Fire extinguishing agents have to delete the task burning materials with consideration of its Brandklasse and prevailing surrounding field conditions (for example endangerment to persons or room size). They are inserted for the fire fighting by the fire-brigades or into automatic fire-extinguishing systems or are available to the self-help in portable fire extinguishers or mobile fire-extinguishing devices.

Each fire extinguishing agent possesses a main extinguishing effect and possibly a The wrong selection of the fire extinguishing agent can have fatal consequences. For example some chemical materials react with water (possible consequence: Danger of explosion) and the molecules of some chemical fire extinguishing agents at high temperatures and go new connections are broken open (possible consequence:

Water

The fire extinguishing agent water is suitable for the Brandklasse A. the fire extinguishing agent has opposite other fire extinguishing agents of advantages: it is low-priced, not malicious, not corroding, mostly sufficiently available and well promotable.

Water may not be used with burning metals, since the enormous heat would split the water up chemically - the contained oxygen would burn the fire anfachen like an explosion and the hydrogen; perhaps it can come also by the mixture of the hydrogen with atmospheric oxygen to the formation of highly explosive detonating gas (the generally spread view that the main danger would concern the detonating gas formation, is not applicable. Separate: Hot light alloy = reducing agent fragmentation of the water molecules exotherms redox reaction light alloy + oxygen).

With chimney fires water would evaporate to 1 litre water because of the spatial relations under large pressure, very much restrained in the chimney, results in 1,700 litres water vapour, and the chimney to destroy. With fires of fats and oils with temperatures above 100 "°C it is to be noted that an oil mist develops for that like an explosion burns, since with contact the water sprays evaporated and the burning oil/fat the feared fat explosion. The electrical conductivity of water saves the danger to come with high voltage in contact and to suffer an electrical impact.

Main extinguishing effect: Cooling, Suffocate

Fire-ex. powder

Fire-ex. powder is a mixture of powdered chemicals, which prevents a burn. The prevention takes place either by means of asphyxiation (Brandklassen A+D) and/or inhibition (Brandklasse B+C). Three kinds are differentiated.

Delete foam

Delete foam is a fire extinguishing agent, which is produced by adding a Schaumbildners for the water with air supplied afterwards. Delete foam works suffocating, by putting an air-impermeable layer over the inflammable material. Depending upon the relationship of the water foam central air mixture three kinds are differentiated.

Main extinguishing effect: "Suffocating" (here: Stick effect by separation) Cooling

Compressed air foam

The compressed air foam procedure (also calls CAFS: Compressed air Foam system) differs by the kind of the supply of air needed for the foaming power. As the name says, air is supplied to the water/foam mixture as compressed air. This happens in the fire-fighting vehicle, and/or with stationary resting against a pump and/or a foam central mixer, the foam is promoted completely finished by the hoses to the jet pipe. With conventional procedures air would only be taken up at the foam pipe. Detailed information in the article compressed air foam.

Wetting agent

Wetting agent is an additive to the fire fighting water for the reduction of the surface tension of the water. Normally the means used as Schaumbildner is used also for this, no air is then only supplied.

To reach wetting agent added around a penetration of the fire extinguishing agent into the combustible material. Thus also deeply or hides lying glow-type combustion, as they arise for example in the humus soil in the forest or in splinter shelters, is to be reached.

In youngest time intersperses itself ever more realization that by the employment against wetting agent also fires in buildings, for which in former times pure water was used more effectively to be fought to be able. Trained jet pipe leaders presupposed, let themselves be decreased fire fighting water damage by flowing off fire fighting water, since the water penetrates better into the combustible material and does not flow off due to the surface tension mainly.

Inert gases

The extinguishing effect of argon, nitrogen and carbon dioxide (= CO2, in principle no inert gas and therefore for fires of the Brandklassen D not suitably) is reached by the displacement of the atmospheric oxygen. One speaks here of the stick effect, which occurs on falling below the specific limit value necessary for the burn. The fire in most cases already expires during an oxygen sinking on 13,8 volume. - %. In addition the existing air volume must be displaced only around approximately 1/3, which a quenching gas concentration of 34 volume. - corresponds to %. With fire materials, which for burn substantially less oxygen needs, an increase of the quenching gas concentration is necessarily, for example with Ethin, Carbon monoxide and Wasserstoff. Since the quenching gases are heavier argon and carbon dioxide than the ambient air, they implement the flow range particularly fast and thoroughly.

Carbon dioxide

Carbon dioxide (colloquially often "carbon dioxide" or falsely "carbonic acid" mentioned) is suitable for fires of the Brandklassen B and C. Due to its physical characteristics carbon dioxide is used as only quenching gas also in fire extinguishers and fire-extinguishing devices. In stationary fire-extinguishing systems carbon dioxide is stored pressure-liquefied in high pressure steel bottles or cooled with -20 "°C in large low pressure containers. Clearly larger fire extinguishing agent supplies can be reproached by the liquid storage space-saving. Since carbon dioxide is injurious to health with high concentrations, the professional associations write during excess of the limit value of more than 5 volume. - % special preventive measures forwards. It is used above all also in electrical and electronic plants, since it is not electrically leading contrary to all water-based fire extinguishing agents and most powders. With application it must be paid attention to the fact that carbon dioxide is a breath poison and on the breath center of humans and animal works.

Carbon dioxide cannot be used for the deletion of burning light alloys (alkali and alkaline earth metals), since it is decomposed to oxygen and carbon (or carbon monoxide) (the carbon dioxide is reduced from the light alloy to CO or C, sees also redox reaction).

Main extinguishing effect: Suffocate, ( Cooling - practically however hardly relevant)

Argon

Argon is a noble gas won from the ambient air, which is stored as fire extinguishing agent for stationary fire-extinguishing systems gaseously consolidated in high pressure steel bottles. The maximum operating pressure is at 300 bar. Argon is not poisonous. However an endangerment can result from combustible gases and oxygen deficiency with the structure of the necessary delete concentration, in particular in connection with a fire event. It is to 0.93 volume. - % in the atmosphere contain. Its density in relation to air amounts to 1,38:1.

Main extinguishing effect: Suffocate

Nitrogen

Nitrogen is color, smell and tasteless gas, that to 78.1 volume. - % in the atmosphere contain. Its density in relation to air amounts to 0,967:1. As fire extinguishing agent for stationary fire-extinguishing systems nitrogen is stored gaseously consolidated in high pressure steel bottles. With an ambient temperature of +15 "°C the maximum operating pressure is at present at 300 bar. Nitrogen is not poisonous, it can however in case of application an endangerment by combustible gases and oxygen deficiency develop.

Main extinguishing effect: Suffocate

Articles in category "Fire extinguishing agent"

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