E 2/8/2013 5055 60 38 2.6 Y

3F 2/8/2013 5055 50 32 2.5 Y

3G 2/8/2013 5055 40 26 2.7 Y

3H 2/8/2013 5055 30 19 2.5 Y

3I 2/8/2013 5055 20 13 2.3 N

3O 2/8/2013 5055 25 16 2.6 Y

3P 2/8/2013 5055 30 19 2.5 Y



### Table 4-4. Results from Feasibility Study at About 500 ppmV Total Hydrocarbons

Run ID Test Date Total HC Conc. (ppmV) Total Flow

Rate (L/min) Mass Release

Rate (g/hr) ∆ T (°C) Detected?

4A 2/8/2013 506 100 6 2.9 N

* Detection at this concentration level and flow rate was not achieved; therefore, further tests were not a ttempted according to original work plan.55



### Table 4-5. Results from Feasibility Study Holding Mass Emis sion Rate Equal to 10 g/hr with OGI Camera Thermal Tuning on Auto (50/50 Propane-Butane Mix)

Run ID Test Date Total HC Conc. (ppmV) Total Flow

Rate (L/min) Mass Release

Rate (g/hr) ∆ T (°C) Detected?

5A 2/21/2013 809 100 10 2.0 N

5B 2/21/2013 1011 80 1 0 2.1 Y

5C 2/21/2013 1348 60 10 2.2 Y

5D 2/21/2013 2022 40 10 2.3 Y

5E 2/21/2013 2696 30 10 2.3 Y

5F 2/21/2013 4044 20 10 2.0 Y



### Table 4-6. Results from Feasibility Study at About 500 ppmV Total Hydrocarbons on High Sensitivity Mode (50/50 Propane-Butane Mix)

Run ID Test Date Total HC Conc. (ppmV) Total Flow

Rate (L/min) Mass Release

Rate (g/hr) ∆ T (°C) Detected?

10A 2/21/2013 506 100 6.4 2.4 Y

10B 2/21/2013 494 90 5.6 2.5 Y

10C 2/21/2013 506 80 5.1 2.5 Y

10D 2/21/2013 491 70 4.3 2.4 Y

10E 2/21/2013 506 60 3.8 2.4 Y

10F 2/21/2013 485 50 3.1 2.7 N

10G 2/21/2013 506 40 2.6 2.4 N

10H 2/21/201 3 539 30 2.0 2.3 N

10I 2/21/2013 506 20 1.3 2.6 N

10T 2/21/2013 485 50 3.1 2.2 N

10U 2/21/2013 478 55 3.3 2.4 N

10V 2/21/2013 515 55 3.6 2.5 Y

* Video files were not recovered from this test run. Test run was repeated due to video recording error. Results fo r rerun are shown in Table 4-7.56



### Table 4-7. Results from Feasibility Study at About 500 ppmV Total Hydrocarbons on High Sensitivity Mode, Rerun (50/50 Propane-Butane Mix)

Run ID Test Date Total HC Conc. (ppmV) Total Flow

Rate (L/min) Mass Release

Rate (g/hr) ∆ T (°C) Detected?

10A 3/12/2013 506 100 6.4 1.9 Y

10B 3/12/2013 494 90 5.6 2.1 Y

10C 3/12/2013 506 80 5.1 2.2 Y

10D 3/12/2013 491 70 4.3 2.1 Y

10E 3/12/2013 506 60 3.8 2.1 Y

10F 3/12/2013 485 50 3.1 2.1 Y

10G 3/12/2013 506 40 2.6 2.0 N

1 0H 3/12/2013 539 30 2.0 1.9 N

10I 3/12/2013 506 20 1.3 2.0 N

10T 3/12/2013 485 50 3.1 2.1 Y

10U 3/12/2013 478 55 3.3 2.0 Y

10V 3/12/2013 515 55 3.6 2.1 Y



### Table 4-8. Overall Results from the Feasibility Study Showin g Both ∆ T Conditions

Test Conditions Detection

Limit Mass Emission

(g/hr) Concentration

(ppmV) Total Flow

Rate (L/min)



### ∆ T ≈ 15°C

Manual Mode Run 1 None reached

- - -

Run 2 None reached

- - -

Run 3 None reached

- - -

Run 4 4O 1.5 485 25

High Sensitivity Mode Run 10 None reached

- - -



### ∆ T ≈ 2 – 3°C

Manual Mode Run 1 1K 12.8 20220 5

Run 2 2K 6.4 10110 5

Run 3 3I 12.8 5055 20

Run 4 4A 6.4 506 100

Auto Mode Run 5* 5B 10.2 1011 80

High Sensitivity Mode Run 10 10G 2.6 506 40

* Due to the nature of this test run, this is the maxim um total flow rate for detection at the 10.2 g/hr rate of

emission.



