May 19, 2026

Polyether Polyol Production NESHAP Receives Significant Updates

New provisions for the polyether polyols (PEPO) production NESHAP took effect on March 18, 2026. [91 FR 13116] EPA’s final rule fulfill’s its technology review obligation under CAA Section 112(d)(6) [42 U.S.C. Section 7412(d)(6)], and the agency chose not to finalize the proposed 2024 second risk review [89 FR 105986] under CAA Section 112(f)(2) [42 U.S.C. Section 7412(f)(2)]. See our previous article discussing EPA’s new stance on risk and technology reviews (RTRs). The rule primarily establishes new ethylene oxide (EtO) standards, updates maximum achievable control technology (MACT) requirements, and addresses issues raised in an administrative petition for reconsideration stemming from a 2014 RTR [79 FR 17340].

New provisions in Part 63, Subpart PPP begin with EtO emission limits and standards for equipment “in EtO service.” “In EtO service,” lengthily defined in 63.1423(b), broadly includes equipment that is in contact with a liquid or gas that is ≥1%wt EtO. Regulated equipment and materials include heat exchanges, process vents, storage vessels, wastewater, and equipment leaks, and are subject to varying emission limits and monitoring, repair, and control obligations. The originally proposed EtO fenceline monitoring program was not finalized.

The specific MACT standards vary depending on the polyether polyol manufacturing process unit (PMPU) and material, but include:

The use of the Modified El Paso Method [incorporated by reference at §63.14(u)(1)] for heat exchange system monitoring;
Lowered applicability and control thresholds for batch process vents, storage vessels, and equipment leaks for valves in gas/vapor or light liquid service;
Vapor balancing or reduced emissions for certain transfer operations; and
Periodic performance testing for process vent control devices.

Many additional changes were finalized, including an expansion of the affected source to cover specific reactions after epoxide polymerization is complete and an annual applicability determination for non-PMPUs that once produced a polyether polyol. New affected sources must be in compliance with the provisions upon initial startup or March 18, 2026, whichever is later, while existing sources must achieve compliance upon initial startup or March 18, 2029, whichever is later.

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