Determination of Volatile Organic Compound and Greenhouse Gas Leaks Using Optical Gas Imaging

Determination of Volatile Organic Compound and Greenhouse Gas Leaks Using Optical Gas

Imaging

1.0 Scope and Application

1.1 Analytes.

Analytes

CAS No.

Volatile Organic Compounds (VOCs)

No CAS number assigned.

Methane

74-82-8

Ethane

74-84-0

1.1.1 This protocol is applicable to the detection of VOCs, including hazardous air pollutants (HAPs),
and hydrocarbons, such as methane and ethane.

1.2 Scope. This protocol covers surveys of process equipment using Optical Gas Imaging (OGI)
cameras in sectors where the majority of compounds (>75 percent by volume) in the emissions streams
have a response factor of at least 0.25 when compared to the response factor of propane and can be
imaged by the equipment specified in Section 6.0. The specific component focus for the surveys is
determined by the referencing subpart, and can include, but is not limited to, valves, flanges, connectors,
pumps, compressors, open-ended lines, pressure relief devices, and seal systems.

1.3 Applicability. This protocol is applicable to facilities when specified in a referencing subpart. This
protocol is intended to help determine the presence and location of leaks and is not currently applicable
for use in direct emission rate measurements from sources.

2.0 Summary

2.1 A field portable infrared (IR) camera capable of imaging the target gas species is employed to
survey process equipment and locate fugitive or leaking gas emissions. By restricting the amount of
incoming thermal radiation to a small bandwidth corresponding to a region of interaction for the gas
species of interest, the camera provides an image of an invisible gas to the camera operator. The camera
type and manufacturer are not specified in this protocol, but the camera used must meet the specifications
and performance criteria presented in Section 6. The keys to becoming proficient and maintaining leak
detection proficiency using OGI cameras are proper camera operator training with sufficient field
experience and conducting OGI surveys frequently throughout the year.

3.0 Definitions

Ambient air temperature means the air temperature in the general location of the component being
surveyed.

Camera configuration means different ways of setting up an OGI camera that affect its detection
capability. Examples of camera configurations that can be changed include the operating mode (e.g.,
standard versus high sensitivity or enhanced), the lens, the portability (e.g., handheld versus tripod), and
the viewer (e.g., OGI camera screen versus an external device like a tablet).

Delta temperature (delta-T or AT) means the difference in temperature between the emitted process
gas temperature and the surrounding background temperature. It is an acceptable practice in the field to
assume that the emitted process gas temperature is equal to the ambient air temperature.

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Dwell time means the time required to survey a scene in order to provide adequate probability of leak
detection. The dwell time is the active time the operator is looking for potential leaks and does not begin
until the scene is in focus and steady.

Fugitive emission or leak means any emissions observed using OGI from components regulated by
the referencing subpart.

Imaging is the process of producing a visual representation of emissions that may otherwise be
invisible to the naked eye.

Monitoring survey means imaging equipment with an OGI camera at one site on one day. Changing
the site being surveyed or changing the day of imaging constitutes a new monitoring survey.

Operating envelope means the range of conditions (i.e., wind speed, delta-T, viewing distance) within
which a survey must be conducted to achieve the quality objective.

Optical gas imaging camera means any field portable instrumentation that makes visible emissions
that may otherwise be invisible to the naked eye.

Persistent leak is any leak that is not intermittent in nature.

Referencing subpart means a subpart in 40 CFR part 60, 61, 62, 63, or 65 that requires the monitoring
of regulated equipment for fugitive emissions or leaks, for which this protocol is referenced.

Response factor means the OGI camera's response to a compound of interest relative to a reference
compound at a concentration path-length of 10,000 part per million-meter. Response factors are specific
to the OGI camera model and can be obtained from peer reviewed articles or may be developed according
to procedures specified in Annex 1 of this appendix.

Senior OGI camera operator is a camera operator who has conducted OGI surveys for a minimum of
1400 hours over the entirety of his/her career, including at least 40 hours in the past 12 months, and has
completed or developed the classroom camera operator training as defined in Section 10.2.1. Previous 12
months means the 365-calendar days prior to the day of the activity that requires a senior OGI camera
operator. The hours spent by the senior OGI camera operator performing comparative monitoring, either
as part of initial training, retraining, or auditing other OGI camera operators, can be included when
determining the senior OGI camera operator's experience both over his/her career and the past 12 months.

4.0 Interferences

4.1 Interferences from atmospheric conditions can impact the operator's ability to detect gas leaks. It
is recommended that conditions involving steam, fog, mist, rain, solar glint, high particulate matter
concentrations, and extremely hot backgrounds are avoided for a survey of acceptable quality.

5.0 Safety

5.1 Site Hazards. Prior to applying this protocol in the field, the potential hazards at the survey site
should be considered; advance coordination with the site is critical to understand the conditions and
applicable safety policies. This protocol does not address all of the safety concerns associated with its use.
It is the responsibility of the user of this protocol to establish appropriate health and safety practices and
determine the applicability of regulatory limitations prior to implementing this protocol.

5.2 Hazardous Pollutants. Several of the compounds encountered over the course of implementing
this protocol may be irritating or corrosive to tissues (e.g., heptane) or may be toxic (e.g., benzene, methyl

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alcohol, hydrogen sulfide). Nearly all are fire hazards. Chemical compounds in gaseous emissions should
be determined from process knowledge of the source. Appropriate precautions can be found in reference
documents, such as reference 13.1.

6.0 Equipment and Supplies

6.1 An OGI camera model meeting the following specifications is required. This testing can be
performed by the owner or operator, the camera manufacturer, or a third party. As required by Section
8.1, this testing must be performed initially, prior to using the OGI camera to conduct surveys. The
determination in Section 6.1.1 must also be made any time the OGI camera will be used to survey
components on equipment that was not previously included in monitoring surveys or whenever there are
process changes that are expected to cause the gaseous emissions composition to change. The
determination in Section 6.1.2 is only required initially.

6.1.1 The spectral range of infrared radiation measured by the OGI camera must overlap with a major
absorption peak for the chemical target of interest, meaning the OGI camera must be sensitive with a
response factor of at least 0.25 when compared to the response factor of propane for the majority of
constituents (>75 percent by volume) of the expected gaseous emissions composition.