### The results shown in Table 4-8 indicate that the FLIR GF320 camera should be able to detect a propane/butane gas mixture mass emission rate of 10.7 g/hr ( average of runs 1 through 3) or greater under controlled laboratory conditions, with les s-than-optimal manual thermal tuning,

and with a ∆ T ≈ 2°C. Using the FLIR GF320 camera’s High Sensitivity Mode , the camera could potentially achieve a limit of detection down to 2.6 g/hr under controlled laboratory conditions. The controlled laboratory conditions that were present during this study but that would generally

not be found in the field were:57



### • Tripod-mounted camera

• Consistently low and calm winds produced by the hood face velocity

• Homogenous and non-reflective thermal background

• Knowledge of the leak source

• No thermal interference from the surrounding infrastruct ure.

Other parameters contribute to a leak being detected by an OGI camera beside just mass emission rate, such as the speed at which the gas is exit ing. A leak with a high flow rate will be

harder to detect due to the more diffuse nature of the turb ulent plume, and, conversely, a very slow leak will be harder to detect because it will appear smaller in volume, will be found closer to the leaking equipment, and will sometimes be intermitt ent depending on the wind conditions. By plotting the flow rate data from the feasibility s tudy by the mass emission rate and highlighting the limits of detection (Figure 4-3), it is obvi ous that leak detection at the extremes of gas flow rate will be more challenging in addition t o leaks with low mass emission rates.

Figure 4-3. Feasibility Study Results by Flow Rate and Mass Em ission Rate for

Measurements in Manual and Auto Modes

0 20 40 60 80 100 120

0 50 100 150 200 250 300Flow Rate (L/min)

Mass Emission Rate (g/hr) Detects

Non-Detects58



### B. Spectral Limitations and Gas Sensitivity Studies

The performance capabilities of an OGI camera are a dire ct result of the spectral properties of the IR optics used to construct the camera. The Office of Research and Development (ORD) of the EPA designed the custom-built spectral test platform show n in Figure 4-4 to specifically evaluate the spectral limitations of OGI cameras. One side of the spectral test platform (the left side in Figure 4-4) had a monochromator capable of emitting an IR sour ce from 0.105 to 4.00 μm at a resolution of 1 Å (or 0.0001 μ m), which was used to measure the spectral intensity curve of nine OGI cameras. The other side of the spectral test platfo rm (the right side in Figure 4-4) had optical test cells with internal temperature and pressur e sensors placed in front of a temperature controlled hot plate background. ERG integrated the precise gas dilution system from the CLGS

described in Section IV-A of this document to deliver tes t gas to the cells on the spectral test platform at known concentrations. This was designed such that the spectral sensitivity of OGI cameras to different test gases at various concentrati ons could be evaluated.

Figure 4-4. EPA ORD Custom-built Spectral Test Platform

ERG conducted spectral evaluations on seven FLIR GF320 cam eras, one Opgal EyeCGas camera, and one older model FLIR GasFindIR camera (predece ssor to the FLIR GF320 camera).

The details for the OGI IR cameras used for these eval uations are presented in Table 4-9. The experimental design for these evaluations was initiall y based on the thermometric function (or ability to provide measurements of apparent temperature) a vailable with the FLIR GF320 camera model. The addition of non-thermometric cameras (Opgal E yeCGas and FLIR GasFindIR) into the study required an augmentation to the study design for t hese cameras. Grayscale intensity from IR images recorded by these OGI cameras is used as a proxy for optical intensity. By adding neutral density filters of known optical densities into the field of view during the gas cell59



### tests, a grayscale calibration curve can be developed an d used to evaluate the grayscale values measured from the optical test cells at different conce ntrations. A curve of the normalized grayscale intensity from the monochromator exit image is currently in process for both nonthermometric OGI cameras. An example of this technique g 

### is provided in Figure 4-5 in the visible and the IR. As the preparation of the data colle cted from non-thermometric cameras is ongoing, the results presented at this time are from only the FLIR GF320 cameras evaluated.

Table 4-9. OGI Cameras Evaluated for Spectral Limitations and Gas Sensitivity

Make Model Serial Number Owner/Location

FLIR GF320 44401313 ERG

FLIR GF320 44400966 EPA OECA

FLIR GF320 44400816 EPA R8

FLIR GF320 44401085 EPA OECA

FLIR GF320 44401204 Southern Ute

FLIR GF320 44401135 EPA R3

Opgal EyeCGas* TCG1005011* Guardian Compliance

FLIR GF320 44400819 EPA NEIC

FLIR GasFindIR* BH0115* EPA R6

* These OGI camera models do not have thermometric capa bilities. Therefore, the data collected from these cameras are still being processed.



### Figure 4-5. Example Placement of Neutral Density Filters f or Non-Thermometric IR Spectral Tests in the Visible (Left) and IR (Right)

Each FLIR GF320 camera was mounted onto the spectral test ing platform facing the monochromator and optimized such that the camera’s coo led internal components contributed

g The data from the two non-thermometric OGI cameras us ing this technique are currently being processed under EPA Contract No. EP-D-11-006 Work Assignment 5-09.60



### minimal thermal interference (examples shown in Fig ures 4-6 and 4-7). After allowing the monochromator to thermally equilibrate, the optical intensity (as apparent temperature in °C) for

each FLIR GF320 camera was measured from 3.00 to 3. 65 μ m in increments of 0.01 μ m twice; once ascending from 3.00 to 3.65 μ m, and then repeated descending from 3.65 to 3.00 μ m for verification purposes. Each spectral curve was norm alized to the maximum apparent temperature measured for that curve before being averaged over the entire collection of spectral curves for all FLIR GF320 cameras tested and plotted with 1 σ standard deviation error bars by wavelength (in

μ m) in Figure 4-8. The error bars in Figure 4-8 high light how the FLIR GF320 cameras all respond nearly identically, demonstrating the consi stency of performance for the same make and model camera (the FLIR GF320), regardless of the or iginal date of manufacture.

