Classification of Fire Extinguishers

Fire extinguishers are the tools that allow you to fight a fire before it grows out of control. Using one requires training and confidence under pressure, but the right extinguisher is key to keeping a fire from spreading while you work on it. The type of fire you’re trying to extinguish determines the kind of extinguisher you need. There are five classes of fires, and each extinguisher is marked with standard symbols or letters to indicate what class it can put out.

A fire extinguisher works by coating the fuel with a powder, separating it from oxygen and interrupting its chemical reaction. Dry chemical extinguishers are found in cylinders that hold from 5 to 20 pounds of monoammonium phosphate, a finely ground extinguishing agent that looks like yellow talcum powder. They’re effective on Class A and Class B fires but messy to use. They can be used by pulling the pin, aiming at the base of the fire, and sweeping the nozzle from side to side. They have a range of about 15 feet.

APW or water extinguishers have a hard horn at the end of a flexible hose, and they’re useful for Class A fires of wood, paper, cloth, and most plastics. They cool the fire and displace the oxygen that supports it, but they’re ineffective on electrical fires because the water can also damage electronics.

CO2 extinguishers have a red cylinder containing pressurized carbon dioxide gas, which is nonflammable and leaves no residue. They’re handy for class B and class C fires of flammable liquids and electric equipment, and they can be effective on a small area of a fire that hasn’t spread very far.

Dry powder extinguishers are a popular choice for class B and class C fires, particularly those in office buildings. They’re available in sizes ranging from hand-held models to cart-mounted units that can be used on larger areas of flames. You can operate them by pulling the pin, removing the hose and wand assembly from the retainer, aiming at the base of the fire, squeezing the lever slowly and evenly, and sweeping the nozzle from side-to-side. They have a range of about 15 to 20 feet.

The National Fire Protection Association recommends locating fire extinguishers in areas where they’re easily accessible. It’s best to install them on walls or in the ceiling rather than on the floor, so you can reach them quickly when a fire breaks out. You should also position them so they’re not blocked by furniture or other obstacles. If you plan to place them on a wall, they should be no higher than 48 inches from the ground. This ensures that you can access them when it’s time to recharge or reposition them.

When you’re working with a fire, it’s important to keep in mind that any sort of combustion produces toxic smoke that can choke you and prevent your ability to use the extinguisher. If you can’t see clearly, or if the fire is growing rapidly, you should evacuate and let the fire department handle it.