Abstract: Employee #1, of HMH Corporation, was arc welding a metal toeboard to the existing standard railings on the top of a 15 ft tall by 10 ft diameter carbon steel storage tank. He was being assisted at the top of the tank by Employees #2 through #4. A coworker was on the ground was operating a Lincoln arc welder, serial #A 666426, making fine adjustments to the heat. Employee #1 accidentally touched the 1/8 in. welding rod that was being held in the electrode holder on the tank, causing a burn hole through which hot metal slag fell into the tank. The slag ignited the methanol vapors, causing an explosion. Employee #1 died of extensive injuries to his head, chest, and abdomen. Employee #4 died of a skull fracture and brain hemorrhage. Employee #2 injured his lower left leg and right arm below the elbow and bruised his left side. Employee #3 bruised his left elbow and received a laceration and torn muscles on the lower left leg. Both were hospitalized. The coworker on the ground was not injured. Employee #1 had more than ten years experience as a welder. Employees #1, #3 and #4 had received the following hazardous training components: physical data; fire and explosion data; health data; reactivity data; spill and leak procedures; protective equipment to be used; and special precautions concerning methanol. The tank was originally 3/16 in. thick but in many places had rusted on the interior to a thickness of 3/32 in. or less.