Can Class A foam be used on Class B fires?

Class A foam is specifically designed for use on Class A fires, which include ordinary combustibles like wood, paper, and some plastics. It works by creating a blanket over the burning material, cooling it and preventing re-ignition.

Class B fires, on the other hand, involve flammable liquids such as gasoline, oil, and other hydrocarbons. For these types of fires, foam agents specifically formulated for Class B fires are necessary. Class B foam contains additives that are designed to suppress flammable vapors and penetrate the liquid fuel layer, which Class A foam does not effectively do.

While there may be some situations where Class A foam could have a minor effect on Class B fires, particularly in emergencies where no other options are available, it is not recommended as a suitable primary agent for these types of fires. Therefore, the use of Class A foam on Class B fires is generally not effective or appropriate, making the answer to the question improper.