Abstract: On January 13, 2003, a maintenance supervisor was standing inside of a building at a roll-up door opening. The door was fully open, with the opening measuring approximately 13-feet wide by 10-feet high. The door opening and leading edge of the floor was approximately nine feet above the concrete surface located outside the building. Two lengths of 0.375-inch chain spanning the 13 feet of opening provided barrier protection in use at the roll-up door opening. The chains in use were used to prevent falls from the leading edge of the floor surface (inside the building) to the concrete surface below. On the north end of the door, the chain ends were welded to the metal doorframe. On the south end of the door, chain hooks that were welded to the doorframe connected the chain ends. The top chain span ends were attached at approximately 44 inches above the floor surface. Chain sag of the top chain at the mid-point of the span resulted in a distance of approximately 35 inches from the chain to the floor surface. The maintenance supervisor was resting his forearms on the top span of chain, and speaking to another employee standing outside the building on the concrete surface below. The chain ends slipped out of the hooks and the maintenance supervisor fell head first onto the concrete surface below. The maintenance supervisor was killed, dying from massive head injuries.