What is the primary function of a dry chemical extinguisher?

The primary function of a dry chemical extinguisher is to interrupt the combustion process. Dry chemical extinguishers contain agents, such as monoammonium phosphate, which work by forming a barrier between the fuel and the oxygen, thereby breaking the chemical reaction necessary for fire to continue burning. This is particularly effective on various types of fires, including those fueled by flammable liquids or gases.

Each fire requires three components—fuel, heat, and oxygen—to sustain a flame, often referred to as the fire triangle. By targeting the chemical chain reaction that occurs during combustion, dry chemical extinguishers can effectively put out the fire without needing to cool down the flames directly, which is the function of water-based extinguishers.

While removing oxygen and stopping chemical reactions are important aspects in fire suppression, the specific action of dry chemical extinguishers focuses on interrupting the combustion sequence itself. This makes them versatile and effective for different classes of fires, particularly Class B and C fires.