Which substance is used as a foaming agent in fire extinguisher?

This question tests knowledge of foam fire extinguishers. The correct answer is Aqueous Film Forming Foam (AFFF), which is widely used in foam extinguishers to suppress fires involving flammable liquids.

AFFF forms a thin film over the surface of burning fuel, cutting off the oxygen supply, cooling the fire, and preventing the release of flammable vapours. It is especially effective against Class B fires, such as those involving petrol, diesel, and other flammable liquids.

• Nitrous Oxide: Used as an anaesthetic and oxidizer, not in fire extinguishers.
• Methane: A flammable gas and not a firefighting agent.
• AFFF: The standard foaming agent used in foam fire extinguishers.
• Carbon Monoxide: A poisonous gas with no use as a fire-extinguishing foam.

Therefore, the correct answer is: Aqueous Film Forming Foam (AFFF).