Types of Fire Extinguishers

A fire extinguisher is a valuable tool in fighting small fires in your home. But before you use it, it is important to know what type of fire your extinguisher is rated for and how to operate it. Also, make sure it is located where you can access it quickly and that everyone in the family knows where it is. This way, you can deploy it before the fire gets too out of hand and you’re not trapped in a smoke-filled room.

Fire extinguishers are generally categorized into three groups: powder-based, liquid-based and foam-based. These are the types that most people are familiar with, but there are some other less common types, such as carbon dioxide and water-based suppressants.

Dry chemical extinguishers use an agent such as monoammonium phosphate, often referred to as ABC or tri-class, to separate the fire’s fuel, heat and oxygen and thus stop the chemical reactions that cause the fire to burn. They can be used on Class A, Class B and Class C fires.

Water-based fire extinguishers use a spray of water to cool and smother the fire, which can be particularly effective on electrical equipment or combustible metals. They have a low power and limited range, so they are typically used on smaller fires.

The simplest form of water-based fire extinguisher is a pressurized container filled with water, which is discharged by a jet nozzle. It can be particularly effective on small electrical fires, as it is not corrosive to electronic components and does not leave any residue.

Foam-based fire extinguishers smother the flames by blocking oxygen and prevents reignition, but are ineffective on burning fats and oils (Class K). They use a combination of chemicals such as sodium bicarbonate, potassium citrate or sodium carbonate to produce a thick foam that seals the fire and excludes air.

Aqueous film-forming foam (AFFF) is the most widely used type of fire suppressant in airport runways, heliports and docks. It can be used on Class A and Class B fires, but it also has a vapor suppression capability for hazmat incidents.

Clean agents are nonconductive and noncorrosive, so they can be used on delicate and expensive electronic equipment. They discharge as a gas/mist or liquid, and quickly evaporate after use with about twice the range of carbon dioxide. They are also effective on Class B and Class C fires, making them practical for office or large computer equipment rooms.

Unlike other extinguishers, carbon dioxide does not contain any chemical and is therefore non-toxic to humans. It is also the only fire extinguisher listed for use on Class A, Class B and Class C, and can be safely used by the elderly or children. These extinguishers are usually designed with a hose/nozzle, but some are also available with a hand wand for use on hard-to-reach or inaccessible fires.