Which class of fire involves combustible metals such as magnesium and sodium?

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

Answer: (D)

Fires involving metals burn in a way that’s different from ordinary combustibles or liquids. Combustible metals like magnesium and sodium are highly reactive and can react violently with water or many common extinguishing agents, sometimes producing hydrogen gas or an explosion. Because of these unique hazards, they’re treated as a separate fire category. The correct way to fight these fires is with a dry powder extinguisher specifically rated for metal fires. The powder blankets the metal, absorbs heat, and isolates the fuel from air, cooling and smothering the fire without triggering dangerous reactions. Water, foam, or CO2 can worsen metal fires, so they’re avoided. In practice, responders in a facility should use the appropriate metal-fire powder and call for specialized assistance if the blaze is large. Other fire classes cover ordinary combustibles, flammable liquids, and electrical equipment, which don’t address the risks of metal fires.