Figure 4-6. A FLIR GasFindIR Mounted and Aligned to the Monochromator Exit Slit

Figure 4-7. The Exit Slit of the Monochromator as I maged by the FLIR GF32061



### Figure 4-8. Average Spectral Window Curve for FLIR GF320 Cameras

In order to clearly define the spectral limitations of the OGI camera’s optical system (called the “spectral window”), a feature of the spectral curve , termed the “point of limitation” (or POL) was defined as an increase in the optical intensity greater than 30% of the baseline value (evaluated beyond the fringe of the spectral window ). The two locations on the spectral curve

where this occurs are called the POL1-low and POL1- high. A case can be made that only the peak area of optical transmission (the plateau at t he top of the spectral curve in Figure 4-8) should be considered as the camera’s spectral windo w. Therefore, Category 2 POLs were calculated to be the region within which the optica l intensity measurements stay within 5% of the maximum apparent temperature. Table 4-10 lists the results for all FLIR GF320 cameras tested and shows that POLs for Category 1 range from about 3.1 to 3.6 um and the POLs of Category 2 range from about 3.2 to 3.4 μ m. Figure 4-9 shows a graphical representation of t he spectral

window POL locations for the FLIR GF320 cameras. Th e Category 2 POLs seem to correspond to the operating range of 3.2 to 3.4 um advertised by the camera manufacturer.62



### Table 4-10. FLIR GF320 Spectral Window Results

Camera ID Camera Make

and Model Camera Owner T

max (°C) POL 1 (Å) POL 2 (Å)

Low High Low High

44401313 FLIR GF320 ERG 229 30900 35800 32400 33900

44400816 FLIR GF320 EPA OECA 231 30900 35700 32300 33800

44400966 FLIR GF320 EPA Region 8 236 30800 35600 32400 33900

44401085 FLIR GF320 EPA OECA 232 30900 35700 32400 33800

44401204 FLIR GF320 Southern Ute 228 31000 35700 32400 33800

44401135 FLIR GF320 EPA Region 3 228 30800 35500 32400 33800

44400819 FLIR GF320 EPA NEIC 236 30800 35700 32400 33800

Average 30900 35700 32400 33800



### Figure 4-9. Average FLIR GF320 Spectral Window Curv e Illustrating POL Locations63



### By developing an average OGI camera spectral performance cur ve, ERG was able to calculate response factors for various gases relative to propane ( propane relative response factors). Spectral data from the Pacific Northwest National Lab oratory (PNNL) were obtained and analyzed for each of the compounds listed in Table 4-11. The absorbance spectrum for each compound in the range of 3.00 to 3.70 μm was individually scal ed by the average OGI camera spectral performance curve and then integrated to calcula te the total integrated absorbance value presented in Table 4-11. These values were then divided by the total absorbance integrated value for propane in order to determine theoretical response fac tors relative to propane (propane relative response factors or propane RRFs).

Table 4-11. Integrated Spectral Absorbance and Propane Relative Response Factors

Compound Total Integrated Absorbance Propane Relative Response

Factors

1 ,3

- butadiene 0.009 0.26

1,3,5

- trimethylbenzene 0.034 0.95

Acetic Acid 0.003 0.08

Acetaldehyde 0.004 0.12

Acetone 0.007 0.21

Acetylene 0.000 0.01

Acrylic Acid* 0.002 0.05

Benzene 0.013 0.36

Butane 0.043 1.21

Butene 0.025 0.70

Carbon tetrachloride 0.000 0.00

Dimethylformamide 0.019 0.53

ETBE 0.048 1.35

Ethylbenzene 0.030 0.84

Ethylene 0.006 0.17

Formaldehyde 0.007 0.18

Heptane 0.064 1.80

Hexane 0.057 1.61

Isoprene 0.016 0.45

MEK 0.017 0.47

Methane 0.011 0.30

Methanol 0.016 0.44

Methyl ch loride 0.006 0.15

Methylene chloride 0.001 0.03

MTBE 0.045 1.25

m

- Xylene 0.027 0.76

Octane 0.051 2.00

o

- Xylene 0.024 0.76

Pentane 0.051 1.4364



### Table 4-11. Integrated Spectral Absorbance and Propane Relative Response Factors

Compound Total Integrated Absorbance Propane Relative Response

Factors

Pentene 0.024 0.68

Propane 0.036 1.00

Propene 0.015 0.42

p

- Xylene 0.029 0.80

Styrene 0.015 0.42

Toluene 0.020 0.56

Vinyl chloride 0.001 0.03

Water 0.000 0.00

Propane+Butane 0.039 1.10
* The spectra for Acrylic Acid was available from PNNL at only 50°C, versus 25°C as with all other gas spectra

listed here.



