Abstract: Employee #1 entered a 5,000 gallon capacity truck tank containing flammable waste including toluene, methyl ethyl ketone, and methyl chloroform, to attempt to unstick the internal anti-leak valve. He entered and exited once. At the start of the second entry, he was sitting at the dome opening with a water hose putting on gloves when the flammable vapors ignited. The force of ignition threw Employee #1 against the underside of the roof; he fell 20 ft to the concrete floor. Employee #1 sustained 3rd-degree burns over 90 percent of his body and other injuries. The probable ignition source was an unapproved shoplight that was in the tank's vapor atmosphere.