Abstract: Employee #1 and #2, dock workers, opened the back of a trailer. They heard a hissing sound coming from the trailer and left to notify Employee #3, their supervisor. Employee #4, a lead man, came by at about that time. One dock worker returned to the trailer with the supervisor. Approximately 15 minutes later all four employees began to feel dizzy and nauseous. Employee #3 had the trailer pulled away from the dock into the yard and hazard materials response procedures were implemented. All four employees were taken to the hospital and released since the doctor did not believe that ethylene oxide was a dangerous chemical. Three employees later felt ill again and were readmitted into the hospital and given oxygen. All employees were released the next day and prescribed bed rest.