Abstract: At approximately 1:00 p.m. on October 27, 1999, two instrument technicians were replacing a thermal coupling inside a cold box. One employee went to the control room and requested an oxygen monitor, and was told there was one in the safety room. He unplugged the monitor and walked out the door with it. He turned it on and believed it was an automatic monitor because it was reading 20.9 percent oxygen. However, he failed to turn on the pump of the monitor. He got to the cold box and inserted the probe into the space and obtained a reading of 20.3 percent oxygen. He moved the probe to a different location and continued to read 20.3 percent oxygen in the space. With both readings, he failed to turn the pump and the readings were, therefore, inaccurate. Employee #1 descended into the cold box using a portable step ladder. The other employee then went to ensure the nitrogen purge valve was turned off. When he came back, he saw Employee #1 on the ladder with his head stuck inside the cold box, slumped over with his hands to the side and his body was shaking and quivering. Other employees helped to pull Employee #1 from the cold box. He was flown to Herman Hospital and pronounced dead due to asphyxiation.