Is it acceptable to mix Class A and Class B foam?

Mixing Class A and Class B foam is not acceptable because these foam types are chemically distinct and designed for different purposes. Class A foam is primarily used for enhancing the water's ability to penetrate solids and is effective in fighting structural fires, while Class B foam is formulated to suppress flammable liquid fires by creating a blanket that separates the fuel from the air. When mixed, their individual effectiveness can be compromised, potentially leading to inadequate fire suppression and safety risks during firefighting operations. Therefore, the recommendation is to use each type of foam according to its intended application to ensure optimal performance and safety.