6.1.2 The OGI camera must be capable of detecting (or producing a detectable image of) methane
emissions of 17 grams per hour (g/hr) and either butane emissions of 5.0 g/hr or propane emissions of 18
g/hr at a viewing distance of 2 meters and a delta-T of 5 °Celsius (C) in an environment of calm wind
conditions around 1 meter per second (m/s) or less, unless the referencing subpart provides detection rates
for a different compound(s) for that subpart.

6.2 The following items are needed for the initial specification confirmation of each OGI camera
model configuration, as required by Sections 6.1.2 and Section 8:

6.2.1 Methane test gas, chemically pure grade (99.5 percent) or higher.

6.2.2 Butane test gas or propane test gas, chemically pure grade (99 percent) or higher.

6.2.3 Release orifice, % inch inner diameter.

6.2.4 Mass flow controller or rotameter, capable of controlling the gas emission rate within NIST
traceable accuracy of 5 percent.

6.2.5 An industrial fan, capable of adjusting the sustained nominal wind speeds at regular intervals,
with the ability to maintain a set speed within 20 percent of the target wind speed.

6.2.6 A meteorological station capable of providing representative data on ambient temperature,
ambient pressure, relative humidity, and wind speed and direction at least once every hour, with
equipment meeting the following minimum specifications:

6.2.6.1 Ambient temperature readings accurate to at least 0.5 °C, with a resolution of 0.1 °C or less,
and a minimum range of -20 to 70 °C.

6.2.6.2 Ambient pressure readings accurate to at least 1.0 millibar (mbar), with a resolution of 0.1
mbar or less, and a minimum range of 700 to 1100 mbar.

6.2.6.3 Wind speed readings accurate to at least 0.2 m/s, with a resolution of 0.1 m/s or less, and a
minimum range of 0.1 to 20 m/s.

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6.2.6.4 Wind direction readings accurate to at least 5 degrees, with a resolution of 1 degree or less.

6.2.6.5 Relative humidity readings accurate to at least 5 percent, with a resolution of 0.5 percent or
less, and a minimum range of 10 to 90 percent noncondensing.

6.2.7 A temperature-controlled background large enough for viewing the emissions plume and
capable of maintaining a uniform temperature. Uniform is defined as all points on the background
deviating no more than 1 °C from the average temperature of the background.

6.2.8 T-type probe thermocouple and readout, accurate to at 1 °C, for measuring the test gas at or near
the point of release.

6.2.9 T-type surface skin thermocouple and readout, accurate to at 1 °C, for measuring the
background immediately behind the test gas.

6.2.10 Device to measure the distance between the OGI camera and the release point (e.g., tape
measure, laser measurement tool), accurate to at least 2 centimeters (cm), with a resolution of at least 1
cm.

7.0 Camera Calibration and Maintenance

7.1 The camera does not require routine calibration for purposes of gas leak detection but may require
calibration if it is used for thermography (such as with AT determination features). Operators should
follow manufacturer recommendations regarding maintenance and calibration, as appropriate.

8.0 Camera Specification Confirmation and Development of the Operating Envelope

8.1 Determine that the OGI camera meets the specifications in Section 6.1 prior to conducting surveys
with the OGI camera. The determination in Section 6.1.1 must also be made any time the OGI camera
will be used to survey components on equipment that was not previously included in monitoring surveys
or whenever there are process changes that are expected to cause the gaseous emissions composition to
change. The determination in Section 6.1.2 is only required initially. The results of this determination
must be documented.

8.2 Field conditions such as the viewing distance to the component to be monitored, wind speed,
ambient air temperature, and the background temperature all have the potential to impact the ability of the
OGI camera operator to detect a leak. It is important that the OGI camera has been tested under the full
range of expected field conditions in which the OGI camera will be used.

8.3 An operating envelope must be established for field use of the OGI camera. Imaging must not be
performed when the conditions are outside of the developed operating envelope.

8.3.1 The operating envelope is specific to each model of OGI camera. The operating envelope can be
developed by the owner or operator, the camera manufacturer, or a third party. The operating envelope
must be developed initially, prior to conducting surveys with the OGI camera. The operating envelope
may be updated or expanded at any time, following the procedures in this section.

8.3.2 The operating envelope must be confirmed for all potential configurations that could impact the
detection limit, such as high sensitivity modes, available lenses, and handheld versus tripod. Conversely,
separate operating envelopes may be developed for different configurations. If, in addition to or in lieu of
the display on the camera itself, an external device (e.g., laptop, tablet) is intended to be used to visualize
the leak in the field, the operating envelope must be developed while using the external device. If the

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external device will not be used at all times, use of the external device is considered a separate
configuration, and the operating envelope testing must be performed for both configurations.

8.4 Development of the operating envelope is to be performed using the test gas composition, flow
rate, and orifice diameter described in Section 6.1.2, and must include the following variables:

8.4.1 Delta-T, regulated through the use of a temperature-controlled background encompassing
approximately 50 percent of the field of view, with no potential for solar interference;

8.4.2 Viewing distance from the OGI camera to the component being imaged; and

8.4.3 Wind speed, controlled through the use of an industrial fan.

8.5 Determine the operating envelope using the following procedure:

8.5.1 Set up the methane test gas at a flow rate of 17 g/hr.

8.5.2 For this flow rate, the ability of the OGI camera to produce an observable image is challenged
by ranges of the variables in Sections 8.4.1 through 8.4.3.

8.5.3 A panel of no less than 4 observers who have been trained using the OGI camera and who have
a demonstrated capability of detecting gaseous leaks will observe the test gas release for each
combination of delta-T, distance, and wind speed. A test emission is determined to be observed when at
least 75 percent of the observers (i.e., 3 of the 4 observers) see the image.

8.5.4 Repeat the procedures in Sections 8.5.2 and 8.5.3 using either a butane test gas at a flow rate of
5.0 g/hr or a propane test gas at a flow rate of 18 g/hr.

8.5.5 The operating envelope to be used in the field for each OGI camera configuration tested is the
more restrictive operating envelope developed between the two test gases.

8.5.6 Repeat the procedures in Sections 8.5.1-8.5.5 for each camera configuration that will be used to
conduct surveys in the field.

8.6 The results of the testing to establish the operating envelope, including supporting videos, must be
documented.

9.0 Conducting the Monitoring Survey

Each site must have a monitoring plan that describes the procedures for conducting a monitoring
survey. One monitoring plan can be used for multiple sites, as long as the plan contains the relevant
information for each site. At a minimum, the monitoring plan must include the elements in this section.

