Abstract: On April 13, 2004, an employee lowered a portable electric pump inside a 1,000-gallon plastic tank that contained approximately 3 inches of MIOX, a 0.5-percent bleach solution that was used for treating water. He was going to pump the remaining MIOX into an adjacent 1,000-gallon tank. There were three other coworkers in the same area including the employee's son. These coworkers suffered possible hearing loss. The employee was apparently standing on the second and third steps of a 6-foot stepladder, while lowering the pump into the 6-foot tall tank. When he turned the pump on, an explosion occurred, and the employee was killed.