When it comes to choosing a fire extinguisher you need to assess the type of fire risks present and compare these risks with the fire suppressant properties of the different types of fire extinguisher available. Foam fire extinguishers are increasingly popular and are now available in a wide range of sizes to suit a variety of applications.
When applied to a fire, an Aqueous Film Forming Foam fire extinguisher- to give them their full name- forms a film of non-combustible chemical between the combustible material and the oxygen in the air. Without oxygen the fire cannot burn and is extinguished. The Foaming agent is normally suspended in water making them effective on Class A combustible solids like wood, paper and fabrics, however they have a major advantage over water only extinguishers in their ability to extinguish Class B flammable liquid fires, typically petrol, diesel, paints and solvents. Unlike water the foam “floats” on top of these fuels maintaining the oxygen barrier and smothering the fire under the blanket of foam.
This versatility makes a foam fire extinguisher a good choice for garages and petrol station forecourts and in industrial premises that store of use flammable hydrocarbon fuels and chemicals. There are chemical variations within the broad description of Foam extinguishers to tackle specific fire risks, notably the ABF foams that offer an alternative to a Wet Chemical fire extinguisher for cooking oil and fat fires. Foam extinguishers have the added advantages that they do not leave a heavy residue like say the dry powder alternatives and the extinguishers themselves are also lighter to handle than water equivalents.
If your fire risk is predominantly solid combustibles such as paper files and flammable liquids are a minor factor in your operation you it is probably better and more economical to opt for a water fire extinguisher or water additive extinguisher backed up by a small 2kg dry powder. If you store flammable liquids or use them routinely in your work then foam is the answer as you have the added safeguard of its Class A rating.