Abstract: AT APPROXIMATELY 10 AM ON JULY 16, 1986, AN EMPLOYEE OF A CLEANING CONTRACTOR RAN INTO THE PLANT TO GET HELP. TWO EMPLOYEES RAN OUTSIDE TO THE TANK, TAKING ABOUT 1 MINUTE TO GET THERE. THEY FOUND FOUR CONTRACTOR EMPLOYEES INSIDE THE TANK. FANS WERE USED TO VENTILATE THE TANK. THE FANS RAN ABOUT FOUR MINUTES, UNTIL THE EMERGENCY UNITS ARRIVED. THE UNITS WERE EQUIPPED WITH SELF CONTAINED BREATHING RESPIRATORS. TWO MEMBERS OF THE EMERGENCY UNIT WENT INTO THE TANK AND BEGAN REMOVING THE EMPLOYEES FROM THE SLUDGE AT THE BOTTOM OF THE TANK. TWO OF THE EMPLOYEES WERE IN CARDIAC ARREST. ALL FOUR EMPLOYEES WERE TRANSPORTED TO THE HOSPITAL. TWO WERE DEAD ON ARRIVAL. ONE OTHER EMPLOYEE DIED FOUR DAYS LATER. THE YOUNGEST OF THE FOUR EMPLOYEES RECEIVED SEVERE BRAIN DAMAGE. ALL FOUR EMPLOYEES WERE EXPOSED TO A HIGH CONCENTRATION OF CHLORINE GAS.