Firefighting foam

Firefighters sprayed foam on structures in the Mammoth Hot Springs complex on 10 September 1988 during the Yellowstone Fires.

Firefighting foam is a foam used for fire suppression. Its role is to cool the fire and to coat the fuel, preventing its contact with oxygen, resulting in suppression of the combustion. Fire-fighting foam was invented by the Russian engineer and chemist Aleksandr Loran in 1902.[1]

The surfactants used must produce foam in concentration of less than 1%. Other components of fire-retardant foams are organic solvents (e.g., trimethyl-trimethylene glycol and hexylene glycol), foam stabilizers (e.g., lauryl alcohol), and corrosion inhibitors.


  • Low-expansion foams such as AFFF, have an expansion rate less than 20 times are low-viscosity, mobile, and can quickly cover large areas.
  • Medium-expansion foams have an expansion ratio of 20–100.
  • High-expansion foams have an expansion ratio over 200–1000 and are suitable for enclosed spaces such as hangars, where quick filling is needed.
  • Alcohol-resistant foams contain a polymer that forms a protective layer between the burning surface and the foam, preventing foam breakdown by alcohols in the burning fuel. Alcohol-resistant foams are used in fighting fires of fuels containing oxygenates, e.g. MTBE, or fires of liquids based on or containing polar solvents.
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