### Changes in the method for calculating the propane RRFs (s uch as range of integration and saturation as a function of optical depth) will alter t he resulting propane RRF values. Therefore, to determine the most accurate method of integration, the theoretical propane RRF values in Table 4-11 need to be empirically validated. ERG is curren tly evaluating gas sensitivity assessments as a way to empirically validate the theo retical propane RRFs that we calculated.

The spectral testing platform shown in Figure 4-4 has two optically transmissive, air-tight, gas cells in front of a temperature controlled hot plate. B y integrating the CLGS gas delivery component to the test cells of the spectral testing plat form, we are able to carefully control the concentration of test gas delivered to the test cells. As discussed earlier in this section, the apparent temperature as measured by the FLIR GF320 camera provide s a proxy for optical intensity received by the camera when the background apparent temperature is held constant. An example gas sensitivity curve is provided in Figure 4-10, wher e each blue asterisk represents the

individual measurement for each of the seven FLIR GF320 tes ted at various concentration levels and the red circle is the average of all camera respon ses with black error bars representing 1 σ standard deviation. The dashed line indicates a polynomial C lassical Least Squares line of best fit through the averaged data. By extrapolating the equatio n for this line of best fit, we can calculate the temperature differential of the OGI came ra response at a pre-determined concentration level for all test gases and develop a ra tio of temperature differential responses for each gas to propane and compare this ratio to our theore tical propane RRFs. This work is currently ongoing.65



### Figure 4-10. Example Gas Sensitivity Curve for 50/50 Propane-Butane Mixture

According to the Beer-Lambert law, which describes the relationship between the intensity of light signal as it passes through a media and the propertie s of that media, the IR signal detected by an OGI camera will be attenuated exponentially with i ncreasing concentration. It is hypothesized that the curve at the top end of the line o f best fit in Figure 4-10 indicates the beginning of that exponential attenuation towards optical saturation. This will be investigated further and any influence this may have on the calculated pr opane RRFs will be evaluated.

-0.5 0.5 1.5 2.5 3.5 4.5 5.5

-2000 3000 8000 13000 18000 23000**Bias-Corrected Temperature Differential (Control – Test, °C)** 



## Concentration (ppmV)



## Propane-Butane Mixture

All Cameras

Average

Poly. ( Average)66



### C. Assessment of Parameters that Influence Plume Charac teristics/Detection

It is common knowledge that parameters beyond the camer a’s technical design will influence leak detection success. When attempting to characterize the performance and application of a technology (especially if used for method development purpo ses), the proper identification and quantification of the impact that various parameters wil l have on data quality is paramount. As directed by the EPA, ERG evaluated the influence from par ameters that potentially impact OGI camera leak detection capability by isolating these parame ters in carefully designed laboratory experiments. Some of the parameters tested to date are :

• Different manufacturers – a visual comparison

• Horizontal wind shear

• Reynolds number or leak face velocity

• Hot vs. cold ∆ T.

The side-by-side visual comparison, horizontal wind shea r, and Reynolds number parameters were investigated as part of Work Assignment 3-08 on EPA con tract # EP-D-11-006.

The results from these studies are presented in Tables 4- 12 through 4-26. For images results from both OGI cameras, see Appendix C.2 of this document. Each OGI camera was set to Auto mode unless otherwise specified. The green shading in the followi ng tables indicates conditions where easy/definitive detection was lost, and the orange shadi ng indicates a discrepancy in results between the two cameras. Due to camera design and equipmen t restraints during these tests, it is reasonable to expect a difference of results between the two cameras when investigating the

limits of detection.

Table 4-12. Repeat Feasibility Study Run 1 (2% concentration) w ith FLIR and Opgal OGI

Cameras

Run ID Conc. (ppmV) Total Flow Rate (L/min) Mass Release

Rate (g/hr) ∆ T (°C) Detected by

FLIR? Detected by

Opgal?

1A 20297 100 255 1.3 Y Y

1B 20297 90 229 1.4 Y Y

1C 20297 80 204 1.8 Y Y

1D 20297 70 178 1.8 Y Y

1E 20297 60 153 1.7 Y Y

1F 20297 50 127 1.9 Y Y

1G 20297 40 102 2.0 Y Y

1H 20297 30 76 1.6 Y Y

1I 20297 2 0 51 1.8 Y Y

1J 20297 10 26 1.7 Y Y

1K 20297 5 13 1.6 Y Y67



### Table 4-13. Repeat Feasibility Study Run 3 (5000 ppmV) with FL IR and Opgal OGI

Cameras

Run ID Conc. (ppmV) Total Flow Rate (L/min) Mass Release

Rate (g/hr) ∆ T (°C) Detected by

FLIR? Detected by

Opgal?

