Abstract: At approximately 12:30 p.m. on April 29, 1997, Employees #1 and #2 were replacing the meter leveling gauge on the roof of standard denatured alcohol (SDA) tank #2. The 20 ft tall tank contained 6,033 gallons of ethyl alcohol, a class IB flammable liquid. They disconnected the wiring to the explosion-proof metering device and placed it on top of the tank. As they removed the metering device from the tank roof, ethanol vapors escaped and traveled along the roof of the tank because ethanol is denser than air. When the ethanol vapors reached the live wires to the metering device several feet away, they ignited and flashed back into SDA tank #2. The resulting explosion propelled Employee #1 approximately 50 yards northeast. He landed on a cement side street and died on impact. Employee #2 landed on grass approximately 10 yards northeast; he sustained a concussion and multiple injuries. Neither of the employees nor management had performed lockout/tagout procedures on the electrical wiring to the metering device that was being removed.