Aqueous Film Forming Foam (AFFF) is a synthetic firefighting foam, primarily used to extinguish flammable liquid fires, particularly those involving fuels like gasoline. It achieves this by creating a thin, spreading film on the fuel's surface, which helps to suppress vapors and prevent re-ignition. AFFF contains fluorosurfactants, which contribute to this film-forming capability and rapid spreading. However, it's important to note that AFFF contains PFAS (per- and polyfluoroalkyl substances), which have raised environmental and health concerns.