2A 5074 100 64 1.6 Y Y

2B 5074 90 57 1.7 Y Y

2C 5074 80 51 1.8 Y Y

2D 5074 70 45 1.5 Y Y

2E 5074 60 38 1.9 Y Y

2F 5074 50 32 1.9 Y Y

2G 5074 40 26 1.7 Y Y

2H 5074 30 19 1.7 Y Y

2I 5074 20 13 1.7 Y Y

2J 5074 10 6.4 1.7 Y Y

2K 5074 5 3.2 1.6 N N

2L 5074 10 6.4 1.4 Y Y



### Table 4-14. Repeat Feasibility Study Run 4 (500 ppmV) with FL IR and Opgal OGI

Cameras

Run ID Conc. (ppmV) Total Flow Rate (L/min) Mass Release

Rate (g/hr) ∆ T (°C) Detected by

FLIR? Detected by

Opgal?

3A 507 100 6.4 2.1 N N

3B 507 90 5.7 1.8 N N

3C 507 80 5.1 1.6 N N

3D 507 70 4.5 2.0 N N

3E 507 60 3.8 2.1 N N

3F 507 50 3.2 1.8 N N

3G 507 40 2.5 2.1 N N

3H 507 30 1.9 2.0 N N

3I 507 20 1.3 1.8 N N

3J 507 10 0.64 2.0 N N

3K 507 5 0.32 2.0 N N68



### Table 4-15. Repeat Feasibility Study Run 5 (10.2 g/hr held const ant) with FLIR and Opgal

OGI Cameras

Run ID Conc. (ppmV) Total Flow Rate (L/min) Mass Release

Rate (g/hr) ∆ T (°C) Detected by

FLIR? Detected by

Opgal?

4A 812 100 10.2 2.3 N N

4B 1015 80 10.2 2.2 N N

4C 1353 60 10.2 2.0 Y N*

4D 2030 40 10.2 1.8 Y Y

4E 2706 30 10.2 1.6 Y Y

4F 4059 20 10.2 2.2 Y Y

4G 8119 10 10.2 1.9 Y Y
* The viewing set up during these tests for the Opgal was no t identical to that for the FLIR. The display TV was smaller and the video output had to be converted from analo g to digital before being displayed. These discrepancies at the margins of detection are not antici pated to be representative of actual in-field performance

.



### Table 4-16. Rerun of Repeat Feasibility Study Run 5

Run ID Conc. (ppmV) Total Flow Rate (L/min) Mass Release

Rate (g/hr) ∆ T (°C) Detected by

FLIR? Detected by

Opgal?

4A 812 100 10.2 1.5 N N

4B 1015 80 10.2 1.5 N N

4C 1353 60 10.2 1.5 N N

4D 2030 40 1 0.2 1.6 N N

4E 2706 30 10.2 1.5 N N

4F 4059 20 10.2 1.4 Y Y

4G 8119 10 10.2 1.3 Y Y



### Table 4-17. Repeat Feasibility Study Run 10 (500 ppmV on High Se nsitivity/Enhanced Modes) with FLIR and Opgal OGI Cameras

Run ID Conc. (ppmV) Total Flow Rate (L/min) Mass Release

Rate (g/hr) ∆ T (°C) Detected by

FLIR? Detected by

Opgal?

5A 507 100 6.4 1.5 N N

5B 507 90 5.7 1.7 N N

5C 507 80 5.1 1.5 N N

5D 507 70 4.5 1.5 N N

5E 507 60 3.8 1.8 N N

5F 507 50 3.2 1.8 N N

5G 507 40 2.5 1.6 N N

5H 507 30 1.9 1.9 N N69



### Table 4-18. Repeat of Feasibility Study Run 5 with FLIR and O pgal on High Sensitivity/Enhanced Mode

Run ID Conc. (ppmV) Total Flow Rate (L/min) Mass Release

Rate (g/hr) ∆ T (°C) Detected by

FLIR? Detected by

Opgal?

6A 812 100 10.2 1.6 Y N*

6B 1015 80 10.2 2.1 Y Y

6C 1353 60 1 0.2 1.5 Y Y

6D 2030 40 10.2 1.9 Y Y

6E 2706 30 10.2 1.7 Y Y

6F 4059 20 10.2 1.9 Y Y

6G 8119 10 10.2 1.8 Y Y
* The viewing set up during these tests for the Opgal was no t identical to that for the FLIR. The display TV was smaller and the video output had to be converted from analo g to digital before being displayed. These discrepancies at the margins of detection are not antici pated to be representative of actual in-field performance

.



### Table 4-19. Horizontal Wind Shear, Normal/Auto Mode

Run ID Conc. (p pmV)

Total Flow Rate (L/min) Mass Release Rate (g/hr) Horizontal Wind Velocity (m/s) ∆ T (°C) Detected by

FLIR? Detected by

Opgal?

2

- 1 20297, 50, 127 1.0 1.8 Y Y

2

- 2 20297, 50, 127 2.0 1.9 Y Y

2

- 3 20297, 50, 127 5.0 2.1 N N

2

- 4 20297, 50, 127 9.0 2.1 N N

2

- 5 20297, 50, 127 12 2.0 N N



### Table 4-20. Horizontal Wind Shear, High Sensitivity/Enhanced Mode

Run ID Conc. (ppmV)

Total Flow Rate (L/min) Mass Release Rate (g/hr) Horizontal Wind Velocity (m/s) ∆ T (°C) Detected by

FLIR? Detected by

Opgal?

