By Philip Paff
In Australia, a great deal of attention is on the past use of aqueous film forming foam (AFFF) containing perfluorinated compounds (PFCs) such as perfluoro-octanoic acid (PFOA) and perfluoro-octane sulfonate (PFOS) by municipal, industrial, and defense force agencies.
The use and effectiveness of these firefighting foams produced from the 1960s to the early 2000s was good; however, the ongoing development of fuel, environmental, and personnel contamination issues saw a reduction and eventual phasing out of AFFF in the early 2000s. AFFF was intended to extinguish hydrocarbon-based flammable and combustible liquid fires (Class B). Firefighter contamination may have occurred during training or periodic vehicle maintenance. You may have seen AFFF use during foam training or demonstrations such as a simulated boat fire or aircraft crash.
These foam concentrates were mostly water and included a mixture of components such as solvents, biocides, corrosion inhibitors, and foaming agents. The added fluorinated surfactants based on PFOA and PFOS displayed the desirable properties of simultaneously being water and fat repellent. This property assisted with foam solution spread, thereby forming a thin layer over the fuel and creating a barrier that minimized evaporation and reduced heat flux from flame to the fuel, which, in turn, canceled out the feedback loop and extinguished the fire.