Which dry chemical agent is used to fight Class A fires?

Which dry chemical agent is used to fight Class A fires?

• A. Potassium bicarbonate
• B. Sodium bicarbonate
• C. Monoammonium phosphate
• D. Calcium carbonate

Answer: (C)

Fires involving ordinary combustibles need both cooling and a barrier to keep oxygen from reigniting the fuel. Dry chemical powders can interrupt the flame chemistry and form a protective coating on the fuel surface. Monoammonium phosphate is particularly effective because it coats the fuel with a cohesive layer that both cools and insulates, helping prevent re-ignition. This makes it a versatile choice for extinguishers rated for common combustibles, as well as for other fire types. The other powders are generally more focused on liquid fuels or electrical fires and don’t provide the same robust coating on solid fuels, so they’re not as effective for Class A fires. Calcium carbonate is less common in modern extinguishers and also not as versatile as MAP.

Fires involving ordinary combustibles need both cooling and a barrier to keep oxygen from reigniting the fuel. Dry chemical powders can interrupt the flame chemistry and form a protective coating on the fuel surface. Monoammonium phosphate is particularly effective because it coats the fuel with a cohesive layer that both cools and insulates, helping prevent re-ignition. This makes it a versatile choice for extinguishers rated for common combustibles, as well as for other fire types. The other powders are generally more focused on liquid fuels or electrical fires and don’t provide the same robust coating on solid fuels, so they’re not as effective for Class A fires. Calcium carbonate is less common in modern extinguishers and also not as versatile as MAP.