9.1 The monitoring plan must include a description of a daily verification check to be performed prior
to imaging to confirm that the camera is operating properly. This verification must consist of the
following at a minimum:

9.1.1 Confirm that the OGI camera software loads successfully and does not display any error
messages upon startup;

9.1.2 Confirm that the OGI camera focuses properly at the shortest and longest distances that will be
imaged;

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9.1.3	Confirm that the OGI camera produces a live IR image using a known emissions source, such as
a butane lighter or a propane cylinder;

9.1.4	Confirm that the OGI camera can perform the delta-T check function as expected if this
function will be used meet the requirement in Section 9.2.3.

9.2	The monitoring plan must include a procedure for ensuring that the monitoring survey is
performed only when conditions in the field are within the operating envelope established in Section 8.
This procedure must include the following:

9.2.1	Description of how the viewing distance from the surveyed components, the wind speed, and
the delta-T will be monitored and how the operator will deal with changes in site conditions during the
survey to ensure that the monitoring survey is conducted within the limits of the operating envelope;

9.2.2	Description of how the operator will ensure an adequate delta-T is present in order to view
potential gaseous emissions, e.g., using a delta-T check function built into the features of the OGI camera
or using a background temperature reading in the OGI camera field of view;

9.2.3	Description of how the operator will recognize the presence of and deal with potential
interferences and/or adverse monitoring conditions, such as steam, fog, mist, rain, solar glint, extremely
high concentrations of particulate matter, and hot temperature backgrounds;

9.3	The site must conduct monitoring surveys using a methodology that ensures that all the
components regulated by the referencing subpart within the unit or area are monitored. This must be
achieved using one of the following three approaches or a combination of these approaches. The
approach(es) chosen and how the approach(es) will be implemented must be described in the monitoring
plan.

9.3.1	Use of a route map or a map with designated observation locations. The map must be included
as part of the monitoring plan, with a predetermined sequence of process unit monitoring (such as
directional arrows along the monitoring path) depicted or designated observation locations clearly
marked.

9.3.2	Use of visual cues. The facility must develop visual cues (e.g., tags, streamers, or color-coded
pipes) to ensure that all components regulated by the referencing subpart were monitored. The monitoring
plan must describe what visual cue method is used and how it will be used to ensure all components are
monitored during the survey.

9.3.3	Use of global positioning system (GPS) route tracing. The facility must document the path taken
during the survey by capturing GPS coordinates along the survey path, along with date and time stamps.
GPS coordinates must be recorded frequently enough to document that all components regulated by the
referencing subpart were monitored. The monitoring plan must describe how often GPS coordinates will
be recorded and how the route tracing will ensure all components regulated by the referencing subpart are
monitored.

9.4	The monitoring plan must include a procedure that describes how components will be viewed
with the OGI camera. In general, a component should be imaged from at least two different angles, and
the operator must dwell on each angle for a minimum of 2 seconds per component in the field of view
before changing the angle, distance, or focus and dwelling again. The procedure must discuss changes, if
necessary, to the imaging mode of the OGI camera that are appropriate to ensure that leaks from all
components regulated by the referencing subpart can be imaged.

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9.4.1 For a complex scene of components, the operator must divide the scene into manageable
subsections and dwell on each angle for a minimum of 2 seconds per component in the field of view (e.g.,
for a subsection with 5 components, the minimum dwell time would be 10 seconds). It may be necessary
to reduce distance or change angles in order to reduce the number of components in the field of view.

9.4.2 The operator may choose to reduce the dwell time for complex scenes based on the monitoring
area and number of components in the subsection as prescribed in Table 14-1, provided the manageable
subsection forthe angle fills greater than half of the field of view of the camera. Use of Table 14-1 is
optional and is not required if the operator uses the minimum dwell time in Section 9.4.1.

9.5 The monitoring plan must include a plan for avoiding camera operator fatigue, as physical,
mental, and eye fatigue are concerns with continuous field operation of OGI cameras. The OGI camera
operator should not survey continuously for a period of more than 30 minutes without taking a rest break.
Taking a rest break between surveys of process units may satisfy this requirement; however, for process
units or complex scenes requiring continuous survey periods of more than 30 minutes, the operator must
take a break of at least 5 minutes after every 30 minutes of surveying. Operators can complete tasks
related to the monitoring survey, such as documentation, during the 5-minute rest break, so long as the
operator is not actively imaging components.

Note: If continuous surveying is desired for extended time periods, two camera operators can
alternate between surveying and taking breaks.

9.6 The monitoring plan must include a procedure for documenting monitoring surveys. The
information documented must include:

9.6.1 The name of the facility, date, and approximate start and end times for each monitoring survey.

9.6.2 The weather conditions, including ambient temperature, wind speed, relative humidity, and sky
conditions at the start and end of each monitoring survey. For monitoring surveys conducted for more
than four hours, record the weather conditions every two hours.

9.7 The site must have a procedure for documenting fugitive emissions or leaks found during the
monitoring survey according to one of the following approaches. If no emissions are found, no recorded
footage is required to demonstrate that the component was not leaking.

9.7.1 If a leak is found, capture either a short video clip or photograph that depicts the leak and the
component associated with the leak. If the leak is not immediately repaired, the leaking component must
be tagged for repair. The date, time, location of the leak, and identification of the component associated
with the leak must be recorded and stored with the OGI survey records.

9.7.2 A full video of the monitoring survey must be recorded. The video must document the
monitoring results for each piece of regulated equipment. Leaking components must be tagged for repair,
and the date, time, location of each leak, and identification of the component associated with each leak
must be recorded and stored with the OGI survey records.

9.8 The monitoring plan must include a quality assurance (QA) verification video for each OGI
operator at least once each monitoring day. The QA verification video must be a minimum of 5 minutes
long and document the procedures the operator uses to survey (e.g., dwell times, angles, distances,
backgrounds) and the camera configuration.

9.9 The monitoring plan must describe the process that will be used to ensure the validity of the
monitoring data as detailed in Section 11.

