Abstract: Employees #1 and #2 and five coworkers were preparing part of a crude unit for turnaround. The system was being washed with water to flush all hydrocarbons into the fractionation tower, where the mixture of water and hydrocarbons was being drained onto the floor and hosed into a nearby open sewer. A series of operating heaters was located 35 to 50 ft downwind. A slug of light hydrocarbons was washed from the tower onto the apron. Employee #1 smelled the hydrocarbons and went to the drain valve and closed it. Before he could walk away, the vapors were ignited by the heater and he was engulfed by a fireball and killed. Employee #2 was overcome by heat and smoke while she was fighting the fire. None of the employees recognized the hazardous nature of the situation.