Extinguish fire

Extinguish fire

Extinguish fire

There are several methods of putting out a fire that address what a fire needs to exist: fuel, heat and oxygen So if you want to stop the flames, you have to turn off at least one of these elements.

Withdraw fuel
A fire needs a constant supply of flammable substances. If it is possible to remove all fuel from its vicinity, it must soon be extinguished. This applies both on a small scale and on a large scale. As a preventive measure against forest fires but also for active fire fighting, firebreaks are created. These clearing strips in a forest should be so wide that a fire cannot “jump over” them.

Fire brigade extinguishing Paul-Georg Meister pixelio.de
Fire brigade when extinguishing Paul-Georg Meister Pixelio.de

Decrease heat
A fire itself generates heat, which in a chain reaction enables further combustion. On the other hand if the temperature falls below the fire point or flash point the fire goes out. People take advantage of this effect in the most common method of fighting a fire extinguishing with water Contrary to popular belief, it is not the moisture that fights the fire, but the cooling provided by the water The fire heats the water until it turns into water vapor and loses energy in the process. Theoretically, fire can also be cooled in other ways, but water usually has the advantage of being available in large quantities.

Attempting to extinguish the fire with snow would hardly bring any advantages compared to water, since, for example, an apartment fire can reach temperatures of over 1000 degrees, whereas the temperature difference between liquid and frozen water is marginal.

Cut off the supply of oxygen
Fire is usually based on an oxidation process with oxygen. If you want to start a fire like a grill or a fireplace you have to improve the oxygen supply. In order to extinguish a fire, the opposite is necessary: ​​The extinguishing agent used in this case should create a separating layer between the fire and the outside air. The separating layer prevents the oxidation from continuing. The fire is, as they say, “suffocated”.

Sand, foam, fire blankets or extinguishing powder can be used as separating materials Some fire extinguishers are filled with foam or so-called ABC powder. The extinguishing powder consists mainly of the flame-retardant substances ammonium dihydrogen phosphate and ammonium sulfate.

In addition to the primary cooling effect, extinguishing water also helps to reduce the supply of oxygen. The water heats up to form water vapor, which can cover the seat of the fire like a shielding cloud.

Fire classes
Not every fire can be fought with the same methods and extinguishing agents. For example, fat fires must never be extinguished with water The water droplets are enveloped in the hot fat, expand quickly, become gaseous and create a dangerous explosion in the process.

The European Union has defined five “fire classes” for a successful and safe extinguishing process. All flammable substances can be classified in this standard:

Fire class A Solid fires, e.g. of wood or coal, which can be extinguished with water, among other things
Fire class B Liquid fires, e.g. from gasoline or alcohol, which can be smothered with foam, powder or carbon dioxide
Fire class C Gas fires, e.g. of natural gas, hydrogen or methane, which are primarily fought with extinguishing powder after the gas supply has been stopped
Fire class D Metal fires, a comparatively rare type that can best be smothered with so-called D extinguishing powder as a makeshift with completely dry sand or cement powder
Fire class F fat and oil fires which, like metal fires, should never be treated with water; In addition to professional fire brigade extinguishing agents, the best chance is to smother a grease fire in a pan with a lid.