Fire extinguishers are probably the most common fire fighting equipment known to man for fire extinguishing. They are portable and can be operated easily by almost anyone, not just skilled firefighters. As the name implies, a fire extinguisher is a device used to extinguish or control small fires, often in emergency situations. It consists of a metal cylinder which contains water or fire-retardant chemicals at high pressure. Fire extinguishers are not designed to be used on wildfires or out-of-control fires. They are usually fitted in buildings, automobiles and aircrafts at easily accessible locations.
Fire Extinguishing: Components Of A Fire Extinguisher
A typical fire extinguisher has five major components— a cylindrical tank, a valve assembly, a hose and/or a nozzle, an extinguishing agent and a propellant.
It is the largest and most noticeable part of a fire extinguisher. It is responsible for storing the extinguishing agent and the propellant under the correct amount of pressure. Fire extinguisher tanks are typically made of steel and can be quite heavy.
The valve assembly consists of a handle that enables users to grasp, lift and transport the extinguisher; a locking pin to prevent accidental discharge, the dip tube through which the extinguishing agent is drawn up for expulsion, and a release lever.
A nozzle helps the user control where the extinguishing agent is directed or aimed at. A hose is typically found on extinguishers that are heavier than 3 kg, it allows the user to aim the extinguishing agent at the fire with more precision.
This is probably the most important component of a fire extinguisher. It is the substance that is discharged from the extinguisher to suppress or extinguish a fire. The different types of extinguishing agents available are explained in the next section.
This is a gas whose function is to expel or force the extinguishing agent from the fire extinguisher. Compressed nitrogen is often used.
If you wish to know about other types of fire fighting equipment. Read this article.
Fire Extinguishing: Types Of Fire Extinguishers
Fire extinguishers are usually classified according to the type of extinguishing agent they contain. There are five main types of fire extinguishers—Water, Foam, Dry Powder, Carbon Dioxide (CO2) and Wet Chemical extinguishers. In order to determine which type of fire extinguisher is suitable for a particular situation, an understanding of the different classes of fire is required. There are six known classes of fire.
- Class A – this involves fire with solid materials such as wood, paper or textiles.
- Class B – this involves fire with flammable liquids such as petrol or diesel.
- Class C – this involves fire with gases.
- Class D – this involves fire with metals.
- Class E – this involves fire with equipment.
- Class F – this involves fire with cooking oils or fats.
It is dangerous to attempt combating all the different classes of fire with one type of fire extinguisher, discharging the wrong extinguishing agent on a fire may cause the fire to spread instead of extinguishing it. Learn more about the different types of extinguishers and their uses below:
Fire Extinguishing: Types of Fire Extinguishers and Their Uses
- Water Extinguishers
- Foam Extinguishers
- Dry Powder Extinguishers
- Carbon Dioxide Extinguishers
- Wet Chemical Extinguishers
Fire Extinguishing: Water Extinguishers
They are highly effective against class A fires i.e. fires involving flammable solids like wood, paper or textiles. They are not suitable for combating other classes of fire, especially fires involving electrical equipment. Standard water extinguishers are highly affordable and easy to use, they suppress fires by soaking the combusting materials with water. Some water extinguishers contain chemical additives that improve their effectiveness by up to 300%.
Water mist extinguishers, a new category of water extinguishers, are suitable for putting out nearly all classes of fire (A, B, C, E and F), but they are highly expensive. They contain deionized water which is incapable of conducting electricity, hence, they are more effective than regular water extinguishers against electrical fires.
These are extinguishers that utilise foam as the primary extinguishing agent. They put out fires by creating a blanket of foam that smothers the fire and seals in flammable vapours, preventing reignition. Foam extinguishers are effective against fires involving flammable solids and liquids (Class A and B fires). When used against class A fires, the user can simply point and spray. However, when used against class B fires, they should not be sprayed directly into the burning liquid, the foam should be sprayed nearby so that it can build up and flow across the liquid.
Dry Powder Extinguishers
Dry powder extinguishers are commonly known as ABC extinguishers because they are highly effective against class A, B, and C fires. They typically contain a fine chemical powder composed of mono ammonium phosphate. Dry powder extinguishers put out flames by coating the burning material with a thin layer of dust, thereby separating the fuel from the oxygen in the air. They should not be used in enclosed spaces because the powder can easily be inhaled and it leaves a residue that is difficult to clean up.
A special kind of dry powder extinguisher known as a Class D extinguisher is suitable for extinguishing class D fires.
Carbon Dioxide Extinguishers
Carbon dioxide extinguishers are primarily used to put out electrical fires. Electrical fires were the major cause of fire incidents in Nigeria in 2021.
They are also effective against class B fires. They are filled with pressurized carbon dioxide gas, thus, they leave no residue after use. The carbon dioxide works by displacing the oxygen around the fire. Carbon dioxide extinguishers are not suitable for outdoor use, they are ideal for offices, workshops, and other places where electrical equipment or devices are used. Due to the extremely cold temperature of the carbon dioxide, the user must avoid contact between the CO2 discharge and bare skin.
Wet Chemical Extinguishers
Wet chemical fire extinguishers are suitable for putting out fires that involve cooking oils and fats (Class F fires). They are ideal for professional kitchens, as well as home kitchens. They consist of a pressurized solution of alkali salts in water, which, when discharged, creates a fine mist, cooling the flames and preventing splashing. The best method of application is to spray in slow circular motions. The user may have to empty the contents of the extinguisher on the fire to prevent reignition.
Fire Extinguishing: How To Properly Operate A Fire Extinguisher
If a fire extinguisher is not operated correctly, the fire may spread and become out of control, thus, it is important to learn how to properly put out a fire with a fire extinguisher. There are four basic steps involved:
- Pull: Pull the pin at the top of the extinguisher to break the seal.
- Aim: Approach the fire standing at a safe distance and aim the nozzle towards the base of the fire.
- Squeeze: Squeeze the handles together to discharge the extinguishing agent inside. To stop the discharge, release the handles.
- Sweep: Sweep the nozzle from side to side as you approach the fire, directing the extinguishing agent at the base of the flames.
Fire extinguishers have been saving lives and property for centuries. If a fire extinguisher fails, the results can be disastrous. It is simply not enough to know how to operate them correctly, they must be inspected regularly and kept in good working order.
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