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Leak detection and repair (LDAR) rules under both state and federal programs allow the use of optical gas imaging (OGI) technology. This technology has benefits over traditional monitoring practices and can be very beneficial for optimizing industrial operations. This technology is also used by those outside of industry (including regulatory agencies and non-governmental organizations). Having a solid understanding of the technology and how to use it correctly is critical to avoid misinterpreting data for maximizing the benefits this technology has to offer.

NSPS OOOOa - LDAR for Well Sites and Compressor Stations

New Source Performance Standard (NSPS) Subpart OOOOa1 has had a significant impact on the oil and gas industry because it was the first federal rule of its kind to prescribe LDAR for oil and natural gas well sites and compressor stations. Although the U.S. Environmental Protection Agency (EPA) attempted (via a 90-day stay) to delay some of the heavy-hitting requirements of the rule, NSPS OOOOa remains on the books largely intact as published in the Federal Register on September 18, 2015.

On June 12, 2017, EPA proposed a two-year stay of the LDAR provisions for well sites and compressor stations, but the stay has not been acted upon. This means that, despite the back-and-forth in 2017, the OGI survey requirements (including recordkeeping, reporting, and repairs) remain in place and have been required since June 3, 2017, with only minor changes that were finalized in 2018.

EPA and states with state-level LDAR programs often allow the use of OGI technology for compliance with the LDAR requirements for well sites and compressor stations; however, it has yet to be used on a widespread basis to quantify the amount of leaking gas. Under the right conditions, OGI technology can be used to identify leaks from components that otherwise would be considered “difficult to monitor” or “unsafe to monitor.” However, the concept of what precisely qualifies as “the right conditions” is an evolving issue: as part of the required NSPS OOOOa annual report, EPA requires reporters to include the meteorological conditions during the survey, including maximum wind speed and temperature,2 as EPA considers these two elements critical to determining at what distance an OGI camera can reasonably detect a leaking component.3

Benefits of OGI Technology Beyond Compliance

While the capital cost for a camera is not insignificant (in today's market, costs for OGI cameras can exceed $100,000), OGI technology allows operators to survey facilities more quickly than using more traditional leak detection technology (i.e., Method 21), therefore requiring fewer personnel hours than what could otherwise be required for a typical leak detection survey.

OGI technology can also be used for other applications to maximize operational efficiency. For example, it can be used to determine if thief hatch seals on storage tanks are deteriorated or if a newly installed component is operating correctly. Routine OGI inspections can assist operators in determining at what frequency certain components may need to be replaced and in defining appropriate Periodic Maintenance (PM) schedules for those components. In addition, OGI monitoring can be tremendously helpful in determining the efficacy of piping and closed vent systems. The number of uses for OGI technology continues to increase every year.

OGI Drone

Aerial Monitoring and OGI

Unmanned aerial systems (aka UAS or drones) have a wide range of applications, including several in the environmental field. Some of these uses are obvious, such as visual inspections of hard-to-reach equipment. However, UAS monitoring, coupled with OGI technology, can also greatly simplify leak detection surveys. One advantage: aerial monitoring can reduce the number of components considered “difficult to monitor” or “unsafe to monitor” - which can reduce burdensome tracking and repair requirements. Another advantage: UAS data collection can be used to monitor components that might otherwise require expensive rental equipment to reach. By employing a drone to collect such data, facilities can access hard to-reach or hazardous locations without putting personnel at risk as well as address vertical resolution. Specialty drones equipped with OGI cameras are currently available for these purposes; however, currently there is no indication that EPA intends to accept monitoring performed in this manner. It is worthwhile to note that while this type of monitoring can be very useful by reducing burdensome recordkeeping requirements and saving on the cost of renting man-lifts or other equipment, it does not - in and of itself - provide an EPA-approved monitoring method that replaces hand-held OGI cameras used for NSPS OOOOa compliance.

OGI photo1-2-3

Agencies, Non-Governmental Organizations, and OGI Technology

Although the upfront costs associated with OGI technology are relatively significant, the technology is widely available for purchase by nearly anyone within the United States; however, while almost anyone with means can purchase an OGI camera, they may not be trained to use the camera appropriately. OGI cameras see leaks, but they also see heat signatures and gas that is vented from permitted vents. Used without appropriate training and understanding of the capabilities of the device, OGI technology can generate still images or videos that may look alarming but are not actually indicative of leaks or noncompliance.

