Abstract: On December 29, 1993, Employee #1, of the Tahoe-Truckee Sanitation Agency, was working on opening the second half of the waste water treatment plant in anticipation of waste water increase during the holiday season. This process required that the influent valve on a pipe running between the oxygenation basin and secondary clarifier #2 be opened. The pipe had been empty for 3 to 4 months. Employee #1 was using an electric wrench to hoist the gate valve, which was submerged in effluent water. As the water flowed into the pipe, the stagnant, methane-enriched air escaped from the pipe and rose into the area where Employee #1 was using the electric wrench. The wrench ignited the methane and a large fireball engulfed the employee. He jumped back and rolled on the ground, putting out all the flames. The weather conditions at the time of the accident were cold (30 to 35 degrees) and dead calm. First aid was promptly administered to Employee #1. He was then transported by ambulance to Tahoe Forest Hospital in Truckee, CA. Due to the fast and proper application of first aid, he received only 1st- and 2nd-degree burns.