2

- 3 20 297, 50, 127 5.0 2.0 Y Y

2

- 4 20297, 50, 127 9.0 2.1 N N

2

- 5 20297, 50, 127 12.0 2.1 N N70



### Table 4-21. Reynolds Number Study Results with 2” Orifice

Run ID Conc.

(ppmV) Total Flow

Rate (L/min) Mass Release

Rate (g/hr) Reynolds

Number ∆ T

(°C) Detected by

FLIR? Detected by

Opgal?

3

- 1A 20297 10 26 244 1.8 Y Y

3

- 1B 20297 20 51 488 1.8 Y Y

3

- 1C 20297 30 76 732 1.8 Y Y

3

- 1D 20297 40 102 977 1.6 Y Y

3

- 1E 20297 50 127 1221 1.9 Y Y

3

- 1F 20297 60 153 1465 1.8 Y Y

3

- 1G 20297 70 178 1709 1.8 Y Y

3

- 1H 20297 80 204 1953 2.1 Y Y



### Table 4-22. Reynolds Number Study Results with 1” Orifice

Run ID Conc.

(ppmV) Total Flow

Rate (L/min) Mass Release

Rate (g/hr) Reynolds

Number ∆ T

(°C) Detected by

FLIR? Detected by

Opgal?

3

- 2A 20297 10 26 475 1.7 Y Y

3

- 2B 20297 20 51 950 1.9 Y Y

3

- 2C 20297 30 76 1425 2.0 Y Y

3

- 2D 20297 40 102 1900 1.8 Y Y

3

- 2E 20297 50 127 2375 2.0 Y Y

3

- 2F 20297 60 153 2850 1.8 Y Y

3

- 2G 20297 70 178 3325 1.8 Y Y

3

- 2H 20297 80 204 3800 1.9 Y Y



### Table 4-23. Reynolds Number Study Results with 1/2” Orifice

Run ID Conc.

(ppmV) Total Flow

Rate (L/min) Mass Release

Rate (g/hr) Reynolds

Number ∆ T

(°C) Detected by

FLIR? Detected by

Opgal?

3

- 3A 20297 10 26 1009 1.9 Y Y

3

- 3B 20297 20 51 2018 2.2 Y Y

3

- 3C 20297 30 76 3027 2.1 Y Y

3

- 3D 20297 40 102 4035 2.1 Y Y

3

- 3E 20297 50 127 5044 2.1 Y Y

3

- 3F 20297 60 153 6053 2.2 Y Y

3

- 3G 20297 70 178 7062 2.0 Y Y

3

- 3H 20297 80 204 8071 2.3 Y Y71



### Table 4-24. Reynolds Number Study Results with 1/4” Orifice

Run ID Conc.

(ppmV) Total Flow

Rate (L/min) Mass Release

Rate (g/hr) Reynolds

Number ∆ T

(°C) Detected by

FLIR? Detected by

Opgal?

3

- 4A 20297 10 26 1992 1.9 N N

3

- 4B 20297 20 51 3984 1.9 Y Y

3

- 4C 20297 30 76 5976 2.1 Y Y

3

- 4D 20297 40 102 7968 1.8 Y Y

3

- 4E 20297 50 127 9960 2.0 N N

3

- 4F 20297 60 153 11952 1.9 N N

3

- 4G 20297 70 178 13 944 1.9 N N

3

- 4H 20297 80 204 15937 2.0 N N



### Table 4-25. Reynolds Number Study Results with 1/8” Orifice

Run ID Conc.

(ppmV) Total Flow

Rate (L/min) Mass Release

Rate (g/hr) Reynolds

Number ∆ T

(°C) Detected by

FLIR? Detected by

Opgal?

3

- 5A 20297 10 26 3979 2.0 N N

3

- 5B 20297 20 51 7958 2.0 N N

3

- 5C 20297 30 76 11936 1.8 N N

3

- 5D 20297 40 102 15915 1.8 N N

3

- 5E 20297 50 127 19894 1.7 N N

3

- 5F 20297 60 153 23873 1.9 N N

3

- 5G 20297 70 178 27852 1.6 N N

3

- 5H 20297 80 204 31830 1.6 N N



### Table 4-26. Reynolds Number Study Results with 1/8” Orifice an d High/Enhanced Sensitivity Modes

Run ID Conc.

(ppmV) Total Flow

Rate (L/min) Mass Release

Rate (g/hr) Reynolds

Number ∆ T

(°C) Detected by

FLIR? Detected by

Opgal?

3

- 5A 20297 10 26 3979 1.2 Y Y

3

- 5B 20297 20 51 7958 1.1 Y Y

3

- 5C 20297 30 76 11936 1.4 Y N*

3

- 5D 20297 40 102 15915 1.1 N N

3

- 5E 20297 50 127 19894 1.3 N N

3

- 5F 20297 60 153 23873 1.0 N N

3

- 5G 20297 70 17 8 27852 0.9 N N

3

- 5H 20297 80 204 31830 0.7 N N * The viewing set up during these tests for the Opgal was no t identical to that for the FLIR. The TV display was smaller and the video output had to be converted from analo g to digital before being displayed. These discrepancies at the margins of detection are not antici pated to be representative of actual in-field performance

.



