Abstract: At approximately 10:00 a.m. on April 10, 1996, Employee #1 was on the floor of the #4 Cooper 550 drilling rig. He and coworkers had pulled all the drill steel out of a natural gas exploratory well to change drill bits, and were preparing to begin running the drill pipe back into the hole. Employee #1 was getting ready to throw the spinning chain on the first section of pipe when he noticed the chain had bled out of the air winch and was hanging straight down below the floor. The winch would slowly bleed out the chain because the valve did not shut off properly. Employee #1 reached into the winch extension bar next to the winch to suck up the slack. He did not notice that the chain end was tied off. When the slack was pulled up, Employee #1's arm became caught in the chain loop and was pinched between the chain and the angle iron of the winch roller. He suffered torn muscles, ruptured veins, and a torn artery in his left arm just above the elbow that required surgery.