Abstract: Employees #1 and #2 were part of a crew installing an oxygen feed mixer on the fifth floor of the etox unit. An enclosure had been made by wrapping the opening of a large pipe with black plastic, and Employees #1 and #2 entered this enclosure to check with a black light the surface of the pipe's flange for oil contamination. The pipe was filled with nitrogen, which was being put into the process equipment to prevent rusting. Employees #1 and #2 were overcome in the oxygen-deficient atmosphere. Coworkers in the immediate area could not see through the black plastic that the men were in trouble, and so did not respond in a timely manner. Finally, a contractor determined that there was a problem and the plant's emergency response team arrived and provided emergency medical treatment. Employees #1 and #2 were transported to the hospital, where Employee #1 was pronounced dead. Employee #2 was still recovering from the incident and appeared to be suffering from short-term memory loss.