### Two observations were made after plotting the Reynolds nu mber data in a scatter plot (as shown in Figure 4-11). First, it appears detection becomes more c hallenging around a Reynolds number of 8000. Also, the lower mass emission rate values appear to be more difficult to visualize. However, due to the limited dimensions of this chart, it is not readily apparent that the mass emission rates from this test also correspond to flow ra tes. And, as observed with the initial72



### feasibility study data, the leaks that are being emitt ed at the lower flow rates (and, therefore, mass rates) will be harder to detect.

Figure 4-11. Overview of Reynolds Number Data

D. Camera Field Operation

Laboratory studies are good for isolating specific paramet ers and making observations under carefully controlled conditions. However, the types of conditions experienced in the laboratory are rarely ever encountered in the field. ERG designed a nd constructed the leak simulation platform (LSP, shown in Figure 4-12) to evaluate the operat ion of OGI cameras for leak detection in the field. Three flow meters allow for up to three leak simulations to be flowing at one time. This allows the evaluation of detecting multi ple leaks in close proximity.

Volunteers of all experience levels ranging from never h aving used an OGI camera before to hundreds of hours of OGI camera use in the field and repre senting the EPA, industrial contractors, and camera vendors participated in a blind lea k survey study using the LSP. Table 4- 27 lists all possible leak simulations with the LSP, and Table 4-28 shows the experimental matrix that was adopted partway through the testing (changes were made due to time and resource constraints). Table 4-29 lists each test participant and their experience level prior to running the blind test, and Table 4-30 represents an overview of the resul ts.73Figure 4-12. Custom-built LSP by ERG from the Front (left)and Side (right) Showing Leak Locations74



### Table 4-27. List of LSP Leaking Elements

Leak Identifier Leak Description

A1 Hatch

– Gasket

A2 Hatch

– Closure

B Flange

– Gasket

C Flange

– Attachment

D Ball Valve

– Thru

- valve leak

E Pop

- off pressure rele ase valve

F Gate Valve

– Thru

- stem leak

G Quick Disconnect

– Leak from deformation

H Quick Disconnect

– Gasket leak

I Pump

– Head gasket



### Table 4-28. Initial Experimental Matrix for Blind Surveys

Run ID Leak 1 Leak 2 Survey

Duration (seconds) Survey

Zone Leak ID Conc. Flow Rate (L/min) Leak ID Conc. Flow Rate (L/min)

1 E 2% 40 D 0.2% * 60 15 Point

2 B 2% 60 G 0.2% * 60 15 Point

3 C 2% 20 F 2% 60 300 Free

4 I 2% 60 B 2% 40 300 Free

5 I 2% 60 A1 2% 60 300 Free

6 C 2% 40

-- -- -- 300 Free

7 H 2% 20 F 2% 20 300 Free

8 E 2% 60 D 0.2% * 60 15 Point

9 A2 0.2% * 60

-- -- -- 15 Point

10 G 2% 60 D 0.2% * 60 300 Free

11 E 2% 60 D 0.2% * 60 300 Free

* It was later determined that the 0.2 % (2000 ppmv) concent ration level was not detectable due to the conditions encountered during testing.75



### Table 4-29. List of OGI Camera Operators and Experience Level

Operator Experience Level Description

A 3. Advanced Laboratory Scientist

– Designed Study * Operator had > 100 hours of camera operation experience in the past

year. None of which was in a field setting.

B 1. Novice Environmental Engineer Operator had < 10 hours of camera operation experience. None of which was in a field setting.

C 4. Expert LDAR Survey and Training Director Operator had > 300 hours of camera operation experience in the past 2

years. Almost all of which was in a field setting.

D 3. Advanced LDAR Survey Technician Operator had ~ 40 hours of camera experience in 2013, with a total of

about 150 camera hours over entire career. Almost all o f which was in a field setting.

E 3. Advanced EPA Compliance Engineer Operator had 90 hours of camera operational experience i n 3 years. Hours were a mix of laboratory and field settings.

F 3. Advanced Camera Vendor Technical Design Engineer/Scientist Operator had > 400 hours of camera operation experience st rictly in controlled/laboratory conditions.

G 2. Intermediate Camera Vendor Salesman Operator had ~ 40 hours of camera operation experience i n 2013,

typically in an office or laboratory setting.

H 1. Novice EPA Policy Scientist † Operator had < 10 hours of camera operation experience. None of which was in a field setting.
* This participant was the designer of the study and was t herefore biased.

† This participant was a part of the EPA review team and therefore saw example footage of the leaking equipment prior to the test day.76



### Table 4-30. Overall Blind Survey Results for Leaks Released at 2% Concentration

Leak ID/Type Operator/Camera

A/1 B/1 C/1 C/2 D/1 D/2 E/1 E/2 F/2 G/2 H/1

A1 Hatch - Gasket Y N N
- Y
- Y
- - - -

B Flange - Gasket Y N N
- Y Y N Y Y Y N

C Flange - Attachment N Y N N Y
- Y
- - - -

E Pop-off Y Y N Y Y Y Y Y Y N Y

F Stem Valve Y Y N Y Y Y Y Y Y Y N

G QD - Deform Y Y
- Y Y Y Y Y Y Y Y

H QD - Gasket Y N
- Y N N N N Y N N

I Pump Y Y Y
- N Y Y N Y Y N

1 = FLIR GF320, 2 = Opgal EyeCGas Green = Leak was detected at least 1 time, Red = Leak was not detected, Gray = Not tested due to time and resource constraints. See Appendix C.3 for more information.



