Diluent extinguishants.

The termination of burning by means of dilution consists in the decline of oxidizing agent concentration (oxygen of air) up to 15% of a volume and less under which burning is stopped.

The method of termination of burning by means of dilution is used at fire extinguishing in the confined space, for example, such as: power plants, baggage compartments and passenger cabins of aircraft, drying chambers, production areas.

This method is used at extinguishing of active fires at the overflow of aviation fuel on considerable areas or substance burning in the reservoir of small diameter.

The extinguishants are supplied at such method of extinguishing either in air, that enters burning zone, or in the combustible substances. These are sawed water, volatile acid, water vapour, nitrogen and other rare gases.

Volatile acid CO₂ is the main diluent extinguishant that presents by itself the real gas without a color and smell, heavier than air in 1.5 times. 1 kg of liquid carbon dioxide yields near 509 L. of volatile acid.

High toxicity is the basic disadvantage of volatile acid, and already 20% bulk concentration of carbon dioxide in the air space of apartment is fatal for a human being at breathing during a few seconds. At using of carbon dioxide as space extinguishing mean the personnel of fire-and-wrecking units being present in the apartment under burning, must use respiratory protective devices.

Carbon dioxide can not be used for extinguishing the fires of magnesium and titanium alloys through high temperature of burning zone (over 3000 ^oC), because of at temperatures equal or more 3000 ^oC, carbon dioxide resolves into a carbon and oxygen. In addition, 1 kg of carbon dioxide yields near 730 gr. of atomic oxygen that enters in burning zone & reacts with a metal and strengthens its burning.

Carbon-dioxide equipment as movable fire extinguishers ОУ-2, ОУ-80 and ОУ-400 is used at parking area in the open air. It is necessary to take into account at their using, that temperature -25 ^oC is critical, and at the temperatures of ambient air -60 ^oC and below all the carbon dioxide in fire extinguishers goes into the liquid state and freezes.

Water vapour as extinguishant is used for extinguishing the fires on surface facilities of civil aviation in leaktight compartments with a volume up to 500 m³, equipped with stationary fire-fighting system (drying chambers, pumping plants of POL service).