Abstract: On May 2, 1994, Employees #1 and #2 were assigned to change gas cylinders at an acute care hospital where on-site sterilization of surgical instruments is conducted using ethylene oxide (EtO) gas mixed with freon. When Central Services called Plant Management to change the EtO cylinders only, Employees #1 and #2 thought there was a mistake in the request and responded to the site to change tanks. They were not trained in the procedure for changing EtO tanks. Two attempts were made to turn off the tanks to remove them from the area before the two employees stated that they did not have the proper tools to remove the tanks. They learned of their exposure from the Central Service Manager after she heard alarms sounding in the main hall and entered the area to inform all employees to leave. Employees #1 and #2 were exposed to EtO gas through inhalation and skin absorption. They were sent to the county emergency room for treatment and documentation of exposure after reporting the incident to their supervisor.