EPA is not proposing broad changes to the existing standards for currently regulated emission points and hazardous air pollutants. However, the proposal includes several targeted changes involving major-source determinations, methanol emissions, small glycol dehydrators, electronic reporting and potentially unregulated emission points.

The agency is also requesting input on whether optical gas imaging under Appendix K should be available as an alternative to EPA Method 21 for leak detection at natural gas processing plants.

EPA has extended the public comment period through August 6, 2026. The proposal has not changed current compliance obligations, and the final requirements may differ based on the approach EPA ultimately selects. Facilities subject to Subparts HH or HHH can still use this period to review how the proposed changes could affect their equipment, applicability determinations and compliance documentation.

How This Proposal Differs From OOOOb and OOOOc

The Oil and Gas NESHAP proposal is separate from EPA’s recent OOOOb and OOOOc methane rule changes.

OOOOb and OOOOc are part of 40 CFR Part 60 and primarily address methane and volatile organic compound emissions from new and existing oil and natural gas sources. Subparts HH and HHH are part of 40 CFR Part 63 and regulate hazardous air pollutants from oil and natural gas production, processing, transmission and storage facilities.

Hazardous air pollutants commonly associated with these facilities include benzene, toluene, ethylbenzene, mixed xylenes and n-hexane. EPA’s current proposal also addresses methanol emissions from certain sources.

Understanding which regulatory program applies is important because Method 21, OGI, equipment controls and reporting requirements can vary between rules.

EPA Is Proposing Limited Changes to Existing Standards

As part of its technology review, EPA evaluated existing requirements for glycol dehydrators, storage vessels with the potential for flash emissions and equipment leaks at natural gas processing plants.

The agency concluded that broad revisions to the existing standards are not necessary. Current control and monitoring requirements would generally remain in place for emission points and hazardous air pollutants already regulated under Subparts HH and HHH. Several more targeted provisions could still affect how facilities determine applicability and document compliance.

Major-Source Determinations Could Change

Under the Clean Air Act, a facility is generally considered a major source if it emits or has the potential to emit at least 10 tons per year of a single hazardous air pollutant or 25 tons per year of combined hazardous air pollutants. Oil and natural gas production sources are also subject to special statutory provisions governing how emissions from wells and associated equipment are evaluated.

EPA proposes changing the definition of “associated equipment” so emissions from glycol dehydrators and storage vessels at production fields would no longer be aggregated when determining major-source status. Instead, EPA would evaluate individual dehydrators and storage vessels to determine whether any unit qualifies as a stand-alone major source.

If finalized, this change could cause some units or facilities currently classified as major sources to be treated as area sources. Operators relying on the change would still need emissions calculations and documentation supporting the revised determination.

Certain Small Glycol Dehydrators Could Face Methanol Requirements

EPA is proposing to add methanol to the hazardous air pollutants addressed under Subpart HH.

For certain small glycol dehydrators, EPA proposes requiring a 95 percent reduction in methanol emissions or routing those emissions to a compliant flare. The agency is also requesting information on whether existing BTEX limits could serve as an appropriate surrogate for methanol.

EPA is not proposing comparable methanol requirements for dehydrators at natural gas transmission and storage facilities under Subpart HHH because facilities responding to EPA’s information request did not report methanol emissions from those units.

The proposal also includes alternative compliance equations for small dehydrators with very low inlet BTEX concentrations. EPA is considering formally adding ProMax as an acceptable alternative to GLYCalc for specified emissions calculations.

Operators with affected dehydrators should review inlet gas composition, emissions calculations, control configurations and the methods currently used to demonstrate compliance.

EPA Is Considering Two Paths for Previously Unregulated Emission Points

One of the proposal’s more complex sections involves emission points that are not currently regulated under Subparts HH and HHH.

EPA’s primary proposal would defer establishing standards for these emission points. The agency is also presenting an alternative proposal that would establish requirements for several sources, primarily at major-source processing, transmission or storage facilities.

The alternative includes potential standards for:

• Acid gas removal units
• Storage vessels without the potential for flash emissions
• Storage vessels at natural gas transmission and storage facilities
• Transport vessel loading operations
• Natural gas-driven process controllers
• Natural gas-driven pumps

requirements as a forecast of the final rule. The final outcome could be narrower or broader depending on EPA’s review of public comments and its legal interpretation of the Clean Air Act.

Method 21 Would Remain Central to LDAR Compliance

EPA evaluated advances in OGI technology and the development of Appendix K, which establishes camera performance specifications, operator training, monitoring plans, operating envelopes, auditing and recordkeeping requirements.

The agency recognizes Appendix K OGI as a development in leak detection technology. However, EPA is not proposing to replace the existing Method 21 requirements for natural gas processing plants under Subpart HH.

EPA is requesting comments on whether Appendix K OGI should be allowed as an alternative to Method 21. Unless and until EPA adopts that option in a final rule, facilities must continue following the monitoring method required by the applicable regulation.

This distinction is important for facilities subject to multiple regulatory programs. OGI may satisfy one requirement while Method 21 remains necessary under another.

Electronic Reporting Could Increase Data Visibility

EPA also proposes expanding electronic reporting through its Central Data Exchange and Compliance and Emissions Data Reporting Interface.

If finalized, the rule would require electronic submission of certain performance-test reports using EPA’s Electronic Reporting Tool format or a compatible electronic file. CEMS performance evaluations that include relative accuracy test audits would also be submitted electronically.

Notifications of Compliance Status would be uploaded through CEDRI, while semiannual compliance reports would use standardized spreadsheet templates.

These requirements could make compliance information easier for regulators to review and compare. Facilities should confirm that test reports, monitoring records and supporting documentation can be produced in the required formats without losing important site-specific information.

What Operators Can Review Now

Facilities potentially subject to Subparts HH or HHH can begin by reviewing:

• Whether the correct source category and subpart have been identified
• Current major-source and area-source determinations
• Inventories of glycol dehydrators, storage vessels and other potentially affected equipment
• Methanol and BTEX emissions calculations for applicable dehydrators
• Rule-specific Method 21 and OGI requirements
• Control-device performance records
• Performance-test, CEMS and RATA reporting formats
• Existing systems for retaining and retrieving compliance documentation

Facilities with operational data or concerns relevant to the proposal may also consider submitting comments to EPA by August 6, 2026.

The final rule may ultimately produce limited changes for many operators. Still, the proposed revisions show why hazardous air pollutant requirements, methane regulations, permits and site-specific monitoring programs should be reviewed together. A monitoring method or applicability determination that works under one program may not satisfy another.

Encino Environmental Services supports operators with regulatory applicability reviews, air permitting, Method 21 and OGI LDAR programs, engine/stack testing, CEMS evaluations and compliance documentation. Connecting regulatory requirements with actual site conditions can help facilities determine which portions of the proposal deserve closer attention.