Compressed air foam system

Compressed air foam (abbreviation: DLS), in English Compressed Air Foam ( Abbreviation: CAF) is a special type of foam, which is used by the fire brigade.

The common abbreviation CAFS (Compressed Air Foam System ) refers to the compressed air foam generating system ( compressed air foam system, Abbreviation: DLSA ).

DLS is in contrast to conventionally foamed foam not only in the beam, but even during the mixing of the water with the foaming agent is foamed by means of compressed air. Due to the expansion of the compressed foam at the nozzle as well as the fact that no energy is consumed for the air admixture, this foam can be substantially further thrown.

Compressed air foam was originally developed in the 1930s in Germany. In Europe, CAFS was first introduced in 1997 by the professional fire brigade Ingolstadt in a pilot project and field-tested. Based on the positive results, the state of Bavaria decided the first federal state to promote the new extinguishing agents.

Advantages and disadvantages of the method with respect to water and tap water

Often DLS is praised for its supposedly excellent extinguishing properties in the class A fires. However, this is not clearly demonstrated in tests. In particular, is often criticized that DLS is tested against pure water. Tests against mains water would be much more interesting and meaningful, since a large part of the DLS own better extinguishing effect is based on the net effect of the foaming agent used. However, a DLS system is many times more expensive compared to a pure foaming agent Zumischanlage - a particularly striking disadvantage of this erasure method and therefore one of the main reasons why DLS is controversial.

In particular, the advantage of the extinguishing agent lies in the effective extinguishing effect. However, the is to oppose that particular extinguishing success and efficiency depend primarily on the virtuosity of the jet leader in fire class A fires - which have attempts by the Research Centre for Fire Protection Technology ( FFB) at the University of Karlsruhe (TH ) result. It should also be, so often made ​​and repeated statement to expect no water damage in the fire room when used properly. This is the one achieved by the over water lower flowability of the foam, to a very significant part but as well by the capabilities of the jet leader. According to the FFB provides - in addition to the security benefit of the increased casting distance and in addition to the ease of handling of the tubes due to their lower weight - the improvement of student success of the lance guide the main advantage of the DLS - erasure method dar.

The white foam over the burning material and remains there even longer there for solids in general. Since the foam evaporates immediately when the burning material is still very hot, you can consider this fact as an aid to assess whether further application of extinguishing agent is necessary. Furthermore, the foam layer cushions the evaporation and condensation of water applied from the burning material; the view is subjectively much faster better than other extinguishing agents such as water or mains water.

However, these properties are not only beneficial, but also bring significant disadvantages: When a solid combustible material of foam is covered, might get the impression that the fire was deleted even though inside any embers are still available. This danger is especially in " dry " foam, which gives the water contained rather slowly.

A peculiarity of foam in general is that it shields heat radiation. Therefore, a layer of foam on the burning material hinder the use of thermal imaging cameras. Foam on the mask visor of respiratory protective equipment makers - particularly to be expected in the internal drive - obstructs the view and can be removed only with difficulty. Furthermore, with a foam layer at the bottom of accident risk, since obstacles can be hidden under the foam.

Also, the fact that the foam is present in the compressed tube (usually 5-10 bar ), not only has advantages: When bursting a hose there is a loud bang, which is not the case with water, because of the lack of compressibility. If a hose bursts in the immediate vicinity of a people, pop trauma could be envisaged. Firefighters who were at job sites where there was such a to bursting, expressed its surprise at the cause - they had kept the loud bang, usually for a bursting gas bottle. Due to the high stored energy which is released on the bursting, the hose can - especially if the demolition is carried out on a clutch - develop a non-negligible power and even cause damage to property. Cases in which people were hit by such hoses or couplings, are fortunately not yet become known.

Problems

On 17 December 2005 crashed when using the fire Tübingen two firefighters fatal. Case of fire fighting in the attic of a half-timbered house, one floor below the fire flared up again. Due to a Schlauchplatzers the two firefighters had now no more erase means available to find their way back " freizulöschen ". Both suffocated before the emergency squad was able to find the two after 20 minutes. In the reconstruction of the accident in January 2006 turned out - for fire experts surprisingly - found that a container filled with CAFS hose may burst very quickly due to heat. The reason seems to be that the compressed air - foam mixture the hose is not as good as water cools. Apparently losing hoses therefore quickly their strength - and burst. The Interior Ministry of Baden- Württemberg responded immediately: "The rapid burst the tubing can provide our forces for fire fighting in buildings, ie the so-called inside attack, in sudden and unpredictable dangerous situations. Regardless of whether this is causally related to the fatal accidents in Tubingen, we have out of concern for the safety of our firefighters now immediately informed of this state of affairs, " state Fire Chief Hermann Schroeder said on Wednesday, 18 January 2006 in Stuttgart. " The fire service we give special recommendations on how they should proceed with the use of compressed air foam ," the country's chief fire officer on. "This is especially true when an internal drive when the pressure hoses may come into contact, for example, with glowing, burning, or otherwise heated parts. The compressed air foam method, which means an improvement in firefighting because it reduces inter alia water damage may be otherwise continue to apply with respect to this warning. A final assessment may be issued only after extensive tests. " ..

The technical committees, such as for example, the manufacturer of the hoses or the Standards Committee of the Ministry of Interior were also informed that they should consider any improvement of the equipment or the use of tactics.