US EPA Methane Rules and Dry Gas Seals: A 10 scfm Limit per Seal

The U.S. Environmental Protection Agency (EPA) has considered dry-gas centrifugal compressors to be low emissions and not subject to control. The final regulation issued in 2023 (NSPS OOOOb) has changed that.

New points in the regulation.

The EPA acknowledges that some dry-gas compressors emit more emissions than ever thought. The regulation sets a maximum leakage flow limit of 10 scfm (standard cubic feet per minute) per dry-gas compressor, and requires monitoring and repairs to keep the flow below this level. With oil-gas compressors, the regulation requires a 95% reduction in methane and VOC emissions from the de-gasing system, or applies corresponding limits.

The timeline has changed.

On July 31, 2025, the EPA issued a provisional regulation extending several compliance markings, many of which were moved to January 22, 2027, and completed this regulation in December 2025.

Meaning for the operator.

• Dry gas leakage is still a low-emission option but leakage flow needs to be measured and monitored.
• Good operation and maintenance are conditions for reaching the limit.
• The trend of narrowing methane emissions deserves operators in many countries to follow.

This is a U.S. regulation, not directly applicable in Vietnam, and its effect may have changed after the time of the article.

Source of reference.

EPA (request summary 12/2023, announcement 12/2025), Federal Register (3/12/2025), Compressortech2.