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10.0 Camera Operator Training

10.1 The facility or company performing the OGI surveys must have a training plan which ensures
and monitors the proficiency of the camera operators. Training should include classroom instruction and
field training on the OGI camera and external devices, monitoring techniques, best practices, process
knowledge, and other regulatory requirements related to leak detection that are relevant to the facility's
OGI monitoring efforts. If the facility does not perform its own OGI monitoring, the facility must ensure
that the training plan for the company performing the OGI surveys adheres to this requirement.

10.2 Prior to conducting monitoring surveys, camera operators must complete initial training and
demonstrate proficiency with the OGI camera and any external devices to be utilized for detecting a
potential leak.

10.2.1 At a minimum, the training plan must include the following classroom training elements as
part of the initial training. Classroom training can be at a physical location or online.

10.2.1.1 Key fundamental concepts of the OGI camera technology, such as the types of images the
camera is capable of visualizing and the technology basis (theory) behind this capability.

10.2.1.2 Parameters that can affect image detection (e.g., wind speed, temperature, distance,
background, and potential interferences).

10.2.1.3 Description of the components to be surveyed and example imagery of the various types of
leaks that can be expected.

10.2.1.4 Operating and maintenance instructions for the OGI camera used at the facility.

10.2.1.5 Procedures for performing the monitoring survey according to the monitoring plan, including
the daily verification check; how to ensure the monitoring survey is performed only when the conditions
in the field are within the established operating envelope; the number of angles a component or set of
components should be imaged from; how long to dwell on the scene before changing the angle, distance,
and/or focus; how to improve the background visualization; the procedure for ensuring that all
components regulated by the referencing subpart are visualized; and required rest breaks.

10.2.1.6 Recordkeeping requirements.

10.2.1.7 Common mistakes and best practices.

10.2.1.8 Discussion on the regulatory requirements related to leak detection that are relevant to the
facility's OGI monitoring efforts.

10.2.2 At a minimum, the training plan must include the following field training elements as part of
the initial training:

10.2.2.1 A minimum of 3 survey hours with OGI where trainees observe the techniques and methods
of a senior OGI camera operator (see definition in Section 3.0) who reinforces the classroom training
elements.

10.2.2.2 A minimum of 12 survey hours with OGI where the trainee performs the initial OGI survey
with a senior OGI camera operator verifying the results by conducting a side-by-side comparative survey
and providing instruction/correction where necessary.

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10.2.2.3 A minimum of 15 survey hours with OGI where the trainee performs monitoring surveys
independently with a senior OGI camera operator trainer present and the senior OGI camera operator
providing oversight and instruction/correction to the trainee where necessary.

10.2.2.4 A final monitoring survey test where the trainee conducts an OGI survey of at least 2 hours
and a senior OGI camera operator follows behind with a second camera to confirm the OGI survey
results. If there are 10 or more leaks identified by the senior OGI operator, the trainee must achieve less
than 10 percent missed persistent leaks relative to the senior OGI camera operator to be considered
authorized for independent survey execution. If there are less than 10 leaks identified by the senior OGI
operator, the trainee must achieve zero missed persistent leaks relative to the senior OGI camera operator
to be considered authorized for independent survey execution.

10.2.2.5 If the trainee doesn't pass the monitoring survey test in Section 10.2.2.4, the senior OGI
operator must discuss the reasons for the failure with the trainee and provide instruction/correction on
improving the trainee's performance. Following the discussion with the senior OGI operator, the trainee
may repeat the test in Section 10.2.2.4.

10.3 All OGI camera operators must attend a biennial classroom training refresher. This refresher can
be shorter in duration than the initial classroom training but must cover all the salient points necessary to
operate the camera (e.g., performing surveys according to the monitoring plan, best practices, discussion
of lessons learned). Refresher training can be at a physical location or online.

10.4 Performance audits for all OGI camera operators must occur on a quarterly basis with at least
one month between two consecutive audits. Performance audits must be conducted according to one of
the following procedures:

10.4.1 Performance audit by comparative monitoring. Comparative monitoring in near real-time is
where a senior OGI camera operator reviews the performance of the employee being audited by
performing an independent monitoring survey.

10.4.1.1 Following a survey conducted by the camera operator being audited, the senior OGI camera
operator will conduct a survey of at least 2 hours in the same area to ensure that no persistent leaks were
missed.

10.4.1.2 If there are 10 or more leaks identified by the senior OGI operator, the camera operator being
audited must achieve less than 10 percent missed persistent leaks relative to the senior OGI camera
operator. If there are less than 10 leaks identified by the senior OGI operator, the camera operator being
audited must achieve zero missed persistent leaks relative to the senior OGI camera operator. If the
camera operator being audited does not achieve this benchmark, then the camera operator being audited
will need to be retrained as outlined in Section 10.4.3.

10.4.2 Performance audit by video review. The camera operator being audited must submit unedited
and uncut video footage of their OGI survey technique to a senior OGI camera operator for review.

10.4.2.1 The videos must contain at least 2 hours of survey footage. If a single monitoring survey is
less than 2 hour, footage from multiple monitoring surveys may be submitted; however, all videos
necessary to cover a 2-hour period must be recorded and submitted for review. The senior OGI camera
operator will review the survey technique of the camera operator being audited, as well as look for any
missed leaks.

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10.4.2.2 If the senior OGI camera operator finds that the survey techniques during the video review
do not match those described in the monitoring plan, then the camera operator being audited will need to
be retrained as outlined in Section 10.4.3. Additionally, if there are 10 or more leaks identified by the
senior OGI operator, the camera operator being audited must achieve less than 10 percent missed
persistent leaks relative to the senior OGI camera operator. If there are less than 10 leaks identified by the
senior OGI operator, the camera operator being audited must achieve zero missed persistent leaks relative
to the senior OGI camera operator. If the camera operator being audited does not achieve this benchmark,
then the camera operator being audited will need to be retrained as outlined in Section 10.4.3.

10.4.3	At a minimum, retraining must consist of the following elements:

10.4.3.1	A discussion of the reasons for the failure with the OGI operator being audited and
techniques to improve performance.

10.4.3.2	A minimum of 8 survey hours with OGI where the trainee performs the initial OGI survey
with a senior OGI camera operator verifying the results by conducting a side-by-side comparative survey
and providing instruction/correction where necessary.

10.4.3.3	A minimum of 8 survey hours with OGI where the trainee performs the survey
independently with the senior OGI camera operator trainer present and the senior OGI camera operator
provides oversight and instruction/correction to the trainee where necessary.

