What does a dry chemical fire extinguisher do when it is discharged?

A dry chemical fire extinguisher effectively interrupts the combustion process by creating a barrier between the fuel and the oxygen, which is essential for fire to burn. The dry chemical agent often contains compounds like monoammonium phosphate, sodium bicarbonate, or potassium bicarbonate, which, when discharged, form a layer over the fuel surface. This layer helps to suppress the combustion process by inhibiting the chemical reactions that occur between the fire's fuel and its oxygen supply.

While cooling the burning material is a method used by certain types of extinguishers (like water-based ones), it is not the primary action of dry chemical extinguishers. Similarly, dispersing water does not apply here, as these extinguishers do not use water as an extinguishing agent. Lastly, while some extinguishing agents may release gases to smother a fire, dry chemical extinguishers primarily function through the formation of a barrier rather than smothering with gas.