Abstract: ABOUT 8:15 AM ON NOVEMBER 26, 1985, EMPLOYEE #1, A MECHANIC, WAS ASSIGNED THE TASK OF BURNING OFF A BEARING RING SO THAT AN AGITATOR SHAFT COULD BE REMOVED FROM A T200 STORAGE TANK. THE TANK HAD PREVIOUSLY CONTAINED CARBON TETRACHLORIDE (CCL4) AND BENZOYL PEROXIDE (BPO). TWO OTHER EMPLOYEES AND A SUPERVISOR WERE ASSIGNED AS FIRE WATCHES. THE EMPLOYEES POSSESSED FIRE AND VESSEL ENTRY PERMITS, HAD CLEANED THE TANK, PURGED AND BLANKED ALL PIPES, COVERED ALL SEWERS, MADE GAS CHECKS AND SPARK TESTS. SHORTLY AFTER BURNING BEGAN, A FLASH FIRE, WITH DENSE SMOKE, ERUPTED, APPARENTLY COMING FROM A ONE INCH PIPE FLANGE LOCATED FIVE FEET FROM EMPLOYEE #1. EMPLOYEE #1 SUFFERED SECOND DEGREE BURNS ON HIS FACE, BACK, AND THE BACK OF HIS LEFT LEG. HIS TORCH MAY HAVE CAUSED OTHER BURNS ON HIS RIGHT FOREARM. THE EXACT CAUSE OF THE FIRE IS NOT KNOWN. IT IS POSSIBLE THAT BENZOYL PEROXIDE VAPORS MAY HAVE, AT SOME EARLIER DATE, LEAKED FROM THE FLANGE AND IMPREGNATED THE PIPE INSULATION. WHEN BPO DRIES IT LOOKS LIKE INSULATION, CANNOT BE DETECTED BY A GAS CHECK AND IS SHOCK SENSITIVE. IT ALSO IS QUICKLY REDUCED TO A FLAMMABLE VAPOR WHEN HEATED. IT IS ALSO POSSIBLE THAT CARBON TETRACHLORIDE REACTED WITH A NITROGEN BLANKET TO FORM NITROGEN TRICHLORIDE, WHICH IS ALSO SHOCK SENSITIVE.