Department of Defense (DoD) ARFF CDC Practice Exam 2025 – 400 Free Practice Questions to Pass the Exam

In the context of extinguishing fuel spills and suppressing flammable vapors, low expansion foam is particularly effective due to its density and the capability it has to create a barrier between the fuel and the air, thereby smothering the flames and preventing re-ignition by suppressing vapor release. This type of foam expands at a lower ratio compared to other types, allowing it to form a thicker blanket over the surface of the fuel, effectively smothering the fire.

While high expansion foam is used in specific scenarios, such as enclosed spaces or where rapid filling of area is necessary, it is not typically the first choice for fuel spills which require a more stable coverage. Aqueous film-forming foam (AFFF) is indeed a powerful contender for fuel fires due to its ability to quickly spread and form a film on the surface of flammable liquids, but it is classified under low expansion foam. Alcohol-resistant foam is designed for fires involving polar solvents, providing a protective layer, but is not primarily used for the general class of hydrocarbon fires unless specifically required. Therefore, low expansion foam remains a standard choice for general fuel spill incidents.