What material is commonly used in Class B fire extinguishers?

The material commonly used in Class B fire extinguishers is dry chemical. Class B fire extinguishers are specifically designed to combat fires involving flammable liquids such as gasoline, oil, and grease. Dry chemical agents, such as monoammonium phosphate, work effectively by interrupting the chemical reaction that fuels the fire. They form a barrier between the oxygen and the fuel, thereby extinguishing the flame.

While foam and carbon dioxide are also used in certain types of fire extinguishers, they are more commonly associated with other fire classes. Foam is effective for Class B fires as it can smother the fire and prevent re-ignition, but it is not the primary agent typically referred to in this context. Water is only suitable for Class A fires involving solid combustibles and is ineffective and potentially dangerous for flammable liquid fires, which defines the parameters for Class B extinguishers.