What type of extinguishing agent is used in Class B fire extinguishers?

Class B fire extinguishers are specifically designed to combat fires that involve flammable liquids and gases, such as oil, gasoline, paints, and solvents. The use of foam or chemical agents is crucial because these materials work to suppress the fire by forming a barrier that prevents oxygen from reaching the fuel and cools the fire, helping to extinguish it effectively.

Foam agents smother the ignited liquid surface, reducing the chance for vapors to escape and ignite, while dry chemical agents interrupt the chemical reaction taking place in the fire. This is why foam or chemical agents are the appropriate choice for Class B fires, making this option the correct answer.

Understanding the nature of the fire and the composition of the extinguishing agent is vital for effective fire management, as using the wrong type of extinguishing agent on a Class B fire can exacerbate the situation instead of mitigating it.