What Is a Fire Extinguisher?

A fire extinguisher is a device used to put out a fire. It contains an agent that is intended to extinguish a fire by smothering it, either by absorbing heat or by destroying the chemical reaction that causes the fire.

Water is a common extinguishing agent, but other chemicals are also available. These vary in cost, stability and toxicity, as well as ease of use and cleanup.

Some of the most common are a dry chemical foam, such as sodium bicarbonate (ordinary baking soda), or potassium carbonate, and a vaporizing agent such as carbon dioxide. These are both effective on Class B and C fires, because the agents smother the flame by driving oxygen away from the fuel source.

Another popular agent is water mist, which cools the flames and prevents them from spreading. This type of extinguisher is used mainly on cooking fat and oil fires in kitchens, but can also be useful for other types of fire as well.

Other dry chemical fire extinguishers are based on monoammonium phosphate (MAP) or on chlorine or carbon dioxide. These are more expensive than dry chemical foam or water mist, but they have been known to be able to kill certain types of fire.

MAP is effective on Class B and C fires because it releases a cloud of carbon dioxide that smothers the flame by driving oxygen away from the fuel. This gas also prevents the formation of flammable gases and the combustible by-products, such as acetone, which can cause serious burn injuries.

Many fires, particularly those in industrial environments, are fueled by electrical energy. A fire extinguisher that has passed a 35 kV dielectric test, and that has been labeled to be safe for use on live electrical equipment, can be very helpful in this situation.

This is especially true of fires in high-risk electrical installations, such as power plants, hospitals and other industrial areas. The electrical hazard may be present even if the electricity is switched off, so it is important to have a properly fitted and tested fire extinguisher on hand.

The choice of the right extinguisher could literally save your life. It is therefore essential to check the fire classification and the colour code of the fire extinguisher before using it.

Portable fire extinguishers are generally fitted in buildings at an easily accessible location, such as against a wall in a high-traffic area or on a main walkway. They are also commonly fitted to motor vehicles and aircraft.

Fire safety regulations in the UK and other countries require that all businesses have at least one fire extinguisher in a suitable position and carry out regular maintenance to ensure it is working safely. This should include fire protection training and ensuring the person in charge knows where the extinguisher is and how to use it.

Some fire extinguishers have a colour code for the specific type of fire they are designed to handle, which can be helpful in deciding which ones to buy and where to store them. The extinguisher’s colour code will indicate whether the fire extinguisher is suitable for class A, B or C fires.