Different types of extinguishing agents have different modes of action, and certain ones are only appropriate for specific fire classes.

This is a powder-based agent that extinguishes by separating the three parts of the fire triangle. It prevents the chemical reactions involving heat, fuel, and oxygen, thus extinguishing the fire. During combustion, the fuel breaks down into free radicals, which are highly reactive fragments of molecules that react with oxygen. The substances in dry chemical extinguishers can stop this process.

Internationally there are several accepted classification methods for hand-held fire extinguishers. Each classification is useful in fighting fires with a particular group of fuel.