Industrial hygiene airborne guidelines and standards have been continuously developed to control worker exposure. In 1971 the Occupational Safety and Health Administration (OSHA) adopted as a federal regulation the 1968 American Conference of Governmental Industrial Hygienists Threshold Limit Value of 50 ppm ethylene oxide (EO) as an 8-hr (TWA.) In contrast to data collected by OSHA, general industrial experience and tests conducted by industrial hygiene laboratories indicate that the standard sKc charcoal tube has poor EO collection and storage capability. Biological monitoring to measure the effects of EO exposure is not in widespread use. The major part of the EO produced in the US is used in closed-system chemical manufacturing processes, a practice dictated by the flammability and reactivity hazards associated with the chemical. Engineering changes in the facilities of producer/converters of EO have been evolutionary in nature and often related to productivity improvements and concern about explosibility and flammability.