What kind of agent is used in a dry chemical fire extinguisher?

A dry chemical fire extinguisher primarily uses agents like sodium bicarbonate or monoammonium phosphate to suppress fires. These agents are effective for a variety of fire classes, particularly Class B (flammable liquids) and Class C (electrical) fires. Sodium bicarbonate acts by releasing carbon dioxide upon heating, which helps to smother the flames by cutting off the oxygen supply, while monoammonium phosphate is a versatile agent that can interrupt the combustion process and prevent re-ignition.

In contrast, other choices represent different types of fire extinguishing agents that are not used in dry chemical extinguishers. Water or foam is typical for Class A fires and is not suited for flammable liquids. Carbon dioxide or halon agents are primarily used in specific circumstances, such as for electrical fires, but don't fit the classification of dry chemical FIRE extinguishers. Gel or powder additives could be included in other types of extinguishers but do not categorize as dry chemical agents. By identifying the correct use of sodium bicarbonate and monoammonium phosphate, one can understand their effectiveness in extinguishing fire types where dry chemical agents are most applicable.