Agencies with extensive oil and gas operations in their purview likely use OGI cameras during inspections. For example, the Texas Commission on Environmental Quality (TCEQ) uses this emerging technology extensively, and TCEQ inspectors routinely arrive on-site at oil and gas facilities with an OGI camera in-hand. In addition, both EPA and state agencies mount OGI cameras on helicopters in order to survey large areas of land and large numbers of sources.4 How agencies use the information collected varies, however. The North Dakota Department of Health has requirements in statewide Consent Decrees and air quality rules5 that specifically prohibit any leaks to the atmosphere; therefore, information collected via OGI can potentially show non-compliance with those state-level consent decrees or applicable regulations. TCEQ often uses findings from OGI cameras at oil and gas sites as a screening tool to assist facilities in repairing leaks that otherwise may have gone undetected. Other states-such as Colorado, Wyoming, Ohio, and Pennsylvania-have robust state-level LDAR programs that allow the use of OGI technology.

Non-governmental organizations (NGOs) are also using the technology to highlight emissions from the upstream and midstream sectors. One such example is the Oil and Gas Threat Map, a collaborative effort between Earthworks, Clean Air Task Force, and FracTracker Alliance.6 This interactive map includes, among other things, OGI videos of various oil and gas sites throughout the United States. While the videos do show some sites with leaks visible in the OGI camera, the videos also show streams that-to the untrained eye-look like excess emissions, but are actually heat signatures from engine exhaust stacks or other interference. Those streams can look very dramatic in the recorded videos, even though they are not uncontrolled gas releases and may not be unauthorized emissions at all.

Leaks versus Vents: Knowledge is Power

As noted above, while OGI cameras are effective at detecting emissions, the fact that a gas stream is visible using OGI technology does not mean that there is an unauthorized emission requiring repair or resulting in non-compliance with permit limits or other requirements.

NSPS OOOOa differentiates fugitive emissions from gas venting due to normal operations. A stream may be visible using an OGI camera and come from a device that vents gas as part of its normal operation, and thus is not a fugitive emission. Additionally, many of the other streams may be legally permitted emissions sources venting at compliant levels.

Without detailed context, there is no way to know the difference between unlawful emissions and permitted sources simply from an OGI image or video. Therefore, it is becoming increasingly important that someone with knowledge of OGI technology, and how it is used, review the system operations and images and determine whether the captured images depict actual incidents of non-compliance or permitted sources and/or allowable vents. Working with agencies during inspections to delineate between leaks and vents is becoming increasingly critical. These determinations often cannot be made without the direct involvement of the operator because they require information about the systems that is known only by personnel with deep knowledge of the site's operation.

2019 and Beyond - Living in a World with Visible Gas Emissions

Whether required by a federal rule or employed by a state or other agency, OGI technology to find leaks from a wide variety of facilities will continue to be used in 2019 and beyond. OGI can be a useful tool in evaluating overall performance and reliability, and a powerful tool to develop appropriate periodic maintenance schedules for specific pieces of equipment (such as seals on thief hatches).

Because the technology is widely available, however, operators will continue to face the challenges resulting from inexperienced camera operators using the technology during inspections or from the fence line, and the possible mischaracterization of streams seen through the camera. Operators that use OGI technology internally should conduct regular “refresher” training to ensure that the users understand the nuance of permitted vents versus leaks. If using a third-party vendor to conduct OGI surveys, consider routinely reviewing their survey practices to ensure that users understand the details in the company's Monitoring Plan.


140 CFR Part 60
240 CFR Part 60.5420a(b)(7)
3EPA's Draft Technical Support Document - Optical Gas Imaging Protocol 40 CFR Part 60, Appendix K
4TCEQ Central Area Director Susan Jablonski, P.E. and TCEQ Director, Enforcement Division, Bryan Sinclair, Oil and Gas Environmental Conference, November 28, 2017
5Chapter 33-13-07-01
6The Oil and Gas Threat Map: