Abstract: Employee #1, age 20, was using a right angle grinder to cut a piece of exhaust pipe held in a vise. Sparks from the grinder reached the equipment box on a maintenance truck in the adjacent stall, setting off an explosion in the box that blew off its door. It struck Employee #1 in the head and knocked him to the ground. The box contained an oxyacetylene torch that was connected to tanks on the truck. The torch had been used before the truck was brought into the shop. The valves on the torch had been left slightly open, which let the residual gas in the line bleed off into the box. The box also contained a large roll of duct tape and a rag that could have functioned as collection reservoirs for the gas.