Abstract: On or about January 28, 1993, Employee #1, a contract welder, was repairing and replacing flanges on storage tanks in order to install a closed ventilation system. The storage tanks contained sodium sulfide, which reacts with acid to generate hydrogen sulfide gas. This highly flammable gas accumulated in a vapor space. Prior to the accident, a tank flashed while being cut or welded into by the employee. When a lighted torch was brought in proximity, the tank ruptured. Employee #1 died. Employee #2 had gone up on a tank to tell Employee #1 not to cut into the tank when the tank exploded. Employee #2 was hospitalized.