Updated compressor vent requirements under New Source Performance Standards (NSPS) Subpart OOOOb have forced oil and gas operators to rethink how they measure, capture and report emissions. For many organizations, compliance now influences capital planning, maintenance strategy and operational risk management across compressor fleets.
As a result, operators can no longer treat compliance as a one-time technical exercise. OOOOb requires an operational discipline that integrates engineering, environmental compliance and executive oversight.
Key takeaways
- Compressors built or modified after December 6, 2022, must meet monitoring, measurement and reporting requirements*
- Annual reports are required. The first initial report deadline was set for August 5, 2025, but no annual report is due to November 30, 2026
- Measurement precision, full vent capture and defensible data management determine compliance outcomes and enforcement risk
OOOOb establishes a compliance baseline for compressor emissions
The Environmental Protection Agency’s (EPA) finalized NSPS Subpart OOOOb under the Clean Air Act to regulate methane and volatile organic compound emissions from oil and gas facilities. The rule applies to compressors constructed, modified or reconstructed after December 6, 2022.
*Centrifugal compressors located at a well site are not an affected facility, and reciprocating compressors located at a well site are not an affected facility.
The rule’s most technically demanding provisions focus on compressor seal vent emissions. According to the EPA, the regulation strengthens methane standards for new and modified sources across the oil and natural gas sector, with detailed monitoring and reporting requirements for affected facilities (see the EPA’s summary of the final rule here).
Measurement requirements that define OOOOb compliance
Centrifugal compressors must install a closed vent system, use an emissions control device or demonstrate compliance through emissions measurement. Reciprocating compressors must conduct emissions measurements to verify compliance.
For vent testing, operators must collect three one-minute flow readings per component, including dry seals, wet seals and rod packing vents. Readings must fall within 10% of each other.
Allowable volumetric flow rate limits:
- 10 standard cubic feet per minute (SCFM) per dry seal
- Three SCFM per self-contained wet seal
- Two SCFM per cylinder for reciprocating compressors
If emissions exceed thresholds, operators much complete repairs or replacements withing 90 days. Operators must also conduct measurements every 8,760 operating hours.
Four operational decisions that determine compliance success
Compliance with OOOOb depends on four critical operational decisions:
Capture the full exhaust stream: Incomplete vent capture introduces data risk. Purpose-built full capture systems improve accuracy, reduce safety exposure and limit rework.
Select fit-for-purpose measurement technology: High-flow methane measurement tools that quantify both volumetric flow and gas concentration improve defensibility and reduce variability across readings.
Build audit-ready data workflows: Vent measurements must align with EPA formatting and reporting timelines. Integrated digital systems reduce manual errors and improve inspection readiness.
Standardize documentation now: Enforcement practices continue to evolve. Detailed methodologies, calibration records and test logs provide critical protection during audits.
Together, this guidance underscore that NSPS Subpart OOOOb compliance isn’t just about checking a box, it’s about implementing smart, efficient systems that keep operators ahead of regulatory pressure while enhancing operational performance.
Immediate actions to maintain OOOOb compliance
- Review compressor inventories against applicability thresholds
- Stress-test vent measurement protocols and technology selection
- Align maintenance schedules with the 8,760-hour requirement
- Establish centralized documentation and quality control processes
- Prepare internal teams for reporting deadlines
Organizations that treat OOOOb as a strategic performance issue, not a regulatory burden, reduce enforcement risk, improve emissions transparency and position themselves for the next phase of methane regulation.