Which type of foam is classified as a Class B additive?

Aqueous Film-Forming Foam (AFFF) is classified as a Class B additive because it is specifically designed to combat flammable liquid fires, such as those involving hydrocarbons and polar solvents. AFFF works by forming a film on the surface of the burning liquid, which helps to suppress vapors and cool the fire, effectively preventing the fire from spreading and allowing for safer extinguishment.

This classification of AFFF as a Class B additive is essential for understanding its application in firefighting, especially in situations involving fuels and chemicals that do not respond well to water alone. The formulation of AFFF makes it particularly effective for this purpose, as it enhances the suppression capabilities against ignitable liquids.

In contrast, other options like water mist are primarily effective for cooling and extinguishing solid materials and not designed specifically for flammable liquids. Dry powders may also be used for flammable liquids but do not provide the same film-forming properties as AFFF, limiting their effectiveness in certain scenarios. Chemical foam serves a similar purpose but is not as widely recognized as a Class B additive compared to AFFF.