Foam fire extinguishers with additive, have the effect of improving a water based extinguisher, enabling it to fight Class A and Class B fires.
Advantages: Foam provides a lasting blanket to control the fire after the extinguisher discharge is complete. It can be used as a vapour-suppression barrier over flammable liquid spills.

Disadvantages: The extinguisher is an aqueous solution which requires to be cleaned up after use, particularly on painted surfaces, and must not be used on fires involving energized electrical equipment.