Water extinguishers should never be used on which class of fires?

Water extinguishers should never be used on which class of fires?

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

Answer: (D)

Water extinguishers are effective for ordinary combustibles and can be used on some electrical fires, but they are not suitable for fires involving reactive metals. When water encounters burning metals such as magnesium, sodium, potassium, or certain titanium alloys, a violent exothermic reaction occurs, producing hydrogen gas and steam. This can cause an explosion, splatter burning metal, and continued or intensified ignition. To safely suppress metal fires, specialized dry powder extinguishing agents are used; they smother the fire and absorb heat without triggering a dangerous chemical reaction. So, water should never be used on metal fires.

Water extinguishers are effective for ordinary combustibles and can be used on some electrical fires, but they are not suitable for fires involving reactive metals. When water encounters burning metals such as magnesium, sodium, potassium, or certain titanium alloys, a violent exothermic reaction occurs, producing hydrogen gas and steam. This can cause an explosion, splatter burning metal, and continued or intensified ignition. To safely suppress metal fires, specialized dry powder extinguishing agents are used; they smother the fire and absorb heat without triggering a dangerous chemical reaction. So, water should never be used on metal fires.