Class B Foam is designed for use on which fires?

• A. Unignited or ignited Class B flammable or combustible liquids.
• B. Wood and paper fires.
• C. Electrical equipment fires only.
• D. Water-soluble solvents.

Answer: (A)

Foam concentrates classified as Class B are used to fight fires involving flammable or combustible liquids. They work by forming a stable film on the liquid surface and cooling the fuel, which blankets the fire, reduces vapor release, and helps prevent reignition. This makes them effective for both unignited and ignited liquid fires, such as gasoline or solvents, where the fuel is the primary hazard.

They aren’t suited for solid fuel fires like wood or paper (that’s Class A), and they’re not the primary choice for electrical equipment fires (Class C) where energy conduction and safety are concerns. Some solvents can be involved in Class B scenarios, but the main purpose of Class B foam is to suppress fires of flammable liquids, so the best fit is fires involving unignited or ignited flammable or combustible liquids.