Abstract: ON APRIL 8,1987, SEVERAL EMPLOYEES WERE CLEANING, STERILIZING AND PACKING MEDICAL INSTRUMENTS AT THE CENTRAL PROCESSING AREA. ONE OF TWO GAS STERILIZATION UNITS, MODEL 2025, MANUFACTURED BY AMSCO, WAS BEING RUN BY EMPLOYEE #3. THE OTHER UNIT WAS NOT BEING USED. THE STERILIZER USES A GAS MIXTURE OF 12% ETHYLENE OXIDE AND 88% FREON. AT ABOUT 9 PM THAT DAY THE STERILIZER BECAME OVERPRESSURED AND RELEASED AN UNKNOWN QUANTITY OF STERILIZER GAS VIA A RELIEF VALVE. THE AREA WAS EVACUATED 5 TO 15 MINUTES LATER. INVESTIGATING EMPLOYEES #1,#5, AND #8, PLUS A MAINTENANCE EMPLOYEE DID NOT USE ANY RESPIRATORY PROTECTION DURING THEIR INVESTIGATION. EXPOSURE WAS CONFIRMED THROUGH THE USE OF A LEAK DETECTOR WHICH INDICATES THE PRESENCE OF ETO AT 10 PPM, AND DID PROVIDE SUCH INDICATION AT THE TIME OF THE LEAK. EIGHT EMPLOYEES WERE SENT TO THE EMERGENCY ROOM AND ADMITTED TO THE HOSPITAL OVERNIGHT FOR OBSERVATION. SOME TESTS WERE RUN. ALL EIGHT EMPLOYEES WERE RELEASED THE NEXT DAY. THEY SUFFERED NO HARMFUL EFFECTS FROM THE EXPOSURE.