Abstract: At 3:45 p.m. on September 23, 2002, Employees #1 through #4, all contract workers, were preparing the Number 3 Gasoline Perco Treater for catalysis removal, a normal maintenance task. They had closed and placed slip blinds on the inlet valve, outlet valve, and the PSV block valve. They opened the atmosphere top hatch and the 2-in. bottom atmosphere valve. After completing preparations, the employees hooked the hot water truck hose to the 2-in. atmosphere valve. They had been pumping hot water into the vessel for approximately two hours and estimated that the vessel was about one-third full when flammable vapors released from the top hatch ignited. A flash fire erupted, burning the employees. Employee #1 later died as a result of his injuries. Employees #2 through #4 were hospitalized.