Fires involving combustible metals such as zirconium, sodium, or potassium are which class?

Fires involving combustible metals such as zirconium, sodium, or potassium are which class?

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

Answer: (D)

Fires involving combustible metals are Class D fires because the fuel is the metal itself and these fires behave very differently from ordinary combustibles, liquids, or electrical fires. Metals like zirconium, sodium, and potassium burn in air and can react violently with water or standard extinguishing agents. Water can cause explosive or out-of-control reactions with these metals, so it’s not used. Instead, you apply a specialized dry powder extinguishing agent designed for metal fires. The powder blankets the metal, isolates it from air, and absorbs heat, slowing or stopping the oxidation reaction. That combination of suppressing the heat and starving the reaction makes Class D the appropriate designation for these fires. Not the other classes, which cover ordinary combustibles, flammable liquids, or energized electrical equipment.

Fires involving combustible metals are Class D fires because the fuel is the metal itself and these fires behave very differently from ordinary combustibles, liquids, or electrical fires. Metals like zirconium, sodium, and potassium burn in air and can react violently with water or standard extinguishing agents. Water can cause explosive or out-of-control reactions with these metals, so it’s not used. Instead, you apply a specialized dry powder extinguishing agent designed for metal fires. The powder blankets the metal, isolates it from air, and absorbs heat, slowing or stopping the oxidation reaction. That combination of suppressing the heat and starving the reaction makes Class D the appropriate designation for these fires. Not the other classes, which cover ordinary combustibles, flammable liquids, or energized electrical equipment.