In the event of applications on polar solvents, which are water soluble, the use of alcohol resistant AR-AFFF filming foam is necessary. Once applied on polar solvents, the polymers (polysaccharides) contained in the foam form a polymeric film over the surface of the liquid. The polymeric film is generated by a reaction between the polar solvent and the water that is drained from the foam. The aqueous film that floats over the polymeric layer maintains its ability to autogenerate itself and contributes to extinguishing the fire and suppressing any vapours.
Main use: wet sprinkler or deluge systems used to protect inflammable liquids.
AFFF and AR-AFFF foams can be mixed with water in the percentage of 3% and 6% and are approved by the Home Office.
Water/medium and high expansion foam systems
High expansion foam is used to extinguish class A and B fires inside confined spaces. Medium expansion foam was instead studied for applications in open air and windy spaces.
Both medium and high density foam are bubble aggregates generated mechanically thanks to the passing of the concentrated foaming agent through special generators and the subsequent contact with air. The expansion of the foaming agent can vary between 20:1 and 1000:1.
Medium expansion systems can be used to protect liquid and solid combustibles where an extensive coverage of the spaces to protect is required, such as for the total flooding of small volumes such as cabins with engines and transformers. They are used to protect inflammable or toxic liquids where the rapid saturation is vital to prevent the propagation of vapours both for indoor and outdoor applications.
High expansion foams are also used to protect inflammable liquids and guarantee an even more extensive coverage of the spaces to protect. They are recommended mostly for the protection against different types of risks on various levels, such as inside palletised warehouses, for example.