Leak Detection and Repair (LDAR) programs have long been associated with major sources at large chemical plants and refineries, but that distinction is rapidly disappearing. Today’s regulatory environment, especially after the rescission of the “Once In, Always In” (OIAI) policy, has reshaped how both EPA and state agencies view fugitive emissions at smaller operations. As facilities work to lower their potential to emit (PTE) to move from major to area source status, regulators are paying closer attention to whether fugitive emissions are being quantified accurately. Without an LDAR program in place, fugitive emissions can easily become the difference between qualifying as a minor source or triggering major source requirements.
The U.S. Environmental Protection Agency (EPA) has repeatedly emphasized that fugitive emissions represent a substantial portion of total facility emissions. Fugitive emissions accounted for approximately 27% of all air emissions as reported in the 2023 Toxic Release Inventory (TRI). Without properly quantifying fugitive emissions, PTE calculations can vastly underestimate total emissions from a source. For volatile organic compound (VOC) emissions, fugitive emissions must be included in PTE calculations for any of the 28 listed categories under the Prevention of Significant Deterioration (PSD) program, which includes, but is not limited to, petroleum refineries, chemical plants, and cement manufacturing. Fugitive emissions must also be quantified for all facilities when calculating PTE of hazardous air pollutants (HAPs) for NESHAP/MACT applicability. This applies to sources that are not on the list of 28 as well. For many facilities that operate process equipment in VOC or HAP service, fugitive emissions can result in the facility becoming a major source and subject to additional regulatory requirements.
The challenge for sources without actual monitoring data is that EPA guidance for estimating fugitives requires the use of conservative emission factors. In the absence of LDAR monitoring, facilities must default to emission factors EPA developed decades ago from data collected at a limited number of facilities. These average factors are based on assumed leak frequencies; thus, they can significantly overestimate actual emissions, which can result in a facility’s PTE exceeding the major source threshold. As a result, facilities may trigger major source permitting or NESHAP applicability, pay higher emissions fees and face more stringent requirements.
A well designed LDAR program provides a way to bring PTE numbers back into alignment with reality. Whether using audible, visual, and olfactory (AVO) inspections, Method 21 using portable gas analyzers, or optical gas imaging (OGI), LDAR data replaces broad assumed leak rates with actual measured conditions, yielding more accurate fugitive emissions inventories. EPA’s LDAR Best Practices Guide documents how routine monitoring identifies leaks that would otherwise go undetected and significantly improves emissions accuracy. This benefit is not just theoretical: EPA’s enforcement findings repeatedly show that facilities without LDAR monitoring often report emissions far below the methods EPA considers valid for actual emissions without monitoring. In EPA’s 1999 Enforcement Alert on fugitive emissions, it was found that leaks at some facilities were up to 10 times higher than reported when proper monitoring wasn’t performed. This discrepancy is frequently enough to trigger inspections, enforcement actions, and corrective measures, even at minor sources that believed they were compliant.
These risks are amplified as facilities grow, add equipment, or increase throughput. A site that begins as an area source can drift unknowingly into major source territory if fugitive emissions estimates are not carefully updated and verified over time. Many enforcement cases begin after an inspector discovers that a facility has exceeded major source thresholds through underestimated fugitives, sometimes for years, resulting in retroactive noncompliance with major source rules. Some regulations such as CMAS with visual inspections may not result in the appropriate emission reductions to remain an area source.
Regulatory trends further reinforce the need for LDAR at minor sources. While most LDAR requirements were historically aimed at major sources, several federal rules now apply certain LDAR obligations to area sources, including 40 CFR Part 63, Subpart VVVVVV (Chemical Manufacturing Area Sources, or CMAS) and certain regulations such as 40 CFR Part 63, Subpart BBBBBB for gasoline terminals and 40 CFR Part 60, Subparts OOOO/a/b/c for oil and gas operations. These programs include equipment inspection, leak prevention, and in some cases monitoring requirements that resemble traditional LDAR programs. Moreover, EPA’s January 22, 2025, CMAS technology review proposal makes LDAR even more relevant for minor sources. EPA has proposed adding Method 21 monitoring for equipment leaks and heat exchange systems at area source chemical manufacturing facilities, along with fenceline monitoring for ethylene oxide (EtO). These changes would bring minor source LDAR obligations closer to major source standards and reflect a broader trend toward controlling fugitive emissions regardless of source size.
Many state permitting authorities incorporate LDAR expectations into minor source permits through work practices, VOC controls, or state implementation plan (SIP) requirements. In ozone non-attainment areas, even small facilities may be required to implement fugitive emission controls as part of broader VOC reduction strategies. These state requirements often capture sources that fall below federal applicability thresholds, making LDAR an increasingly common condition of minor source permits.
Even without an explicit LDAR requirement, facilities must still quantify fugitive emissions for construction permitting, Title V applicability determinations, annual emissions inventories, and NESHAP applicability screening. When fugitive emissions are not monitored, facilities may unknowingly be out of compliance with permit terms and regulatory classifications. This is especially true for facilities that rely on historical, outdated equipment counts, engineering estimates, or site-specific emission factors.
The good news is that LDAR programs provide both compliance protection and operational benefits. Measured leak data typically results in lower calculated emissions than average factor, helping facilities maintain area source status and avoid unnecessary regulatory burdens. LDAR also reduces product loss, identifies maintenance issues early, enhances worker safety, and demonstrates to regulators that the facility is taking proactive steps to manage emissions. Combined, these advantages make LDAR not just a regulatory tool but a smart business decision, particularly for facilities that handle VOCs or HAPs in any significant quantity.
As EPA continues expanding LDAR expectations into the minor source space through rules like CMAS, MACT BBBBBB and NSPS OOOO/a/b/c, and as enforcement trends highlight the risks of mismanaged fugitives, the message is increasingly clear: LDAR programs are not only for major sources. For many facilities, they are becoming an essential part of accurate emissions reporting, informed permitting, and long-term compliance strategy.
If you’re a minor source with VOC or HAP containing process equipment, an LDAR program may be the single most effective step you can take to ensure both regulatory compliance and operational reliability, long before an inspector arrives to ask how your fugitive emissions were calculated.
Related Training
Trinity Consultants’ Leak Detection and Repair (LDAR) team has extensive experience in LDAR program implementation and quantification of fugitive emissions. Whether you need to implement a program from scratch, perform fugitive emission calculations, or review an existing program, we can help every step of the way. For more information, please contact Eric Reidy, Manager of LDAR Service at 334.531.3658 or visit TrinityConsultants.com to learn more.
