Abstract: At approximately 9:45 a.m. on August 9, 1989, Employee #1 and a coworker were installing a 2 1/2 in. diameter by 8 1/2 ft long metal fence post in the ground. One end was inserted into the 3 5/8 in. diameter by 10 in. long sleeve of a 57 1/2 lb portable air-powered Rhino Matel PD-50 post driver. The air pressure used was 120 psi. The two employees raised the post to a vertical position with the post driver on top. Employee #1 then held the post with one hand to keep it stable, and with his other hand installed the throttle valve in the air supply hose to activate the post driver. The post driver lifted up off the pole and fell, striking Employee #1 on the head. He received multiple cuts and lacerations, for which he was hospitalized. The manufacturer's operating instructions, which employees are required to read before using the equipment, include the following cautions: operators must run at 90 psi; clear the post in the sleeve or chuck 1/8 in. to 1/2 in.; and wear a hard hat, safety glasses, and shoe protection. Neither employee was wearing a hard hat at the time of the accident. The manufacturer's instructions were not read, nor were they available. Neither employee was wearing a hard hat at the time of the accident. The pole clearance was 1 1/8 in.