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Operate a Commercial Sterilization Facility? 40 CFR Part 63, Subpart O Amendments Are Coming in 2024 with More Stringent Emission Limits & Advanced Continuous Monitoring Requirements

Posted: August 30th, 2023

Authors: Matt C. 

The U.S. Environmental Protection Agency (EPA) has proposed amendments to the National Emission Standards for Hazardous Air Pollutants (NESHAP) for Ethylene Oxide (EtO) Commercial Sterilization and Fumigation Operations (40 CFR Part 63, Subpart O) that if finalized, will require the 86 commercial sterilizers in the US to use more stringent pollution controls and advanced continuous source monitoring methods to confirm the effectiveness of the controls on regulated sources of EtO. The proposed NESHAP amendments are based on the US EPA’s recent risk and technology review (RTR) of this source category and aim to reduce EtO emissions from commercial sterilization facilities by up to 80% per year, thereby decreasing EtO exposure in nearby communities. U.S. EPA proposed to require all commercial sterilizers to comply within 18 months of promulgation and to demonstrate continuous compliance via annual performance tests and operating limits, or by using an EtO continuous emissions monitoring systems (CEMS).

You may be thinking, “Ok…we already demonstrate compliance with Subpart O through an initial performance test and continuous parametric monitoring anyway, what’s really going to change for us?”

Simply, a lot. With these amendments, U.S. EPA is telling the regulated community that they do not believe the current monitoring approach is sufficient to ensure continuous compliance with the new emissions limits. The major changes were summarized in an ALL4 article written by Mike Kendall earlier this year.

To meet the proposed new and revised emissions limits, facilities will need to install new or add-on controls to several types of air emission sources. To demonstrate compliance, EPA is proposing that facilities either use an EtO CEMS, or conduct initial and annual performance tests in conjunction with continuous parameter monitoring. The performance testing methods and procedures, as well as the CEMS performance specifications and procedures for ongoing quality assurance/quality control (QA/QC) are proposed to be significantly revised.

Revisions to the EtO CEMS performance specifications and QA/QC procedures include:

  • Removal of 40 CFR Part 60, Appendix B, Performance Specification (PS) 8 as an option for continuous monitoring on the basis being that it is not selective for EtO.
  • Proposed PS-19 in 40 CFR Part 60, Appendix B for EtO CEMS installation and initial certification requirements that addresses sampling and analytical technologies for more recent EtO measurement technologies, i.e. or specifically FTIR and Cavity Ringdown Spectroscopy.
  • Removal of 40 CFR Part 60, Appendix B, PS-9 on the basis that the underlying technology (i.e., gas chromatograph) fits within the proposed structure of PS-19.
  • Proposed QA Procedure 7 in 40 CFR Part 60, Appendix F that establishes procedures for assessing EtO CEMS data quality on an ongoing basis. Updates include the requirement to develop a written QA/QC plan that details step-by-step procedures and operations for each of the following activities:
    • Daily calibration drift (CD) checks
    • Quarterly cylinder gas audit (CGA) or Dynamic Spiking Audit (DSA)
    • Annual relative accuracy test audit (RATA)
  • Systems must achieve a minimum sampling frequency of once every 15 minutes for consistency with the General Provisions of 40 CFR Part 63, Subpart A, as opposed to once per hour as currently specified in 63.364(e) of Subpart O. Note that time shared monitoring across different measurement points is acceptable provided the time-sharing criteria for EtO CEMS in amended Subpart O are met.
  • Compliance based on a 30-day rolling average determined from the sum of that day’s average and the previous 29 daily averages, divided by 30.

Revisions to the performance testing methods and procedures include:

  • Removal of EPA Test Methods 2D, 18, 25A and California EPA Air Resources Board (CARB) Method 431, as more robust measurement technology will be needed to measure much lower EtO concentration levels required by the amendments.
  • Addition of EPA Test Methods 1 and 320 for determining the location of sample ports and for Fourier Transform Infrared Spectroscopy (FTIR), respectively.
  • Update performance test requirements to determine control efficiency for sterilization chamber vents (SCV) to complete the test under normal, representative conditions that align with Clean Air Act (CAA) National Stack Testing Guidance issued in 2009. Rather than completing the test on a chamber with no product, the testing will need to be conducted during normal sterilizer chamber conditions.
  • For all emission source types, SCV, chamber exhaust vents (CEV), aeration room vents (ARV) and room air for facilities where EtO use is at least 10 tpy, 24-hour test runs are required. For facilities where EtO use is less than 10 tpy, 1-hour test runs are required.
  • Updates to how the operating limits are established and minimum requirements for the instrumentation used for monitoring.

When we say a lot is changing for those of you applicable to the commercial sterilization NESHAP, we really do mean it. The proposed amendments to Subpart O could cause your facility to purchase new controls to achieve the proposed emissions limits, update your ongoing compliance demonstration procedures (i.e., performance testing or CEMS program), or just cause you to get familiar with CEDRI for periodic reporting purposes. By this point, you’re probably wondering when this is going to happen. The comment period on the proposed rule ended on June 27, 2023 and EPA has a consent decree deadline to issue a final rule by March 29, 2024. If the proposed timeline is finalized, facilities will be required to comply with these new requirements within 18 months of promulgation. ALL4 is tracking regulatory developments related to EtO and will summarize the requirements of the final rule when it is promulgated.

For any questions on the proposed amendments or how they will affect your facility, or for assistance updating your testing and monitoring programs, do not hesitate to reach out to Matt Carideo at mcarideo@all4inc.com or 610-422-1139.


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