Abstract: At about 9:30 AM on March 3, 1997, Employee #1 and a coworker began inspecting a heat-treating vessel, which measured 2.7 meters deep and 1.5 meters in diameter, in preparation for repairing a leaking valve. Employee #1 wanted to examine the pipe that led from the valve to the vessel. The coworker told Employee #1 that the space should not be entered without proper personal protective equipment and paperwork. Employee #1 said that he was not going to be in the space long and he was not going to do the paperwork for such a short job. While the coworker was removing the lid of the vessel with a 4.5-metric-ton hoist, Employee #1 placed a ladder into the vessel and entered it. When the coworker turned around, he saw Employee #1 trying to climb up the ladder and then falling to the bottom of the vessel. The coworker called the First Response team, which removed Employee #1 within 4 minutes using the 4.5-metric-ton hoist. They began cardiopulmonary resuscitation and continued until relieved by the ambulance crew. Employee #1 was then taken to a hospital, where he was pronounced dead of argon asphyxiation at 10:41 AM. The atmosphere in the space was tested and found to contain 5.2 percent oxygen.