Abstract: On May 20, 2004, Employee #1, a welder, and a coworker-helper were working for a mechanical contractor at a refinery. At 7:00 a.m., a hot work permit, Number 420446, had been issued for hot work on the Number #1 Lift Station Oil Trap-Whole Bay. At approximately 11:00 a.m., another of the contractor's work crews removed an air blower from an overflow pit adjacent to the oil trap and placed metal covers over the top of the overflow pit. The air blower had been used to keep hydrocarbon vapors from backing up into the overflow box. About two hours later, this same work crew anchored a come-along to a valve box and used it to move one of the metal covers into place. This valve box was bolted to the metal plate sitting on the northern half of the overflow pit. Anchoring the come-along to the valve box caused the plate holding the valve box to flex, breaking the vapor seal along the north side of the plate. Despite these two changes in the conditions adjacent to the southeast corner of the lift station oil trap, the hot work permit was not terminated. At approximately 3:46 p.m., a coworker was using a cutting torch to cut a diamond plate adjacent to the northwest corner of the overflow pit. Employee #1 was setting up to weld north of the coworker-helper. The torch operator was east of the coworker-helper and was attempting to fight a fire when he noticed material burning next to the cutting operation. At that time, the hydrocarbon vapors ignited and a flash of flames shot out from under the plate covering the north side of the overflow pit. Employee #1 sustained second-drgree burns to the left side of his face, for which he was hospitalized for five days. The coworker-helper suffered second-degree burns to small areas on his left hand and on the back of his left leg. He was trabsposted to the hospital, where he was treated and released. It was later determined that the coworker-helper's coveralls looked like they were made of fire retardant material, but were not.