Abstract: At 9:45 a.m. on July 18, 2007, Employee #1, a dive instructor working at a not-for-profit college of oceanography and engineering in San Diego suffered serious injury when a valve on a high pressure oxygen line caught fire and exploded. The worksite where the accident occurred is a facility where students are trained to be commercial divers. The business includes several buildings which are currently being built or remodeled by a General Contractor. The building where the accident occurred was a new building that the college had occupied on July 9, 2007, although there was still some items being completed at the time of the accident. A subcontractor was doing some finishing work on the gas piping systems. The oxygen line was connected to a hyperbaric chamber that is used in instruction activities. Employee #1's job that day included working with another instructor to set up the oxygen system for a class demonstration. The oxygen system had been online once about two weeks prior to the accident for pressure testing, but had not been used since. Employee #1 went downstairs to an exterior covered storage area where the compressed air tanks and gas cylinders were stored. There were three oxygen cylinders connected to a manifold. Employee #1 opened up one of the cylinders and noted the pressure, then opened up another small metering valve on the manifold. He then reached up to the last valve in the line which was a quarter turn ball valve. Just as he opened the valve he heard a "pop" and the valve exploded outward, with the oxygen briefly catching fire and burning his hand and arm where he had been holding the valve. Employee #1 was transported to UCSD Medical Center where he underwent treatment for third-degree burns to his right hand and arm.