10.4.3.4	The audited camera operator must perform a final monitoring survey test as described in
Section 10.2.2.4 and meet the requirements in Section 10.2.2.4 to be recertified.

10.4.4	If an OGI operator requires retraining in two consecutive quarterly audits, the OGI operator
must repeat the initial training requirements in Section 10.2.

10.4.5	If a camera operator is not scheduled to perform an OGI survey during a quarter, then the audit
must occur with the next scheduled monitoring survey.

10.5	If an OGI camera operator has not conducted a monitoring survey in over 12 months, then the
operator must complete the retraining requirements in Section 10.4.3 prior to conducting surveys. If an
OGI camera operator has not conducted a monitoring survey in over 24 months, then the operator must
complete the biennial classroom training in Section 10.3 and complete the retraining requirements in
Section 10.4.3 prior to conducting surveys.

10.6	Previous experience with OGI camera operation can be substituted for some of the initial
training requirements in Section 10.2 as outlined in this Section 10.6.1 and 10.6.2.

10.6.1	OGI camera operators with previous classroom training (either at a physical location or online)
that included a majority of the elements listed in Section 10.2.1 do not need to complete the initial
classroom training as described in Section 10.2.1, but if the date of training is more than two years before
[THE DATE OF PUBLICATION OF THE FINAL RULE IN THE FEDERAL REGISTER], the
biennial classroom training in Section 10.3 must be completed in lieu of the initial classroom training in
Section 10.2.1.

10.6.2	OGI camera operators who have 40 hours of experience over the 12 calendar months prior to
[THE DATE OF PUBLICATION OF THE FINAL RULE IN THE FEDERAL REGISTER] may
substitute the retraining requirements in Section 10.4.3, including the final monitoring survey test, for the
initial field training requirements in Section 10.2.2.

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11.0 Quality Assurance and Quality Control

11.1 As part of the facility's monitoring plan, the facility must have a process which ensures the
validity of the monitoring data. Examples may include routine review and sign-off of the monitoring data
by the camera operator's supervisor, periodic comparative monitoring using a different camera operator
as part of a continuing training verification plan described in Section 10, or other due-diligence
procedures.

11.2 For each monitoring day, the daily OGI camera verification must be performed as described in
Section 9.1. Additionally, the daily QA verification video for each operator must be recorded as described
in Section 9.8 for each operator for each monitoring day.

11.3 The following table is a summary of the mandatory QA and quality control (QC) measures in
this protocol with the associated frequency and acceptance criteria. All of the QA/QC data must be
documented and kept with other OGI records.

Summary Table of QA/QC

Parameter

QA/QC
Specification

Acceptance Criteria

Frequency

OGI Camera
Design

Spectral
bandpass range

Must overlap with major absorption
peak of the compound(s) of interest.

Once initially (prior to
using the OGI camera to
conduct surveys), when
survey components on
equipment that was not
previously included in
monitoring surveys,
whenever there are
process changes that are
expected to cause the
gaseous emissions
composition to change.

OGI Camera
Design

Initial camera

specification

confirmation

Must be capable of detecting (or
producing a detectable image of)
methane emissions of 17 g/hr and
either butane emission of 5.0 g/hr or
propane emissions of 18 g/hr at a
viewing distance of 2 meters and a
delta-T of 5 °C in an environment of
calm wind conditions around 1 m/s
or less.

Once initially (prior to
using the OGI camera to
conduct surveys).

Developing the

Operating

Envelope

Observation
confirmation

Leak is observed by 3 out of 4 panel
observers for specific combinations
of delta-T, distance, and wind speed.

Once initially (prior to
using the OGI camera to
conduct surveys) and
prior to using a new
camera configuration for
which an envelope was
not previously
established. The
operating envelope may
be updated or expanded

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Parameter

QA/QC
Specification

Acceptance Criteria

Frequency







at any time, following
the procedures in
Section 8.

OGI Camera
Functionality

Verification
Check

Meet the requirements of Section 9.1
to confirm that the OGI camera
software loads successfully and that
the camera focuses properly,
produces a live IR image, and, as
applicable, performs the delta-T
check function.

Each monitoring day,
prior to conducting a
survey.

Camera Operator
Training

Classroom
training

Meet the requirements of Sections
10.2.1 and 10.3 with the issuing of a
certificate or record of attendance.

Prior to conducting
surveys (except as noted
in Section 10.6.1), with
a biennial refresher.

Camera Operator
Training

Field training

Meet the requirements of Section
10.2.2 while maintaining the records
of survey hours by the trainee along
with a certificate or record of
completion issued upon passing the
final monitoring survey test in
Section 10.2.2.4 with the date of the
survey recorded.

Except as noted in
Section 10.6.2, prior to
conducting surveys and
if retraining is required
following two
consecutive quarterly
audits.

OGI Camera

Operator

Performance

Quarterly

performance

audits

Comparative monitoring or video
review. Meet the benchmarks in
Section 10.4.1.2 or 10.4.2.2.

Every 3 months, with at
least 1 month between
consecutive audits or at
the next scheduled
monitoring survey if a
camera operator is not
scheduled to perform an
OGI survey during the
quarter.

Camera Operator
Training

Field retraining

Meet the requirements of Section
10.4.3 while maintaining the records
of survey hours by the trainee along
with a certificate or record of
completion issued upon passing the
final monitoring survey test in
Section 10.2.2.4 with the date of the
survey recorded.

After failing to meet the
benchmarks in Section
10.4.1.2 or 10.4.2.2
during a quarterly audit
or after a prolonged
period (greater than 12
months) of not
performing OGI
surveys. May be
substituted for initial
field training as noted in
Section 10.6.2.

OGI Camera

Operator

Performance

QA verification
video

Record a video that is a minimum of
5 minutes long that documents the
procedures the operator uses to
survey (e.g., dwell times, angles,

Each monitoring day.

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Parameter

QA/QC
Specification

Acceptance Criteria

Frequency

distances, backgrounds) and the
camera configuration.

12.0 Recordkeeping

12.1 Records must be kept for a period of 5 years, unless otherwise noted below or otherwise
specified in a referencing subpart. Records may be retained in hard copy or electronic form.

