Types of Fire Extinguishers

A fire extinguisher is a hand-held device that can be used to fight small fires. It is a vital safety tool to have at home and in the workplace. Several different types of fire extinguishers exist, each designed for a specific class of fire. Each fire extinguisher type works by differently absorbing or discharging substances. It is important to choose the correct fire extinguisher type for a fire because using the wrong one can make the fire worse or even cause injury to the user.

The basic design of a fire extinguisher is similar regardless of the type: it has a pressure gauge and a metal handle with a pin at the top. A hose or wand extends down from the handle and is attached to a discharge mechanism that can be operated by pulling the pin. The discharge nozzle is aimed at the base of the fire and the user sweeps it across the fire in an arc until the flames are extinguished. Some models also have a jet nozzle instead of a spray nozzle for use on liquid fires.

Class A fire extinguishers absorb organic solids, class B fires absorb flammable liquids (excluding cooking oils and fats), and class C fires involve combustible gases. These fires can be put out with water or a water-based chemical compound.

Class D fire extinguishers smother fires involving metals, including magnesium, titanium, zirconium, sodium, and lithium. They contain a powdered graphite that cools and smothers the fire, unlike copper-based or sodium chloride based dry powders.

Stream and foam fire extinguishers use liquid compounds to cool the surface of a fire, which can prevent re-ignition or trap hot metals in a melted and vaporized state. The hoses are flexible to reach deep into crevices, and they can be used from a standing position. Foam extinguishers are used on classes A and B, and some have a higher concentration of concentrate than a stored-pressure pre-mix model to extinguish class C fires.

Halon gas fire extinguishers use a gas that inhibits the chemical reaction between the fuel and oxygen to stop the fire. This fire extinguisher type is no longer available in new units because of its ozone depleting effects, but it can be recycled and refilled into existing cylinders by Amerex and Badger. Alcohol-resistant aqueous film-forming foams (AFFF) extinguishers use a foam to extinguish polar solvent and other water-miscible fuels. Previously, these were produced as solid-charge models that contained the AFFF concentrate inside an external cartridge and discharged through an air-aspirating nozzle. They now come only in pre-mix forms, where the AFFF is stored mixed with water at discharge pressure.