In chemical terms the combustion process is a fast running reaction between a flammable material and atmospheric oxygen induced by the ignition temperature. To extinguish a fire the burning material must be separated from the atmospheric oxygen or cooled down to below the combustion temperature. This is exactly what fire extinguishing foam does.

The following fire extinguishing effects are utilised when using fire extinguishing foam:
 

Separating effect
The closed foam cover separates the combustion zone from the ambient air and prevents any further supply of oxygen to the flammable material.

Cooling effect
The water drained from the foam evaporates in the area of the flame front whereby heat is withdrawn and the re action velocity between the flammable material and atmospheric oxygen is reduced significantly. The flammable material is cooled down by the water/ foam solution discharged by the foam.

Cover effect
The closed foam cover stops any further gas evaporation from burning materials, i.e. flammable gases from the incendiary matter can no longer get into the combustion zone Cooling the burning material at the same time reduces the vapour pressure whereby outbursts of gas and thus re-ignition are avoided.
The preventive application of foam onto spilled volatile products prevents emissions harmful to the environment This also significantly reduces the danger of fire.

Suppression effect
Flooding spaces channels, plant parts, etc with high or medium expansion foam suppresses the flammable vapours/gases from the atmospheric oxygen necessary for the combustion process.

Insulation effect
The low thermal conductivity of the foam insulates flammable material which has not yet caught fire or has already been extinguished against thermal radiation and ignition sources.
 

Film formation
a) Aqueous film (AFFF effect)
The foam produces a very thin aqueous film an non polar liquids This film floats ahead of the foam and provides for its excellent flowing, extinguishing and re-ignition inhibiting properties The aqueous film also forms when using non aspirated foam concentrate solutions, e. g. in sprinkler systems, water monitors, spray nozzles etc.

b) Polymer film
The polymer film is produced by the polymer film formers contained in the foam when extinguishing polar hydrocarbons (e.g alcohols, ketones, ester) The film floats as an insulating protective layer between the foam destroying alcohol and the foam cover above Only when the foam is applied gently a stable continuous polymer film is formed which provides effective protection against the foam destroying liquid