Abstract: Employee #1 was welding on a 100 gallon diesel fuel tank. He had purged the tank with a non-combustible gas, either argon or nitrogen, prior to welding. The employee tested the tank after welding and found a small pinhole. He struck an arc on the tank and the fuel tank caught fire and exploded. He had not purged the tank a second time. Employees #2 and #3 were burned trying to put out the fire that engulfed Employee #1. He was fatally injured and the other two employees were seriously injured. Employee #2 received burns on her hands and arms. Employee #3 received burns on his hands, face, ears, and back. The burning ceiling fell on Employee #3 before he was completely out of the fire area.