Which statement correctly characterizes Class B fires?

• A. They involve ordinary combustibles
• B. They involve flammable liquids
• C. They involve electrical equipment
• D. They involve reactive metals

Answer: (B)

Class B fires are fires that involve flammable liquids. This includes liquids like gasoline, solvents, and oils, whose vapors can ignite and spread across surfaces, making these fires distinct from others. Because the fuel is a liquid, the goal is to remove heat, separate the fuel from the heat source, or interrupt the vapor, using extinguishing agents such as foam, dry chemical powders, or CO2. Water is generally avoided on flammable liquids because it can spread the liquid and spread the fire. Fires with ordinary combustibles (like wood or paper) are Class A and are typically fought with water or foam; electrical fires (Class C) require non-conductive extinguishing methods and de-energizing the equipment; and fires from reactive metals (Class D) need specialized dry powders. Thus, identifying flammable liquids as the agents involved correctly characterizes Class B fires.