Evaluation of an Add-on Local Exhaust Ventilation System for an Ethylene Oxide (ETO) Sterilizer

Abstract

An add-on local exhaust ventilation (LEV) system was evaluated as an engineering control measure during a follow-up study of high ethylene oxide (ETO) exposures at a U.S. Army medical center. Baseline breathing zone and general area samples were collected to characterize ETO exposure, and existing general ventilation was evaluated. ETO-contaminated air was recirculated back to the sterilizer area by the air-conditioning system. This recirculation, coupled with a positive differential air pressure in the sterilizer area, caused the ETO to migrate to other areas. General area sample results ranged from 0.95 to 2.80 ppm as a time-weighted average, with peak real-time exposures greater than 50 ppm. Breathing zone sample results exceeded the Occupational Safety and Health Administration action level for nine of ten individuals sampled (7 of 10 if the lower confidence limit {LCL} is applied to the sample results), with five individuals exposed to ETO concentrations greater than the PEL(3 greater than the PEL if the LCL is applied). An off-the-shelf LEV system was installed; then samples were again collected and compared to those obtained previously. Only one breathing zone sample showed a detectable level of ETO. The LEV system was able to overcome the positive differential air pressure in the Central Material Supply and the recirculating air-conditioning system to control ETO emissions effectively.