True or False? The methods for using Class B foam on Class B fires differ from those used for Class A foam on Class A fires.

Answer: A — True

Foam suppression is tailored to the fuel and the goal of extinguishment. For solid fuels (Class A), foam works mainly by cooling and insulating the fuel, soaking into porous materials, and creating a long-lasting blanket that slows heat transfer and helps prevent reignition. The emphasis is on cooling the fire area and allowing the heat to be absorbed away from the flame. For liquid fuels (Class B), the priority is different: the foam must float on the liquid surface and form a stable film that keeps vapors from escaping and keeps the fuel and air from re-contacting each other. The goal is vapor suppression and creating a continuous surface blanket over the spill, not deep soaking. This leads to a different concentrate choice and a different application technique—often a broader, more uniform blanket and sometimes higher application rate to ensure complete surface coverage. Because the aims and the physics are different, the methods for using Class B foam on a Class B fire do not simply mirror those used for Class A foam on a Class A fire. That’s why the statement is true.