Abstract: On May 18, 2008, Employee #1, the sole owner of a welding company, was installing piping on the top of a tank that had contained a mix of methanol, water, poultry fat, and sulfuric acid. The tank had been drained, but not flushed or cleaned. He and another worker had purged the tank with Argon prior to beginning any work. Employee #1 drilled a pilot hole in the top of the tank to take an air sample with a gad detector. After obtaining unsafe readings, they continued to purge the tank until they obtained a safe reading. Employee #1 then drilled a 3-inch hole in the top of the tank to accept a flange. While making the second tack weld to the flange, an explosion occurred, blowing off the top of the tank. Employee #1 was thrown approximately 16 ft to the concrete floor, and was killed. The other worker was transported to a hospital, where he was treated and released the same day.