EPA Announces Final Rule to Reduce Ethylene Oxide Emissions

March 15, 2024 —

On March 14, 2024, the U.S. Environmental Protection Agency (EPA) announced the final amendments to Clean Air Act standards for ethylene oxide (EtO) emitted from commercial sterilization facilities, also called commercial sterilizers. The rule applies to facilities that sterilize medical products, as well as spice, extract, dried food, and dehydrated food sterilizers.


The final rule requires strict reductions in EtO emissions from sterilization chamber vents (SCVs), aeration room vents (ARVs), chamber exhaust vents, AKA “back vents” (CEVs), Group 1 room air emissions (indoor EtO storage, EtO dispensing, vacuum pump operation, and pre-aeration handling) and Group 2 air emissions (post-aeration handling of sterilized material). In the final rule all emissions standards are percent reduction which differs from the proposed rule, which had a combination of mass emission rate and percent reduction standards. The rule also requires that Group 1 and 2 emissions operate within a Permanent Total Enclosure (PTE) such that all emission can be collected and routed to a control device.


The final rule provides a timeline for compliance that requires facilities using larger amounts of EtO must comply sooner than other facilities. This timeline in is the table that follows:

EtO UseCompliance TimeframeNumber of Facilities
Over 60 tons per year2 years28
1-60 tons per year2 to 3 years39
Less than 1 ton per year3 years21


Initial compliance for facilities that use over 100 pounds per year is demonstrated using a Continuous Emission Monitoring System (CEMS) installed and operated in accordance with the requirements of Performance Specification (PS) 19. The initial performance test must consist of the first 30 operating days after the certification of the CEMS according to PS 19. For facilities that use less than 100 pounds per year, initial compliance can be demonstrated using traditional stack testing methods such as EPA Methods 1, 2, 3, and 320. Other methods and materials may be used; however, these alternative test methods are subject to administrator approval.


Any facility that uses 100 pounds per year or more must demonstrate continuous compliance with the applicable emission standards using an EtO CEMS. Alternatively, if a facility uses less than 100 pounds per year of EtO, they may demonstrate continuous compliance by conducting annual performance tests using EPA Methods 1, 2, 3, and 320.

Because the rule has percent reduction standards, control device inlet monitoring (volumetric flow and EtO) may be required. The only exception is for SCV’s where the rule gives an option for determining the inlet by measuring/calculating the mass of EtO charged to the chamber.

For CEMS, the rule allows for time sharing an instrument similar to the requirements that were in the draft rule. A facility may time-share a CEMS among different measurement points provided that:

  • The measurement points are approximately equidistant from the CEMS,
  • The sampling time at each measurement point is at least 3 times as long as the CEMS response time,
  • The CEMS completes at least one complete cycle of operation for each shared measurement point within a 15-minute period, and
  • The CEMS meets the other requirements of PS 19.

How can Montrose help?

With our partner, Thermo Fisher Scientific, Montrose Environmental Group is fully committed to supporting companies affected by the final rule. To enable regulatory compliance monitoring, Montrose offers the proven Thermo Scientific™ EMS-10™ Continuous Emissions Monitoring System. Since our first deployment in 2019, this solution has consistently demonstrated success, instilling confidence in its performance and ensuring seamless compliance with the new regulations.

EMS-10 CEMS Features/Benefits

  • Fast, sensitive, and reliable emissions analysis with less than 1 ppb detection limits.
  • Real-time monitoring and custom alerts for proactive compliance.
  • Automated compliance reporting streamlines regulatory requirements.
  • Dedicated installation, calibration, and support services ensure hassle-free facility integration.
  • Extensive service and support network for ongoing assistance.
  • Public-facing and private websites provide easy data access and reporting.

Need help with your EtO monitoring project, or sifting through the regulations? Montrose can help. Learn more about our air quality and EtO monitoring solutions at info@sensible-edp.com or visit us at sensible-edp.com/ethylene-oxide-monitoring. Ready to see the platform? Schedule a demo with one of our experts today.