Abstract: On May 9, 2006, an employee worked in a wastewater treatment plant and entered an equalization pipe tank, a permit required confined space. Some valves in the space had been previously left open. Normally, the valves were periodically opened to drain water, but when the water was drained, the valves were closed to prevent methane gas from leaking out. When the employee climbed down the entrance ladder, an explosion occurred followed by small flames shooting out of the valves. The employee climbed out of the space, but suffered severe burns. When the fire department arrived, they closed the valves and extinguished the flames. The employee was hospitalized.