Abstract: A central supply worker loaded the ethylene oxide (EtO) sterilizer and started the cycle. A sensor alarm light came on indicating empty tanks, and the conditioning cycle did not start. The employee pressed the RESET button, but the sterilizer still did not switch back on. Employee #1 then turned on the exhaust fan, waited 15 minutes, opened the sterilizer door, and left the area. Alarms subsequently sounded in two areas. Employee #1 went to the emergency assembly area and was sent to the emergency room for medical surveillance. He showed no symptoms and was released. There were probably trace amounts of EtO in the piping to the sterilizer that triggered the alarm to go off. The employee was an experienced worker , but he failed to notify the supervisor when the sterilizer did not work. The employee has since received retraining.