Types of Fire Extinguishers

A fire extinguisher is a portable device that can be used to put out small fires before they have time to spread. There are many different types of fire extinguishers, and they can be grouped into different categories based on their primary uses. The main goal of a fire extinguisher is to provide an immediate means to stop the spread of fire until it can be put out with other methods, such as exiting the area or activating the fire alarm.

Most fire extinguishers are available in a variety of sizes, but the most common type is the Class A model. It contains dry powder that is effective against wood, paper, cloth and some plastics. These types of fires are relatively easy to control.

Another popular type is the carbon dioxide (CO2) fire extinguisher, which is a clean agent that removes oxygen from the flames and prevents them from reigniting. Its operation is similar to that of an ABC extinguisher: pull the pin, aim at the base of the fire and sweep from side to side. It is effective against Class A, B and C fires.

A wet chemical fire extinguisher is a pressurised solution of alkali salts in water and can be used on Class A and some Class B fires. It dispenses a fine mist which cools the flames and allows it to penetrate deeper into the fuel to remove heat, preventing reignition. This type of fire extinguisher is commonly found in kitchens with deep fat fryers.

Wet chemical (WF) and AFFF models are also suitable for Class F fires, which are flammable liquids with an autoignition temperature above 100°C. They contain a combination of chemicals including potassium acetate, potassium carbonate, potassium citrate and others, which have the ability to coagulate and seal the surface of the liquid fuel, preventing its ignition. Unlike a water mist extinguisher, these types of fire extinguishers can be discharged at lower temperatures to stop the fire without causing splashing or cooling effects on bystanders.

Graphite-based fire extinguishers (G-Plus, G-1, Lith-X) contain dry graphite that smothers metal fires. They were first designed for magnesium, but they will work on other Class B metal fires as well. They are not effective on flowing or vertical metal fires, such as those caused by lithium battery fires.

There are also specialty extinguishers for fighting pyrophoric (ignites on contact with air) liquid fires such as gasoline and propane. These types of fires are often caused by sparks from electrical devices or mechanical equipment. A MET-L-KYL / PYROKYL fire extinguisher contains sodium bicarbonate and silica gel particles to interrupt the chain reaction of these ignitable liquids and absorbs any unburned fuel, preventing its contact with air.

All hand-held fire extinguishers should be maintained regularly. A basic service should be carried out annually, during which the weight of the extinguisher is checked to ensure that it is at its correct pressure. The hose, dip tube and handle are also inspected for signs of damage or corrosion. A more detailed examination is required for cartridge and wet chemical extinguishers, which require a service every five years, during which they are opened up to check the internal weight of the agent and tested for any signs of deterioration.