Abstract: Three employees were welding on large curtain box assembly for top of electric arc furnace. The 44-in. by 20ft doors were opened to allow a crane to make a pick from furnace area below. While waiting for crane, the welding crew leaned out over a waist high rim of the end door to watch a crew working in the furnace below. While employees #1 and two co-workers were observing the operation, the door on the west side had been opened mechanically by solenoid action and held in place by the air pressure on the cylinder. Over approximately 20 to 30 minutes later the available air to the cylinder leaked off and the door subsequently slammed shut, crushing Employee #1 between the ledge (rim of door area) and bottom of door killing him.