Abstract: On October 24, 1994, Employee #1, an industrial hygiene technician for Arco, where he has worked for 13 years, was assigned to oversee contractors who were gathering bulk samples of refractory from DeFlores heater #2 in the 51 vac unit. The contractors were trying to determine if asbestos was present in the heater unit, which had been taken out of service and was to be demolished. Employee #1 was the third person to enter the unit. Two contractors had already entered the heater unit and were standing on a 5 ft wide circular ledge. Toward the center of the heater or ledge was a 17 ft, 2 1/4 in. drop. When Employee #1 entered, he took one step to the left and immediately fell. He suffered a contusion to the head and a fractured right tibia and L1 vertebra. Employee #1 was wearing a respirator with a HEPA filter, a Tyvek suit, safety glasses, and a hard hat. The other contractors were wearing the same ppe except that they also were wearing fall protection. The accident's causal factors were that Employee #1 was unaware of the hazards and that he was not wearing the fall protection needed to safely enter and exit the unit.