A vacuum truck operator was in the process of unloading cold heavy crude when he noticed that the 6-inch rubber hose downstream of the blower was smoldering. The truck operator discharged his fire extinguisher on the hose, turned off the blower, and closed the truck and tank valves. Shortly thereafter the tank exploded and the truck operator was engulfed in flames. He sustained third degree burns, even though he was wearing fire retardant coveralls, and needed a skin graft.