Abstract: On August 6, 2004, Employee #1, Employee #2, and Employee #3, who were a welder and two helpers, were welding on an oilfield well service "frac-tank" when its contents of petroleum liquids and vapors erupted into flames and the tank exploded, killing Employee #1 and causing extensive burns in Employees #2 and #3, which placed them in critical condition. It is estimated that the tank was holding 4400 gallons of crude oil, and saltwater. Gases could have been present inside the tank as a result of off-gassing from the oil mixture. The explosion and flaming oil completely destroyed the frac-tank and a nearby crewcab pick-up truck. All 4400 gallons were consumed in the fire along with the contents of the pick-up truck's gasoline tank and gas from a welding set of acetylene and oxygen. The City of Marshall, Texas Fire Marshall and the Harrison County Sheriff department responded. Employees #2 and #3 were taken to the Louisiana State University Trauma & Burn Center, Shreveport, Louisiana, and were hospitalized.