Main types of fire extinguishers.

Main types of fire extinguishers.

Main types of fire extinguishers

A fire extinguisher is a portable or mobile device for extinguishing fires by releasing a stored extinguishing agent. When a fire extinguisher is activated, a substance capable of extinguishing the fire begins to emerge from its nozzle under high pressure. Types of fire extinguishers depend on the substance they contain. Such a substance can be foam, water, a chemical compound in powder form, as well as carbon dioxide, nitrogen and other chemically inert gases.

Types of fire extinguishers by substance

Let's consider the characteristics and properties of the main types of fire extinguishers according to their operating principle and the substance they contain: gas (carbon dioxide, freon, bromine freon), foam (chemical, chemical air-foam, air-foam), powder and water.

• Gas fire extinguishers

  Let's consider gas fire extinguishersusing carbon dioxide as an example. Liquefied carbon dioxide (carbon dioxide) is used as an extinguishing agent in such fire extinguishers, as well as aerosol and carbon dioxide-bromoethyl, in which halogenated hydrocarbons are used as a charge, when supplied to the combustion zone, extinguishing occurs at a relatively high oxygen concentration (12-18%). Gas fire extinguisherscarbon dioxide can be either manual or mobile. Manual fire extinguishers are identical in design and consist of a high-strength steel cylinder, into the neck of which a valve or pistol-type shut-off and starting device is screwed, a siphon tube, which serves to supply carbon dioxide from the cylinder to the shut-off and starting device, and a snow-forming bell. Use gas fire extinguisherscarbon dioxide type, by directing the snow-making funnel towards the fire source and turning the flywheel all the way or pressing the lever of the shut-off and starting device. When carbon dioxide passes from a liquid to a gaseous state, its volume increases by 400-500 times, accompanied by a sharp cooling to a temperature of -72 °C and partial crystallization; to avoid frostbite of the hands, do not touch the metal funnel.

• Foam fire extinguishers

  For extinguishing fires using fire extinguishing foams — chemical or air-mechanical — foam fire extinguishers are intended. Chemical foam is obtained from aqueous solutions of acids and alkalis, air-mechanical foam is formed from aqueous solutions and foaming agents by flows of working gas: air, nitrogen or carbon dioxide. Chemical foam consists of 80% carbon dioxide, 19.7% water and 0.3% foaming agent, air-mechanical foam consists of approximately 90% air, 9.8% water and 0.2% foaming agent. Foam fire extinguishers are used to extinguish with foam incipient fires of almost all solids, as well as flammable and some flammable liquids on an area of ​​no more than 1 m2. Foam fire extinguisherscannot be used to extinguish electrical installations and electrical networks that are under voltage. They cannot be used to extinguish alkali metals sodium and potassium, because they, interacting with water in the foam, release hydrogen, which intensifies combustion, as well as when extinguishing alcohols, since they absorb water, dissolving in it, and when they come into contact with them, the foam quickly collapses. Foam fire extinguishers use sodium azide as a gas-forming reagent, which easily decomposes with the release of a large amount of nitrogen.

• Powder fire extinguisher

  Powder fire extinguisher ophas two types — general-purpose powder fire extinguishers that can extinguish fires of classes A, B, C, E; general-purpose powder fire extinguisher for extinguishing fires of classes B, C, E. The op powder fire extinguisher is the most universal in terms of its area of ​​application and operating temperature range (especially with an ABCE charge), which can successfully extinguish almost all classes of fires, including electrical equipment under voltage of up to 1000 V. The op powder fire extinguisher is not intended for extinguishing fires of alkaline and alkaline earth metals and other materials that can burn without access to air. It is prohibited to extinguish electrical equipment under voltage higher than 1000 V with powder fire extinguishers. When extinguishing a fire with powder fire extinguishers, it is necessary to take additional measures to cool the heated elements of the equipment or building structures.

• Water fire extinguishers To extinguish class A fires, water fire extinguishers should be used. It is prohibited to use water fire extinguishers to extinguish fires in equipment under electrical voltage, to extinguish highly heated or molten substances, as well as substances that enter into a chemical reaction with water, which is accompanied by intense heat release and splashing of fuel.