Confined Spaces are inherently hazardous places of work and exist in many industries.
In some industries, particularly the petroleum or oil/ gas industry, these are intentionally flooded with an inert gas to ensure the vapour space is too low to support combustion. Nitrogen is typically used, and this works well for controlling fire or explosion in the vessel, but produces a potential inhalation hazard.
Whilst Nitrogen in itself is not a hazardous gas (approximately 78% of the air we breathe is composed of Nitrogen), when used in processing for reducing fire/ explosion risk, it is in pretty much 100% concentration and leaves no room for Oxygen, the essential gas for supporting human life. Nitrogen is slightly lighter than air and will mix freely with air.
A vessel purged with Nitrogen will cause asphyxiation within seconds if it is entered without adequate protection, or if the exhaust gas from the vessel is inhaled.
Immediate human reactions to purge gas
The immediate reaction is marked by struggling for breath, and unconsciousness follows in a few seconds if the worker is not removed. There has been numerous cases where persons are exposed to exhausting inert gas and losing consciousness immediately from here there are 2 options:
- The worker falls away from the inert gas into air which is safe, in which case typically the worker comes round within seconds.
- The worker falls into the inert gas which results in fatality.