12.2 The facility must maintain the following records in a manner that is easily accessible to all OGI
camera operators. These records must be retained for as long as the site performs OGI surveys. Older
versions of these records that are no longer relevant because they have been replaced by newer versions
must be retained for a period of 5 years past the date on which they are replaced.

12.2.1 Complete site monitoring plan with all the required elements.

12.2.2 The OGI camera operating envelope limitations.

12.3 All data supporting the OGI camera specification confirmation (initially and updated as required
in Section 8.1) and development of the operating envelope. While the owner or operator does not need to
have a copy of these records onsite if another entity performed the camera specification confirmation or
development of the operating envelope, the owner or operator must: (1) ensure that the camera
specification confirmation and development of the operating envelope were performed in accordance with
the requirements of this Appendix K, (2) ensure easy access to these records, and (3) make the records
available for review if requested by the Administrator. These records must be retained for the entire
period that the OGI camera is used to conduct surveys at the site plus 5 years.

12.4 The training plan for OGI camera operators. The plan must be retained for as long as the site
performs OGI surveys. Older versions of the plan that are no longer relevant because they have been
replaced by a newer version must be retained for a period of 5 years past the date on which they are
replaced. If the facility does not perform its own OGI monitoring, the owner or operator must: (1) ensure
that the training plan for the company performing the OGI surveys adheres to the requirements of this
Appendix K, (2) ensure easy access to the plan, and (3) make the plan available for review if requested by
the Administrator.

12.5 For each OGI camera operator, the following records. These may be kept in a separate location
for privacy but must be easily accessible to program administrators and available for review if requested
by the Administrator. It may be necessary to retain the records in Section 12.5.3 for longer than 5 years to
show the career experience hours for senior OGI camera operators. If the facility does not perform its own
OGI monitoring, the owner or operator must: (1) ensure that the training plan for the company performing
the OGI surveys adheres to the requirements of this Appendix K, (2) be able to easily access these
records, and (3) make the records available for review if requested by the Administrator. The records
must include the following information.

12.5.1 The date of completion of initial OGI camera operator classroom training;

12.5.2 The date of the passed final site survey test following the initial OGI camera operator field
training or retraining;

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12.5.3 The number and date of all surveys performed, and if the survey is part of initial field training
or retraining, the amount of survey hours and notation of whether the survey was performed by observing
a senior OGI camera operator, side-by-side with a senior OGI camera operator, or with oversight from a
senior OGI camera operator;

12.5.4 The date and results of quarterly performance audits;

12.5.5 The date of the biennial classroom training refresher; and

12.5.6 Documentation to support the use of previous experience as a substitution for initial training
requirements, including the date of previous classroom training and documentation of survey hours over
the 12 calendar months prior to [THE DATE OF PUBLICATION OF THE FINAL RULE IN THE
FEDERAL REGISTER], as appropriate.

12.6 Monitoring survey results shall be kept in a manner that is accessible to those technicians
executing repairs and at a minimum must contain the following:

12.6.1 Daily verification check;

12.6.2 Identification of the site surveyed and the survey date and start and end times;

12.6.3 Name of the OGI camera operator performing the survey and identification of the OGI camera
used to conduct the survey. The identification of the OGI camera can be the serial number or an assigned
name/number labeled on the camera, but it must allow an operator or inspector to tie the camera back to
the records associated with the camera (e.g., maintenance, initial specification confirmation);

12.6.4 Weather conditions, including the ambient temperature, wind speed, relative humidity, and sky
conditions, at the start and end of the survey and every two hours (if the survey exceeded four hours in
length);

12.6.5 Video footage or photograph of any leak detected, or video footage of the entire survey, along
with the date, time, and location of the leak, and identification of the component associated with the leak;

12.6.6 The daily QA verification video for each operator; and

12.6.7 GPS coordinates for the route taken, if Section 9.3.3 is used to ensure all components regulated
by the referencing subpart are monitored.

12.7 Camera maintenance and calibration records over the entire period that the OGI camera is used
to conduct surveys at the site. Older versions of these records that are no longer relevant because they
have been replaced by newer versions must be retained for a period of 5 years past the date on which they
are replaced. If the facility does not perform its own OGI monitoring, the owner or operator must be able
to easily access these records and must make the records available for review if requested by the
Administrator.

13.0 References

13.1 U.S. Department of Health and Human Services. (2010). NIOSH Pocket Guide to Chemical
Hazards. NIOSH Publication No. 2010-168c. Also available from https://www.cdc.gov/niosh/docs/2010-
168c/default.html.

13.2 U.S. Environmental Protection Agency. (2021). Technical Support Document: Optical Gas
Imaging Protocol (40 CFR Part 60, Appendix K).

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13.3 U.S. Environmental Protection Agency. (2020). Optical Gas Imaging Stakeholder Input
Workshop Presentations and Discussion; Summary Letter Report.

13.4 Zeng, Y., J. Morris, A. Sanders, S. Mutyala, and C. Zeng. (2017). Methods to Determine
Response Factors for Infrared Imagers used as Quantitative Measurement Devices. Journal of the Air &
Waste Management Association, 67(11), 1180-1191. DOI: 10.1080/10962247.2016.1244130. Available
online at: https://doi.org/10.1080/10962247.2016.1244130.

13.5 Zimmerle, D., T. Vaughn, C. Bell, K. Bennett, P. Deshmukh, and E. Thoma. (2020). Detection
Limits of Optical Gas Imaging for Natural Gas Leak Detection in Realistic Controlled Conditions.
Environmental Science & Technology, 54(18), 11506-11514. DOI: 10.1021/acs.est.0c01285.

14.0 Tables, Diagrams, and Flow Charts
Table 14-1. Reduced Dwell Time (in seconds) by Subsection Area and Scene Complexity (Optional)

Components in Subsection

Monitoring
Area (m2)

2-3

4-5

5-10

10-20

>20

0.125

0.25

0.50

1.0

>1.0

* The camera operator must either reduce the subsection area, the scene complexity, or both by moving
closer to the components or changing the viewing angle.

Note: This table only applies when an OGI operator wishes to reduce the dwell time of a scene.
Normally, the dwell time for each angle must be a minimum of 2 seconds per component in the field of
view. The operator may reduce the dwell time based on the monitoring area and number of components as
described in this table, provided the manageable subsection for the angle fills greater than half of the field
of view of the camera. The operator must divide the scene into manageable subsections and image each
subsection from at least two different angles. To use Table 14-1, the depth of components within the
monitoring area must be less than 0.5 meters.