### The efforts from this study resulted in the following o bservations:

• Some leaks were harder to visualize than others.

• Although level of experience generally predicted operator pe rformance, it was not

the rule in all cases.

• There was no real discernible difference between the two camera types, although % detected by camera type (see Appendix C.3 of this document ) indicates that the Opgal camera or users of the Opgal camera may have been m ore successful at identifying leaks.

• The 2,000 ppmv (0.2%) test gas was not detectable under non-idea l conditions.

• Capturing video footage is imperative for reviewing and qualifyi ng leak detection.

• The presence of a heat/steam source during the cold, rainy conditions resulted in

interference in leak identification.77



### V. SUMMARY

Through our evaluations and literature research, we ident ified a number of parameters that impact the detection capability of the OGI cameras. The parameters that have been evaluated by ERG and have an impact on the detection capability are:

• ∆ T – The temperature differential between the gas plume a nd the apparent background

• Gas matrix of the plume or leak (speciation and concen tration)

• Mass rate of the leak

• Camera configuration (both equipment and software paramet ers)

• Operator ability

• Wind speed

• Reynolds number of the leak.

Other parameters that were evaluated but are not deemed to substantially impact the detection capability are intra-model variability and performance degr adation over lifespan of camera.

Other potential parameters that have been identified in the literature research as potentially impacting the detection capabilities of the OGI cameras but that have not been evaluated by ERG to date are the line of sight, ratio of FOV to the plum e size and the standoff distance, and thermal interferences (e.g., steam, glint).

Despite the numerous parameters that may affect the de tection capabilities of the OGI camera, the empirical testing in the lab and under proper field c onditions with the LSP showed the ability of the FLIR GF320 and Opgal EyeCGas to detect leaks of 60 g/hr propane at a level of 10,000 ppmv with a knowledgeable camera operator.

While our testing focused on each parameter in isolation, it is important to remember that all these parameters can work in concert to affect the dete ction capability of the OGI camera. Figure 5-1 shows an example concept of an OGI performance envel ope for a camera operating during normal conditions. Once developed, all the points within the highlighted pentagon would define the conditions necessary for valid operation of the OGI camera in order to detect any fugitive emissions that are present. As the point of operation gets closer to the middle of the envelope, the conditions for use of the camera become more optimal , allowing for easier detection of fugitive emissions using the OGI camera. As the point of operation moves toward the outer boundaries of the highlighted pentagon, the conditions for use of the ca mera become less optimal, presenting more challenges to detection of fugitive emissions using th e OGI camera.78



### Figure 5-1. Concept Diagram of OGI Camera Performance Envelope

If there are parameters beyond the operator’s control ( e.g., wind speed) that cause the point of operation to be outside of the normal performance envel ope, there may be a need to develop alternative envelopes to deal with these parameters. For example, requiring a higher ∆ T or higher concentration can compensate for higher wind speeds to allow for a similar mass rate detection. Examples of these adjusted performance envelopes for high er wind speed and higher ∆ T and for higher wind speed and higher concentration as compared to t he normal performance envelope are shown in Figure 5-2. This concept of maintaining the pe rformance capabilities of the camera by requiring one parameter to move inward in order to compe nsate for another parameter that falls outside the performance envelope would be applicable to any of the parameter that define the performance envelope.79



### Figure 5-2. Concept Diagram of the OGI Camera Performance Envel ope in the Presence of

Non-Ideal Conditions

NOTE: The performance envelopes presented in Figures 5-1 and 5-2 represent only a draft concept OGI performance envelope for a FLIR GF320 or Opgal Ey eCGas. Only after further empirical tests of the parameters have been complete d and robust empirical correlations have been derived can a final envelope be determined. Also, these draft concept performance envelopes may not represent all potential parameters that will impact the detection capability.

With the possibility for a variety of technological adv ances of OGI cameras in the future, the development of these performance envelopes may be specifi c to camera models, camera modes, certain standards, and specific leak profiles such that parameters like the gas composition of the

leak and the overall concentration of the leak affect t he performance envelope while certain parameters such as wind have a consistent impact across all types of cameras.80



### VI. LIST OF APPENDICES AND SUPPLEMENTAL DOCUMENTS

Appendix A: Feasibility Study (WA 2-09)

1. Test Plan

2. Final Report

Appendix B: Spectral Testing (TD-19)

1. Spectral Testing QAPP

2. Final Report

Appendix C: Parameters that Influence Detection (WA 3-08)

1. Parameter Testing QAPP

2. Final Report

3. Blind Study Report

Appendix D: BIC® Lighter Study Report

Appendix E: SOP for FLIR Temperature Calibration Verific ation