US-based sterilization facilities using ethylene oxide (EtO, EO) must comply with the 2024 update to the “Commercial Sterilizer NESHAP” (40 CFR 63, Subpart-O) in 2026-2027. Many  facilities worry that it is not possible to achieve the up to 99.99% EtO destruction removal efficiency (DRE) needed to meet the rule’s site-wide emissions limitations (SWEL). This case study, which summarizes a more detailed white paper entitled "Guaranteeing Subpart-O EtO SWEL1 and SWEL2 Compliance1 with LESNI EO CAPs and Picarro CEMS," outlines how two facilities comfortably met DRE compliance requirements using a combination of LESNI’s highly effective EO Catalytic Abatement Plants (CAPs) and Picarro’s Continuous Emissions Monitoring System (CEMS).