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Annex 1 to Appendix K of 40 CFR part 60 - Development of Response Factors for OGI

Cameras

1.0 Introduction

The purpose of this annex is to outline the protocol for the development of response factors (RF) for
optical gas imaging (OGI) cameras. As defined in Section 3.0 of Appendix K, a response factor is the
OGI camera's response to a compound of interest relative to a reference compound at a concentration
path-length of 10,000 part per million-meter (ppm-m).

1.1 Nomenclature.

1.1.1 The definitions listed in Section 3.0 of Appendix K apply to this annex.

1.1.2 Infrared (IR) radiance pixel area. The IR radiance pixel area is the average of a set of pixel IR
radiance for an instantaneous measurement. There will be three different areas representing the reference
cell, gas cell, and the raw blackbody surface. The pixel count for each area must be at a minimum of 1%
of the total pixels of the detector. The pixel locations selected for an area must not change throughout the
test.

1.1.3 Measurement data set. Measurement data set is the number of time independent IR radiance
pixel areas that are taken. The minimum number of measured IR radiance pixel area within a data set is
31. For a 1 Hertz device, the minimum measurement data set would be 31 seconds. The number of
measured IR radiance pixel area within a measurement data set should stay consistent throughout the test.

1.1.4 Reference Compound. The reference compound is the compound that provides the reference for
determination of the response factor with the compound of interest. The reference compound for this
annex is propane, unless otherwise specified in a referencing subpart.

2.0 Applicability and Analytical Principle

2.1 Applicability. This annex applies to the determination of compound specific response factors
through empirical testing for use with Appendix K. This annex does not apply to other applications of
OGI cameras or other instruments. This annex does not limit the use of other peer reviewed and published
techniques and response factors per Section 3.0 of Appendix K.

2.2 Analytical Principle. OGI cameras work by providing an image or video with each pixel
representing a measurement of the IR radiation. OGI cameras limit measurement to specific wavelengths
of IR through the choice of the detector and generally through the addition of a bandpass filter. Limiting
the measurement to specific wavelengths of IR allows the OGI camera to focus on a specific region of
interest in order to increase the detection capabilities of particular compounds of interest. The
combination of detector and bandpass filter, in addition to limiting the region of interest, will allow
varying amounts of IR over the specific wavelength region.

3.0 Equipment and Supplies.

3.1 Section 6.0 of Appendix K lists equipment and supplies that may be used in this annex.

3.2 Blackbody Source. A sufficiently large blackbody source capable of maintaining high emissivity,
as well as temperature stability and homogeneity.

3.2.1 The blackbody must have an emissivity of 0.95 or higher in the IR region of interest.

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3.2.2 The source emissive area must have a uniform temperature, where uniform is defined as all
points on the emissive area deviating no more than 0.1 degree Celsius (°C) from the average temperature
of the emissive area. The temperature readings must be accurate to at least 0.1 °C. The blackbody must be
able to maintain its temperature within 0.1 °C.

3.2.3 The source's surface area must be large enough to allow the OGI camera to take IR
measurements of two gas cells and allow for the proper measurement of IR radiance through the gas and
reference cell and IR radiance of the surface itself.

3.3 Test gas for each compound of interest, used for determining the response factor. The
concentration of the gas in the cylinder must be vendor certified to ± 5 percent of the cylinder tag value
and be in a balance of nitrogen. The concentration of the gas must be such that the gas cell concentration
is 10,000 ppm-m with less than 2 percent error. Alternatively, the gas standard may be produced with
dilution per Method 205 of 40 CFR part 51 Appendix M with the exception that the mid-supply gas may
be vendor certified to ± 5 percent of the cylinder tag value.

3.4 Gas Cell. A windowed gas cell that is leak tight and has the ability to flow gas through the cell.
The size of the cell should be such to allow for 10,000 ppm-m to be viewed by the OGI camera with less
than 2 percent error. The windows should be 99 percent transmissive in the IR region of interest and
deviate no more than 0.5 percent transmission over than region of interest. The cell must have associated
temperature, flow, and pressure measurements.

3.5 Reference Compound Gas Standard. Propane gas standard, unless a referencing subpart specifies
otherwise, used as the reference for determination of the response factor. The concentration of the gas in
the cylinder must be vendor certified to ± 2 percent of the cylinder tag value and be in a balance of
nitrogen. The concentration of the gas must be such that the gas cell concentration is 10,000. ppm-m with
less than 2 percent error.

3.6 Reference Cell. A gas cell for the reference compound gas standard which meets all of the
requirements in Section 3.4 of this annex.

3.7 Zero Gas. A 99.99 percent pure diatomic gas, typically nitrogen, that has no IR response from the
OGI camera, used to assess the detection level of the system and baseline response of the gas cells.

3.8 OGI Camera is the specific OGI camera that is being tested. Response factors must be determined
for each IR detector and bandpass filter combination. The OGI camera must have the ability to output the
raw IR radiance at the pixel level.

3.8.1 The combination of IR detector and bandpass filter may be consistent over several models such
that the developed RFs may be applicable to more than one model of OGI camera.

3.8.2 If the OGI camera model has exchangeable bandpass filters, more than one set of RFs may be
needed for the OGI camera model to account for the differences between filters.

4.0 Pre-test Preparation and Evaluations

4.1 Room Preparation. The room where testing will occur must be prepared by removing all

extraneous thermal sources, or at a minimum, isolating extraneous thermal sources with IR absorptive

material before any testing is conducted.

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4.2 Reference and Gas Cell Preparation. Perform leak checks on both the reference and gas cells.
Ensure that the temperatures of the cells are within 0.1 °C and that the pressure measurements are
working.

4.3 OGI Camera Preparation. Ensure the OGI camera is operating to manufacturer specifications and
able to record in raw IR radiance on a per pixel basis.

4.4 Blackbody Preparation and Verification. Prepare the blackbody by setting the temperature 10.0 °C
different than the gas and reference cell temperatures. Ensure the blackbody is working correctly by
verifying the IR radiance homogeneity of the blackbody surface with the OGI camera.

4.5 System Preparation. Ensure the alignment of the cells, blackbody source, and OGI camera are all
fixed in place and cannot deviate from their position during the testing.

