In 2016, ethylene oxide (EtO) was determined to have a 100 in a million mutagenic risk factor for a lifetime of continuous exposure at 11 parts-per-trillion by volume (11 pptv or 0.02 ug/m3) by the U.S. EPA. Currently, techniques to quantify ethylene oxide at less than 11 pptv in ambient air are scarce. This SBIR will develop the key components required to ethylene oxide measurements in ambient air with limits of quantitation at less than 11 pptv in less than 5-minute measurements. The Rapid EtO analysis capability will be a significant innovation to our existing AROMA-ETO platform which already delivers MQL < 10 pptv but in 30 minutes. This platform utilizes highly selective, cavity ring-down spectroscopy, sample pre-concentration, and chromatographic separation to achieve single digit parts-per-trillion detection limits. This technique has shown proven sensitivity and selectivity in complex matrices such as ambient air with high concentrations of water and other VOCs which is unmatched by other ambient monitoring technologies currently on the market for ethylene oxide. This project will drive key innovations to accelerate measurements timescales for EtO to speeds that ensure optimal spatial (mobile monitoring) and temporal resolution (mobile or stationary monitoring), technological feasibility will focus on the reduction in the front-end gas handling system. Immediate applications include ambient monitoring for ethylene oxide by regulatory air quality agencies, chemical manufacturers or commercial sterilizers, and communities. The ease-of-use and low infrastructure and consumables requirements enable the technology to be utilized by a wide variety of end users. We estimate that the potential market size for this technology in ambient air monitoring alone is over $20 million dollars in the next 5 years. Utilization of this technology for industrial environmental health and safety monitoring or fenceline/leak detection is also possible. The development of a robust, fast, and sensitive monitoring technique for ethylene oxide is critical to inform regulators, industry, and communities of ambient exposure risk. This technology can be utilized by all groups for stationary or mobile monitoring to better inform us about background ethylene oxide in the ambient environment and release events.