The fireball expanded, rose upward, and blew open the roof of the building (Figure 13). A contractor was
on the roof, having just finished testing emissions19 at furnace 4 and was moving his equipment to furnace
5, when the explosion occurred. As recorded in CSB interviews, he heard a boom, was knocked down as
the roof panels beneath his feet heaved upward, and saw flames erupt through the roof. The contractor
ran east approximately 200 feet, descended at ladder and attempted to call 911. He was not seriously
injured.