Robust, Sensitive Cavity Ringdown Spectroscopy Detection of Trace Ethylene Oxide

As of April 2024, US EPA has announced the final National Emission Standards for Hazardous Air (NESHAP ) rules regarding ethylene oxide (EtO) for commercial sterilization facilities. The updated standards require substantial reductions in the emission of EtO due to the extremely carcinogenic nature of EtO, which poses substantive risks for both acute and chronic exposure. Due to the requirement to decrease emissions, many facilities are looking for more sensitive solutions for continuous emissions monitoring (much less than 1 ppm EtO). To address the new requirements, we developed a commercial ambient air analyzer for ethylene oxide based on Cavity Ring-Down Spectroscopy (CRDS).
CRDS is an ultra-sensitive method of spectroscopy that takes advantage of an optical cavity with kilometers of optical path length and an insensitivity to intensity fluctuations that plague direct absorption optical methods. Commercial CRDS is among the most sensitive analytical approaches for real-time continuous emissions monitoring, and we bring this unparalleled technology to bear with our more than a quarter century history in CRDS analyzer manufacturing. We achieve a lower detection limit of 1 ppb in ambient air with a simple DFB infrared laser coupled into an optical cavity via a simple field-proven design containing no moving parts with an established history of robustness. The laser is shuttered at a predetermined intensity, and the rate of intensity decay is recorded, which is inversely proportional to the absorption coefficient. The flow path is optimized for both ambient sampling and the strongly oxidative stress caused by ethylene oxide. Ultimately, our analyzer is insensitive to interfering species and represents a robust, cost-effective approach to measure trace EtO.