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Managing Safety in Nitrogen Inerting Fire Sprinkler Systems


Managing Safety in Nitrogen Inerting Fire Sprinkler Systems (195 kb)

The most effective method for removing oxygen from an enclosed space with nitrogen is using a “fill and purge” breathing process. This process consists of repeatedly filling and venting the closed vessel, in this case fire sprinkler system piping, with high purity nitrogen gas. Each high purity nitrogen fill step dilutes the gas mixture already present in the piping, lowering the resulting concentration of oxygen in the gas mixture. With repeated ‘fill and purge’ cycles, the oxygen concentration will eventually be reduced to extinction.

The primary danger of using nitrogen gas, regardless of its source, is the inherent risk of asphyxiation, i.e. limiting the availability of oxygen for human respiration. By definition, high purity nitrogen gas contains little to no oxygen, the gas required to support human life. Not only does exposure to an oxygen deficient environment reduce the amount of oxygen inhaled with each breath, inhalation of high purity nitrogen can act to draw dissolved oxygen out of the blood stream, vary rapidly reducing the blood oxygen content to dangerous levels.

Because there is no possibility for the instantaneous release of a large quantity of nitrogen gas, nitrogen generators that employ membranes for separation of nitrogen gas from the compressed air feed are the safest nitrogen gas source for performing Wet Pipe Nitrogen Inerting (WPNI) and Dry Pipe Nitrogen Inerting (DPNI).”