Ethylene oxide (EtO) is used in the large-scale production of chemicals, as a fumigant in certain agricultural products, as a sterilizing agent for medical devices, and can be found in the atmosphere as a pollutant emitted from natural gas, cigarette smoke and diesel exhaust. While the mutagenic properties of ethylene oxide have been known since the 1940s, the regulatory landscape around emissions and exposure limits has evolved over time. The chemical is more harmful than believed and new air quality studies are required to better characterize the risk to communities. Current methods for measuring EtO have significant limitations, including poor sensitivity, cross-talk with other common species, high cost, and/or slow sampling interval. There is an urgent demand for a field durable (mobile or stationary), real-time system, capable of reaching ppt levels of EtO detection. We present results from the deployment of a new, real-time, EtO Picarro cavity ring-down spectrometer (CRDS) capable of detecting sub-ppb levels of EtO. The analyzer can be deployed on a bench-top and/or vehicle, and its 2 second measurement interval is ideal for correlation with weather data for accurate source attribution. The analyzer has been developed to meet indoor and outdoor air quality requirements and may be deployed near (fenceline monitoring) or far (community monitoring) from emission sources.