Abstract: Employee #1 was using an air hammer to chip residues out of furnace #3 at an aluminum foundry. He was wearing a Bullard (#88 series) air line respirator. Two compressed gas lines with universal access couplings were attached to post #l-5. The one on the right was labeled "natural gas." The one on the left had an old paper tag attached, with the word "air" handwritten on it; however, this line actually contained pure nitrogen. A splitter diverted one part of the gas stream to the air hammer, and the other part of the stream to the air line respirator. Employee #1 was asphyxiated and killed when exposed to pure nitrogen.