Nitrogen and water extinguishers

January 2009 Fire & Safety

Every fire needs three elements: oxygen, heat, and fuel. If only one of these elements is removed, the fire cannot spread and will inevitably go out. Automated extinguishing systems are designed on the basis of this principle. Depending on the protection objective and the application in question, different agents can be used for extinguishing fires, for example water (ie, sprinkler systems), gaseous agents (chemical gas or inert gas) or a combination of water and gas (ie, water mist). Water cools primarily the materials and the ambient air, preventing the fire from spreading rapidly. The inert gaseous agents work principally by displacing the oxygen, inerting the protected area, while chemical gaseous agents absorb the fire heat leaving the fire without energy.

In the newly developed Sinorix H2O Gas extinguishing solution, the natural extinguishing agents nitrogen and water are combined for a dual effect that quickly and reliably extinguishes the fire. While the nitrogen reduces the concentration of oxygen in the protected zone, putting the fire immediately out, the water mist lowers the ambient temperature to a level below the flashpoint of the combustible material. When discharged, both extinguishing agents are carried by the same piping network and are distributed by the same nozzles to the extinguishing area. The nitrogen also serves as a propellant for the water, assuring moderate and equal distribution. Already by using small quantities of water, the water mist mixture cools down overheated equipment and surfaces, thereby providing an additional protective effect. The water mist also reduces the risk of re-ignition. Thanks to the use of fine spraying technology, exposed surfaces are coated with only a very thin layer of water – so thin that it usually poses no risk even to electronic equipment, because it evaporates within a few minutes.

Furthermore, the water mist removes toxic fumes from the air and the room can be quickly ventilated using a ventilation system or windows. The natural extinguishing agents nitrogen and water are chemically neutral and are safe for the environment and people. (The earth’s atmosphere is composed of about 78% nitrogen and about 21% oxygen. If the oxygen percentage can be reduced to less than 13% by volume, any fire will be extinguished without posing a threat to persons in the area.)

Sinorix H2O Gas is suitable for extinguishing smoldering and deep-seated fires that can arise in closed facilities, such as archives, libraries, museums, warehouses or rooms for technical equipment.

To make the system as efficient as possible, the mixture of nitrogen and water must be tailored exactly to the specific requirements and fire risks. For this, Siemens developed a computer program that precisely calculates the dimensions of the piping network, nozzles, extinguishing range, venting, retention time, etc, for a wide range of application areas. The Sinorix H2O Gas extinguishing system as well as the calculation program have been tested and approved by VdS (Verband der Sachversicherer, European certification authority). Siemens is currently the only supplier to offer a VdS-approved gas-water combined extinguishing system for room protection. The solution offers a package of services, including risk assessment, system design, installation, commissioning, and maintenance – all from one source.

For more information contact Keshin Govender, Siemens Building Technologies, +27 (0)11 652 2412,

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