Carbon dioxide is effective on which fire types?

• A. Class B and Class C
• B. Class A only
• C. Class A and Class B
• D. Class C only

Answer: (A)

Carbon dioxide extinguishes fires by displacing the surrounding air, choking off the flame without adding heat or leaving residue. This makes it particularly effective for fires involving flammable liquids and energized electrical equipment. For Class B fires (flammable liquids), the lack of oxygen around the vapors prevents burning. For Class C fires (electrical equipment), CO2 is nonconductive, so it can suppress the flame without conducting electricity. It’s less effective on Class A fires (ordinary combustibles) because those fires rely more on heat absorption and cooling of the fuel, and the CO2 can dissipate before fully stopping the burn.