June 22, 2026

Amendments Finalized for Chemical Manufacturing Area Sources NESHAP

New amendments for the chemical manufacturing area sources (CMAS) NESHAP took effect on April 1, 2026. [91 FR 16502] The amendments were finalized mostly as proposed with minor technical corrections. The changes to Part 63, Subpart VVVVVV are expected to result in a reduction of hazardous air pollutant (HAP) emissions by 160 tons per year (tpy) and volatile organic compound emissions by nearly 1,600 tpy. Notably, the agency chose not to finalize the originally proposed ethylene oxide (EtO) emission standards, stating it “intends to coordinate a final action on this issue with the regulation of EtO from major sources of HAP.” [91 FR 16503] However, EPA recently recinded new EtO standards at major and area source commercial sterilizers (see our previous article). Changes to the CMAS NESHAP include:

Removing a pressure vessel exemption from the definition of “storage tank”, and a no detectable emissions requirement for pressure vessels;
Monitoring, preventative measures, and root cause analysis for pressure relief devices in organic HAP service;
A prohibition on bypassing air pollution control devices for closed vent systems;
Initial and periodic performance testing for certain process vents and storage tanks;
Eliminating the affirmative defense provisions (see our previous article on affirmative defense); and
Electronic reporting via EPA’s compliance and emissions data reporting interface (CEDRI).

Minor changes were made to the Subpart VVVVVV applicability criteria. While the definitions of a new and existing source have not changed, sources have updated compliance deadlines for the new provisions promulgated under this final rule. [§63.63.11494(i)]

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