Generally, water should not be used to extinguish which class of fires?

Generally, water should not be used to extinguish which class of fires?

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

Answer: (D)

Water is great at cooling ordinary combustibles, but it’s dangerous with fires involving reactive metals. When reactive metals meet water, they can generate a lot of heat and hydrogen gas; that hydrogen can ignite and the rapid steam production can eject burning metal, spreading the fire or causing an explosion. Because of this reaction risk, water should not be used on metal fires. Instead, extinguishing agents designed for metal fires (Class D) are used, often with specialized powders or materials that smother the metal without reacting.

Water is great at cooling ordinary combustibles, but it’s dangerous with fires involving reactive metals. When reactive metals meet water, they can generate a lot of heat and hydrogen gas; that hydrogen can ignite and the rapid steam production can eject burning metal, spreading the fire or causing an explosion. Because of this reaction risk, water should not be used on metal fires. Instead, extinguishing agents designed for metal fires (Class D) are used, often with specialized powders or materials that smother the metal without reacting.