What Extinguishing Agents are used in a Fire Extinguisher?

Do you know the different types of extinguishing agents? Brush up on your extinguishing agents using this summary of extinguishing agents used in fire extinguishers.

Dry Chemical.

This agent is made up of very small particles of sodium bicarbonate, potassium bicarbonate, or ammonium phosphate with additives to help enhance flow and prevent packing and caking. Extinguishers with sodium bicarbonate and potassium bicarbonate are rated for Class B and Class C fires. Extinguishers with ammonium phosphate are rated for Class A, B, and C fires.

Wet Chemical.

This is agent is a water solution with additives that chemically react with fats in a cooking-oil fire, creating a thick foam blanket that will float on the surface of the oil. These extinguishers are intended for Class K fires.

Clean Agent.

This electrically nonconductive extinguishing agent, evaporates and leaves no residue behind. The currently acceptable clean agents used in extinguishers include halocarbons, such as Halotron I and FE36, Halon 1211, and carbon dioxide. Carbon dioxide extinguishers are rated for Class B and C fires. Extinguishers containing halocarbons and Halon 1211 are rated for Class B and C fires, while larger units are rated for Class A fires.

Water Stream (extinguisher).

This is an extinguisher with a 2.5 gallon capacity, containing tap water or a loaded stream charge that is discharged through a hose as a solid stream. This type of extinguisher is rated 2-A for use on Class A fires only.

Water Mist (extinguisher).

An extinguisher with a special nozzle for discharging de-ionized water as a fine mist. This type of extinguisher is rated for Class A and C fires.


This extinguishing agent is either aqueous film-forming foam (AFFF) or film-forming fluoroprotein (FFFP) foam. Extinguishers containing foam solution have a hose with a special nozzle that introduces air to the solution, which creates foam as it leaves the extinguisher. Foam extinguishers are intended for Class B fires.

Dry Powder.

This extinguishing agent is made up of powder or granular particles that are intended for the extinguishment of Class D combustible metal fires. Typical dry powder agents include sodium chloride, graphite, and copper. Extinguishers containing dry powder are listed for the extinguishment of specific combustible metals.

With the help of this summary, you can now discuss portable fire extinguisher applications more confidently with your customers. Selecting the proper extinguishing agent for any application is dependent on your understanding of its material.

For extinguisher placement, always follow NFPA or locally adopted standards and consult with the Authority Having Jurisdiction (AHJ) as needed.