Abstract: On January 2, 1996, Employee #1 was assisting with the replacement of an air cylinder that controls the vertical movement of feed rolls for a Nicholson debarker machine. The electrical disconnects for the debarker were locked out, but the air system controls were not, although they were turned to the OFF position. The old cylinder had been removed and Employee #1 was attempting to attach the air line to the new cylinder. A coworker who had helped to install the new cylinder was trying to help Employee #1 by cutting off the air supply. The coworker moved to where the air controls were located and proceeded to turn on the air control valve. He turned the wrong valve, allowing the feed rolls to close. Employee #1 had positioned himself between the feed rolls and was crushed to death when they came together. An autopsy was performed.