Abstract: At 7:00 a.m., Employee #1 arrived at work and was told by his supervisor to fix a hose on a trailer. He fixed it and was then told to take tanker trailer #33 into the garage and replace the leaking O-rings on valves #1 through #3. This trailer , which was used primarily to haul flammables or combustibles, had four separate compartments and a vapor recovery system. The trailer had been unloaded the day before and was considered empty, but when Employee #1 opened the valves, about a cup of liquid ran out of valve #3. Employee #1's supervisor informed him that methyl ethyl ketone had been in one of the compartments but did not tell him what had been in the others. Employee #1 had difficulty removing the six Allen screws from the housing around the O-rings, finding that the screws were possibly frozen or rusty. He tried using lubricating oil and tapping on the housing but to no avail. He then got an oxyacetylene torch and proceeded to heat the Allen screws. He had removed one and was beginning to heat another when he heard air rushing up the valve. There was an explosion and Employee #1 was knocked to the floor and killed. Employees #2 through #5 were hospitalized.