Which of the following best describes Class C fires?

• A. Wood, cloth, paper
• B. Grease and solvents
• C. Wiring and electrical equipment that are energized
• D. Magnesium and other reactive metals

Answer: (C)

Fire in energized electrical equipment is what Class C covers. The key idea is that electricity is involved, so using the wrong extinguisher—like water—can conduct electricity and cause shocks or spread the fire. The safer approach is to use nonconductive extinguishing media (such as carbon dioxide or dry chemical powder) and, if safe to do so, shut off the power before fighting the fire. Once the equipment is de-energized, the fire may be addressed with an extinguisher appropriate for the materials involved.

The other descriptions point to different fire classes: wood, cloth, and paper are ordinary combustibles (Class A); grease and solvents are flammable liquids (Class B); magnesium and other reactive metals are metal fires (Class D).