What is a Fire Extinguisher?

A fire extinguisher is a handy tool that can be used to put out a small fire before it gets out of hand. Its contents vary, depending on the type of fire it’s designed to fight, but all have one thing in common: they contain a pressurised chemical that will put out a fire.

Fire extinguishers have two parts – a nozzle or hose and a release lever, also known as a trigger or handle. When you pull this lever, it releases the fire extinguishing agent and directs it at the fire. Most fire extinguishers use water, foam or dry powder to suppress a fire, but they all have the same basic mechanism of discharging their content when you squeeze the handle or trigger.

The first fire extinguisher developed was the Buffalo M-X liquid (developed during World War II), which cooled and smothered magnesium fires. It was easy to operate from a portable unit and did not damage electrical items. After the war, the British company Ansul produced a more sophisticated hand-held unit based on carbon dioxide gas (CO2) to tackle class B and C fires. This is effective because the carbon dioxide suffocates the fire by blanketing it and displaces oxygen, which is essential for combustion.

Another type of hand-held fire extinguisher uses a special type of graphite powder to smother metal fires, such as aluminium or titanium (G-Plus, G-1, Lith-X and Chubb Pyromet). It is not suitable for classes A or D fires because the metal will react explosively with water. However, some manufacturers have developed a special low-velocity nozzle or discharge wand to avoid disrupting the finely divided metal particles in a burning magnesium and titanium fire.

Sodium chloride (ABC dry chemical) was the most popular and successful hand-held extinguisher until the late 1950s, when the Ansul company released its cartridge-operated ABC fire extinguishers. The nozzle of the Ansul ABC extinguishers has a diamond-shaped hole that can penetrate a class A fire and a narrow aperture for directing the spray to the bottom of the fire. These can also be used on a metal-fuelled cooking fire.

Newer, handheld water mist extinguishers use an ultra-fine mist of microscopic demineralised water particles that quickly stops the fire by smothering it and cooling the fuel. They can be used on classes A, B and C fires and are especially useful in a kitchen, where they have a high usage rate. These have a tamper-proof seal and are very lightweight. Like all other types of hand-held fire extinguishers, you should keep these clean and in good working order by inspecting them monthly. Check the pressure level, nozzle clogs and corrosion, and make sure there are no visible signs of wear and tear. You should also make sure they are easily accessible so they can be used in an emergency. It’s important to follow the PASS system when using your fire extinguisher – Pull, Aim, Squeeze and Sweep. Once you have used the fire extinguisher, be sure to leave the area and call the fire department if necessary.