Abstract: CRUSHED COAL TAR PITCH HAD JAMMED IN A "BRADY" CONVEYOR SYSTEM. TWO EMPLOYEES, ALONG WITH TWO FOREMEN, HAD GONE TO THE BASEMENT OF THE BUILDING AND REMOVED A SECTION OF THE PIPE. THEY WERE GOING TO INCREASE AIR PRESSURE IN THE LINE TO PURGE THE MATERIAL BY BLOWING IT OUT AT THE POINT WHERE THE PIPE HAD BEEN DISCONNECTED. THIS WAS A COMMON PRACTICE AND WAS THE SECOND TIME IT HAD BEEN DONE ON THIS SAME SHIFT. WHEN THE LINE CLEARS ITSELF THE ENTIRE BUILDING IS ENGULFED IN COAL TAR DUST. THE AREA HAD NOT BEEN CLEANED IN OVER TWO WEEKS, ALLOWING AN UNUSUAL AMOUNT OF PITCH TO BUILD UP IN THE BASEMENT. THE TWO FOREMEN (MAINTENANCE) TOLD THE TWO MILLWRIGHTS TO GO ON BREAK WHILE THEY BLEW OUT THE PLUGGED LINE. THE MILLWRIGHTS LEFT. WHILE ONE OF THE FOREMEN WAS AT THE AIR CONTROL VALVE, PRESSURIZING THE SYSTEM TO BLOW OUT THE PLUG, A CLOUD OF DUST AND A BALL OF FIRE CAME UPSTAIRS AND OUT OF THE BASEMENT. THERE WAS INSTANTLY A FLASH FIRE IN THE BUILDING. THEN A MAJOR FIRE BROKE OUT AS THE PITCH RESIDUE, WHICH WAS EVERYWHERE, BEGAN TO BURN. THE TWO FOREMEN WALKED OUT OF THE BUILDING ON THEIR OWN, WITH MOST OF THEIR CLOTHING BURNT OFF THEM. BOTH HAD SECOND AND THIRD DEGREE BURNS OVER 70% OF THEIR BODIES. THE IGNITION SOURCE FOR THE EXPLOSION AND FIRE WAS MOST PROBABLY A BROKEN INCANDESCENT LIGHT BULB.