4.5.1 The reference and gas cell windows must overlap the blackbody surface in a manner that
provides sufficient viewing of the blackbody surface from the vantage point of the camera.

4.5.2 The reference and gas cells should be placed sufficiently away from the blackbody surface. The
distance must be far enough to ensure that the reference and gas cells are not be heated or cooled by
the blackbody surface.

4.5.3 The OGI camera should be located at a distance such that the field of view allows the
requirements of the IR radiance pixel area to be met. Additionally, the distance must be such that it
does not nominally change the path length of the cell.

4.5.4 For both the reference cell and the gas cell, the depth of the cell and concentration of the gas
must result in a concentration 10,000. ppm-m with less than 2 percent error.

4.6 Initial System Assessment.

4.6.1 Flow zero gas through both the reference and gas cell, and ensure the gas cell temperatures are
within 0.1 °C.

4.6.2 Record the temperatures of the gas and reference cells, the blackbody surface, and the room.
Record the pressures in the reference and gas cells. Record the flowrates into the reference and gas
cells.

4.6.3 Measure the IR radiance of the reference cell, the gas cell, and the blackbody surface for a
measurement data set. Calculate the average of the IR radiance pixel area, the standard deviation of
the IR radiance pixel area, and the 99 percent confidence level of the IR radiance pixel area for the
reference cell, gas cell, and the blackbody surface for the measurement data set.

4.6.4 The detection limit for the system will be the highest 99 percent confidence level.

4.6.5 If the standard deviation of the reference cell's and the gas cell's average pixel areas of interest
have a difference greater than 5 percent, take corrective actions and repeat the assessment.

5.0 Sampling and Analysis Procedure

5.1 Flow reference compound gas through the reference cell and test gas for the compound of interest
through the gas cell and ensure the cell temperatures are within 0.1 °C.

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5.2 Record the temperatures of the gas and reference cells, the blackbody surface, and the room
temperature. Record the pressures in the reference and gas cells. Record the flowrates into the reference
and gas cells. If using Method 205 of 40 CFR part 51 Appendix M for dilution of the test gas for the
compound of interest, record the appropriate parameters required by the method.

5.3 Adjust the gas flow if the pressure in the cell is not within an inch of water of ambient pressure.
Ensure cell temperatures are within 0.1 °C of the room temperature.

5.4 Measure the IR radiance of the reference cell, the gas cell, and the blackbody surface for a
measurement data set. Calculate the average of the IR radiance pixel area and the standard deviation of
the IR radiance pixel area for the reference cell, gas cell, and the blackbody surface for the measurement
data set.

6.0 Post-test Requirements

6.1 Post-test Assessment.

6.1.1 Flow zero gas through both the reference and gas cells and ensure the cell temperatures are
within 0.1 °C.

6.1.2 Record the temperatures of the gas and reference cells, the blackbody surface, and the room.
Record the pressures in the reference and gas cells. Record the flowrates into the reference and gas cells.

6.1.3 Measure the IR radiance of the reference cell, the gas cell, and the blackbody surface for a
measurement data set. Calculate the average of the IR radiance pixel area, the standard deviation of the IR
radiance pixel area, and the 99 percent confidence level of the IR radiance pixel area for the reference
cell, gas cell, and the blackbody surface for the measurement data set.

6.1.4 If the average and standard deviation of the reference cell's and the gas cell's average pixel
areas of interest have a difference greater than 5 percent between the pre-test and post-test assessment,
then the test is invalid. Take corrective actions and repeat the test.

6.2 When the average of the IR radiance pixel areas for the compound of interest over the
measurement set as determined in Section 5.4 of this annex is greater than the detection limit established
in Section 4.6.4 of this annex, calculate the RF for the compound of interest as follows:

n „ ^Compound of Interest ~ I Gas Cell)

Rr —

Reference Compound IReference Cell)

RF = response factor of the compound of interest (unitless)

Icompound of interest average of the IR radiance pixel areas for the compound of interest over the
measurement set as determined in Section 5.4 of this annex, Wm-2sr-i.

I Gas ceii = average of the IR radiance pixel areas for the gas cell over the measurement set during the
pre-test assessment as determined in Section 4.6.3 of this annex, Wm-2sr-i.

iReference Compound average of the IR radiance pixel areas for the reference compound over the
measurement set as determined in Section 5.4 of this annex, Wm-2sr-i.

IReference Cell average of the IR radiance pixel areas for the reference cell over the measurement set
during the pre-test assessment as determined in Section 4.6.3 of this annex, Wm-2sr-i.

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6.3 When the average of the IR radiance pixel areas for the compound of interest over the
measurement set as determined in Section 5.4 of this annex is less than the detection limit established in
Section 4.6.4 of this annex, the RF is equal to zero.

7.0 Reporting and Recording Requirements

7.1 Records, including all raw data and calculations, must be kept for a period of 5 years, unless
otherwise noted below or otherwise specified in a referencing subpart. Records may be retained in hard
copy or electronic form.

7.2 All records supporting the development of RFs under this annex must be maintained in a manner
that is easily accessible to all OGI camera operators using the RFs. These records must be retained for as
long as the site performs OGI surveys with a camera model that relies on the RFs. While the owner or
operator does not need to have a copy of these records onsite if another entity performed the development
of the RFs, the owner or operator must: (1) ensure that the RF development was performed in accordance
with the requirements of this annex, (2) ensure easy access to these records, and (3) make the records
available for review if requested by the Administrator. These records must be retained for the entire
period that the OGI camera is used to conduct surveys at the site. Previous versions of these records that
are no longer relevant because they have been replaced by newer versions or because the specific OGI
camera model is no longer being used to conduct surveys at the site must be retained for a period of 5
years past the date on which the records are replaced or the OGI camera model is no longer being used to
conduct surveys at the site.

8.0 References

8.1 U.S. Environmental Protection Agency. (2021). Technical Support Document: Optical Gas
Imaging Protocol (40 CFR Part 60, Appendix K).

8.2 Zeng, Y., J. Morris, A. Sanders, S. Mutyala, and C. Zeng. (2017). Methods to Determine
Response Factors for Infrared Imagers used as Quantitative Measurement Devices. Journal of the Air &
Waste Management Association, 67(11), 1180-1191. DOI: 10.1080/10962247.2016.1244130. Available
online at: https://doi.org/10.1080/10962247.2016.1244130.

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