Abstract: THE PLANT WHERE THE ACCIDENT OCCURRED HAS A SEWAGE PRETREATMENT SYSTEM FOR TREATING WASTES FROM A ZINC PLATING OPERATION. IT ALSO HAS A BLOCK PHOSPHATIZING SYSTEM. THE DAY BEFORE THE INCIDENT THE LAB TECHNICIAN HAD LOWERED THE PH OF A 1390 GALLON BATCH OF WASTE EFFLUENT BY ADDING 30 GALLONS OF SULFURIC ACID TO THE TANK AND CIRCULATING THE CONTENTS. THE TECHNICIAN THEN DECIDED THAT 240 POUNDS OF SODIUM METABISULFITE ALSO NEEDED TO BE ADDED, 100 POUNDS INITIALLY, THEN 140 POUNDS IN 10 POUND BATCHES WITH THE AFFLUENT CIRCULATING. A PHLANGE ON A PUMP BROKE, SO THE TECHNICIAN SHUT DOWN THE PROCESS. THE PHLANGE WAS FIXED BY THE END OF THE DAY. ON DECEMBER 14, 1984, THE WORK DAY STARTED AT 7 AM. EVERYTHING WENT AS USUAL UNTIL ABOUT 8:15 AM. THE TECHNICIAN CHECKED THE PH OF THE EFFLUENT, ADDED THREE GALLONS OF SULFURIC ACID AND STARTED THE TANK CIRCULATOR. WITHIN MINUTES, GASES FROM THE THE PRETREATMENT TANK HAD AFFECTED EMPLOYEE #1, WHO WAS LOCATED AT THE ZINC PLATING TANKS. EMPLOYEE #2 AND EMPLOYEE #7 WERE WORKING ALONG THE WEST WALL IN THE RECEIVING AND TOOL CRIB AREA. THEY WENT INTO THE PLANT OFFICES. THE LAB TECHNICIAN WAS NOT AFFECTED, SO HE GAVE HIS RESPIRATOR TO EMPLOYEE #1 AND TOLD HIM TO GO TO THE OFFICE FOR MEDICAL ATTENTION. EMPLOYEES #1, 2, AND 3 HAD THE MOST SEVERE SYMPTOMS OF HEADACHES, DIZZINESS, SORE THROAT, A METALLIC BITTER TASTE, COUGHING SPASMS, GASPING FOR BREATH, NAUSEA AND SORE CHESTS. THE EXIT DOORS AT THE WEST END OF THE BUILDING WERE OPENED, CAUSING THE GASES TO BE DISTRIBUTED THROUGHOUT THAT END OF THE BUILDING. EMPLOYEE #3 WAS AT A HOUSING LATCH MACHINE IN THE RISER DEPARTMENT. EMPLOYEE #4 WAS AT THE 127 FOLDER MACHINE IN THE WIRE DEPARTMENT. EMPLOYEE #5 WAS A DOOR HANDLE ASSEMBLER, RUNNING THE LOCKLINE MACHINE IN THE HARDWARE DEPARTMENT. EMPLOYEE #6 WAS IN THE WIRE DEPARTMENT APPLIQUEING SCUFF PLATES. EMPLOYEE #8 OPERATED A SPOT WELDER IN THE WELDING DEPARTMENT. HE CHECKED A STORAGE AREA TO SEE IF CHEMICALS WERE LEAKING. EMPLOYEE #9 WAS A WELDER IN THE RISER DEPARTMENT. EMPLOYEE # 10 WAS BEHIND THE TOOL CRIB, TEARING DOWN PARTS. EMPLOYEES #4 THROUGH #10 EXPERIENCED A BAD TASTE IN THE MOUTH, SORE THROATS, DIZZINESS, NAUSEA, COUGHING, DIFFICULTY IN BREATHING, HEADACHES, CHEST PAINS, AND INCREASED HEART RATES.