What kind of fires are not effectively controlled by foam?

The effectiveness of foam as a fire suppression agent varies by the class of fire. Foam is primarily designed to combat Class B fires, which involve flammable liquids. It works by forming a barrier between the fuel and the air, thus suffocating the fire and preventing re-ignition.

Class A fires, which involve ordinary combustibles such as wood and paper, can be effectively managed with foam, though water is typically more common for extinguishing these types of fires. Class D fires, which involve combustible metals, also cannot be extinguished with foam, but they are classified differently from Class C fires.

Class C fires involve energized electrical equipment. Foam is not suitable for these types of fires because it is electrically conductive and can pose serious safety hazards. If foam were used in a Class C situation, it could lead to the risk of electrocution for firefighters and may not effectively suppress the fire at all. Understanding the types of fires and the appropriate suppression methods is crucial for effective fire management and safety.