What Is a Fire Extinguisher?

A fire extinguisher is a portable device that puts out small fires by directing a stream of water or a special liquid or foam material onto the flames. It can also suffocate the flames by denying them oxygen or interfering with the chemical reactions that make them burn. These devices are available in businesses, homes, schools and other places where a fire could occur. They’re easy to use and typically cost less than $10,000 each.

A few things to keep in mind about fire extinguishers are that the type you choose must match the type of fire you’re trying to put out, and that the device must be aimed at the base of the flames (not above or to the side). They’re usually color-coded with a red stripe and a number. Each device has a tank that contains the extinguishing agent and has a handle with a pressure gauge on top. A discharge lever near the top releases the extinguishing agent through a discharge hose, and you must shake the device vigorously before using it. You can find these devices in two forms: handheld units that weigh from 0.5 to 14 kilograms (30.9 to 30.9 lb) and cart-mounted models, which have a red wheel and are typically hung on the wall or placed on a stand.

Carbon Dioxide (CO2) extinguishers discharge a gas that reduces the oxygen level in the atmosphere and thus suffocates the fire. They’re effective against Class A fires, such as wood, paper, cloth and trash. They’re also used against Class B flammable liquids, such as grease, oil and paint, and for gasses, including butane and propane.

Clean Agent Fire Extinguishers (CAF) discharge a clean, nonconductive agent that is not harmful to electronic equipment and does not leave any residue after use. These extinguishers are often used in computer rooms and other places with expensive equipment. The agent inside these devices is typically bromochlorodifluoromethane, which is similar to Halon (which was phased out because of its damaging effect on the environment), and has about twice as much range as carbon dioxide on a weight-of-agent basis.

Powder Fire Extinguishers

These devices contain a dry powder that smothers the flames by separating them from oxygen, so they don’t burn. They’re used against Class A and Class B fires, but don’t work on combustible metals like magnesium, titanium, sodium and potassium, which are found in engineering factories.

AFFF and FFFP Fire Extinguishers

These extinguishers are designed to tackle Class A and Class B fires by discharging a liquid-like substance that can smother the flames and block their path to oxygen. These extinguishers are effective for a long time after they’re used, and can be used in freezing temperatures.

There are many other types of fire extinguishers, including halon-based ones, but these three are the most common. Regardless of the fire extinguisher you choose, it’s important to check your unit frequently and follow its manufacturer’s instructions for maintenance. Also, remember to always keep it within reach, as the fire may quickly spread and block your escape route.