Effective Controls for Ethylene Oxide—A Case Study

Abstract

Abstract The National Institute for Occupational Safety and Health (NIOSH) has studied the control of ethylene oxide (EtO) exposures associated with hospital sterilizers to determine which combinations of control measures are most effective. This case study describes the evaluation of controls at one hospital. The hospital had a gas sterilizer which used a mixture of EtO (12 percent by weight) in Freon-12[rgrave]. The sterilizer was retrofitted with the manufacturer's control system consisting of a ventilated air gap, local exhaust ventilation above the sterilizer door, and cycle modifications for additional end-of-cycle air flushes. Personal and area samples for EtO were collected with charcoal tubes for laboratory analysis (NIOSH method #1607) and in gas sampling bags for on-site analysis with a portable gas chromatograph. The area in front of the sterilizer was also monitored with an infrared analyzer. All full-shift personal exposures and area concentrations were less than 0.05 ppm. Infrared monitoring showed no potential exposure in front of the sterilizer due to the purge cycle or opening the door a few inches for 15 minutes prior to transferring the load to an aerator. The EtO emitted during the post-sterilization chamber evacuation cycles was controlled by isolating all but the front of the sterilizer in an adequately ventilated recess room. The ventilation rate compared favorably with three design criteria. The airflow created by the slot hood above the sterilizer door controlled emissions from the sterilizer when the door was opened a few inches, consistent with a design equation for a flanged slot. General ventilation was not an important factor in this control strategy. Additional control measures were needed to deal with possible occasional and/or incidental exposures to potentially high concentrations of EtO. Mortimer, V. D.; Kercher S. L; O'Brien, D. M. Effective controls for ethylene oxide—a case study.