In some industries, particularly the petroleum or oil/ gas industry, reactor vessels are intentionally flooded with an inert gas such as Nitrogen, to ensure the vapour space is too low to support combustion.
Nitrogen is not itself a toxic gas, but it displaces the Oxygen. So, a purged gas environment, although it eliminates the chance of fire or explosion, produces a very real threat to human life.
Specialist breathing protection, communications, training, and working and rescue procedures are all part of safe working in inert vessels - we are however covering only the issue of gas detection.
