Abstract: On January 25, 1990, Employee #1 was working beneath a pipe rack in the "lean oil" unit at a natural gas processing plant. He was apparently tracing the lines looking for any apparent problem before starting up the unit. He had been in the pipe rack earlier in the day to partially open a steam valve and had asked a coworker to finish opening the valve for him. Employee #1 was a heavyset man weighing approximately 250 lb, according to information gathered during investigation. He had recent knee problems. At approximately 1:30 p.m., according to interviews, Employee #1 apparently fell from room level to the flat concrete walk beneath the pipe rack. He suffered two ruptured discs in his back, bruises, and a cut to the back of his head. No one saw the accident and no one could confirm whether or not he had been in the pipe rack (12 ft 5 in. above the walkway) or whether he had fallen from the overhead pipe rack. At the accident scene and during his hospital stay, Employee #1 said that he had not been in pipe rack prior to the fall. On February 10, 1990, Employee #1 died of a blood clot that probably developed as a result of his injuries.