Carbon dioxide is used to put out what class of fires?

• A. Class A
• B. Class B
• C. Class D
• D. Class B or C

Answer: (D)

Carbon dioxide extinguishes by displacing the oxygen and blanket­ing the fire, smothering it without leaving a residue or conducting electricity. This makes it especially effective on fires involving flammable liquids and energized electrical equipment. So CO2 is well suited for Class B fires (flammable liquids) and Class C fires (electrical equipment). It’s not the best choice for Class A ordinary combustibles in open spaces, where it can’t cool or reach hidden pockets, and it doesn’t work for Class D metal fires. That’s why the answer is Class B or C.