Abstract: Employee #1 had climbed onto an empty tank trailer to wash it out through the top hatch. The tank trailer was a stainless steel, chemically resistant, sparkproof, dual coated 25 lb pressure vessel #307312, rated to haul flammables. The top hatch was approximately 10 feet above a concrete pad. The vehicle had contained alcohol and the vapors ignited. The flash vented through the hatch, knocking Employee #1 off the vehicle to the ground. He sustained burns to the upper body, hands, and forearms, and a fractured leg. It appears that as Employee #1 leaned over the tank, his disposable cigarette lighter fell from his pocket through the hatch into the tank, igniting the flammable vapors. A lighter was found in two parts--one outside and one inside the tanker. There were no witnesses and the employee does not recall the accident.