Fire prevention

Combustion of most materials does not occur at oxygen concentration lower than approx. 15 % Vol. in normal air pressure.

Atmospheric air contains about 21% oxygen and 78% nitrogen. If any inert gas is added, for instance carbon dioxide, argon or nitrogen, the standard air composition changes and the oxygen content in this artificial gas mixture is reduced. When the oxygen content is reduced at some point the fire extinguishes. But how does it affect the ability to breathe? In fact, human breathing needs a minimum of about 12% oxygen. So to suppress the fire and combustion while sustaining human life it is enough to minimise the oxygen content from 21% to less than 15%, yet not below 12%. Practically, the content of about 13.5% oxygen volume is the target level in fire suppression systems based on oxygen reduction.

Nitrogen generation systems can generate the required mixture of85-88% nitrogen volume with 12 to 15% oxygen volume in the affected zone.

Some applications require a controlled supply of nitrogen to spaces with significant leakage, such as large warehouses. Depending on specific applications, it may be advisable to inject an increased nitrogen gas content and balance the mixture by means of atmosphere control systems installed at various points.

Typically, nitrogen with a residual oxygen content of 5-16%is used for this type of applications.