Firefighting is the act of extinguishing destructive fires. A firefighter fights these fires to prevent destruction of life, property and the environment. Firefighting is a highly technical profession that requires training and education in order to become proficient.


Types of Fires According to their Causes.

Before starting to fight the fire, it is important to know the size and type of the fire that you are going to put off. The kind of firefighting material you are going to use will also depend on the type of fire in question. Fires are classified based on the type of burning materials.

1. Class A fires

These are the fires in which the burning materials are ordinary combustible materials such as paper, wood, cardboard, coal, rubber, clothing, furniture and most plastics. Water is the best extinguisher for these fires. However, any other type of extinguisher, except carbon dioxide, may be used.

2. Class B fires

These fires involve flammable liquids such as petrol, kerosene, oil, alcohol, ether, vanishes, etc. For small fires, a fire blanket or sand may be used. If the fire is large, use foam, dry powder or carbon dioxide extinguisher. Water should not be used on class B fires because the burning material, being lighter than water, will just float and spread the fire further.

3. Class C fires

The burning material involves flammable gases e.g. hydrogen, acetylene, coal gas, butane, methane, propane, etc. The best extinguishers to use in fighting against these fires are foam, dry powder or carbon dioxide extinguishers. It is important to turn off the gas supply, and spray water on the gas tank to cool it down.

4. Class D fires

The burning material is a metal. Alkali metals such as sodium or potassium may catch fire when they come in contact with water and oxygen. At high temperatures, many metals react with oxygen vigorously. Fires that involve burning metals should not be extinguished by water. This is because the burning metal can react with water to give hydrogen (another potential fuel). The appropriate extinguisher to use is foam or dry powder extinguisher.

5. Class E fires

These fires involve electrical equipment such as appliances, wiring, circuit breakers and outlets. You may use carbon dioxide or dry powder extinguisher to put off these fires. Never use water as it can conduct electricity and give an electric shock. Also remember to switch off power from the mains.

6. Class F fires

The burning material is cooking oil or fat. A cooking oil fire in the kitchen can be extinguished by covering the pan with a fire blanket or damp cloth. Foam, dry powder or carbon dioxide extinguishers also work by cutting off the air supply to the fire. For large fires, wet chemical extinguishers are recommended.

Different Types of Fire Extinguishers used to Extinguish Different Types of Fire.

Before choosing the best fire extinguishers for fighting different types of fires it is crucial to identify the type of burning materials first, and hence the type of fire such as:

Class A: Solids such as paper, wood, clothing, rubber, etc
Class B: Flammable liquids such as paraffin, petrol, oil, spirit, alcohol, etc.
Class C: Flammable gases such as propane, butane, methane, hydrogen, etc
Class D: Metals such as aluminium, magnesium, titanium, etc
Class E: Fires involving electrical equipment such as appliances, circuit breakers and                          outlets, etc.

Types of fire extinguisher to use for each type of fire.



Water extinguisher

This is the cheapest and most widely used fire extinguisher. It is used for class A fires. It is not suitable for class B (liquid) fires, or where electricity is involved.

Foam extinguisher

This is more expensive than water extinguisher, but more versatile. It is used for classes A and B fires. Foam spray extinguishers are not recommended for fires involving electricity, but are safer than water if mistakenly sprayed onto live electrical apparatus.

Dry powder extinguisher

This is often termed as “multi-purpose” extinguisher, as it can be used on classes A, B and C fires. It is the best for liquid fires (class B). It will also efficiently extinguish class C (gas) fires. However, take care because it can be dangerous to extinguish a gas fire without first isolating the gas supply. 

Special powders are available for class D fires. When powder-type extinguishers are used indoors, the powder can obscure vision or damage goods and machinery. It is also very messy.

Carbon dioxide extinguisher

Carbon dioxide is ideal for fires involving electrical apparatus (class E). It will also extinguish class B (liquid) fires. However, the extinguisher has no post-fire security and the fire could reignite.

Wet chemical extinguisher

This is a special extinguisher for class F fires. The extinguisher contains potassium salts. The salts  not  only  help  to  cool  down  the  flames  but  also  form  a  „saponification‟  blanket  that effectively smothers the flames with thick, soapy foam.

Specialist powder extinguisher

This is a specialist fire extinguisher for use on class D fires (fires on combustible metals such as sodium, potassium, magnesium, lithium, titanium, manganese and aluminium), especially in the form of powder or turnings.

The Components Needed to Start a Fire

To extinguish fire, it is necessary to remove one or more of the three components of combustion. Any fire needs a fuel, oxygen (air) and heat to keep it going. Remove any one of them and the fire will go out. These components are as shown in the fire triangle below.

A fire will continue or start to burn if these components are present:

(i) Fuel: This refers to any combustible material be it solid, liquid or gaseous material provided it can catch fire and burn. You can stop fire by removing the combustible material from the path of fire.

(ii) Oxygen (air): Oxygen supports combustion. A fuel will only burn if there is sufficient supply of oxygen. You can extinguish fire by displacing, or taking away oxygen supply from the fire or by blocking the gas supply to the fire.

(iii) Heat: The temperature should be at the kindling point of that fuel or above it. Every fuel has its own kindling point. Below the kindling point, the fuel will not catch fire. You can put out fire by lowering the temperature below the kindling point of a particular fuel. Water may be used to cool down the fuel. The vapourization of water absorbs the heat; it cools the smoke, air, walls, objects etc, which could be used as further fuel.

Fire Extinguishers According to the Chemicals they Contain

Fire extinguishers are classified according to the type of chemicals they contain

1. Liquid carbon dioxide extinguisher

This extinguisher contains liquid carbon dioxide. The liquid is contained in a metal container. When the safety pin is removed, carbon dioxide evaporates as solid "snow" (carbon dioxide sublimes). The snow settles on the fire and suffocates it.

2. Soda-acid extinguisher

This extinguisher has a metal case containing soda (aqueous sodium carbonate or sodium hydrogen carbonate). In the metal case there is a glass bottle containing a concentrated acid (sulphuric or hydrochloric acid). There is a knob attached to the top of a metal case. Hitting this knob breaks the acid bottle thus bringing the acid and the soda into contact. The two react to give carbon dioxide, e.g.

The gas forms bubbles with the solution, thereby forming foam which is forced out of a jet of the case. The foam is directed to the fire where it covers the burning liquid, excluding all air from reaching the fire.
Some extinguishers are made in such a way that turning them upside down brings the soda and acid into contact and the reaction proceeds as stated above.

3. Foam extinguishers

This is different from the soda–acid type in that it contains sodium hydrogen carbonate in the metal case, but instead of the concentrated acid, it contains aluminium sulphate and saponium in the glass bottle. On mixing the three components, carbon dioxide gas is produced. The gas is ejected out as foam. The foam here lasts longer than the foam in the soda–acid extinguisher. The foam so produced also keeps air away from the burning material.

4. Dry chemical extinguisher

This extinguisher uses powdered sodium hydrogen carbonate and a nitrogen gas kept at high pressure. When the gas cartridge is broken using the top cap, the carbon dioxide under pressure propels the powder. The powder forms a layer over the burning material to keep air away.

Table below summarizes the types of fire extinguishers, indicating the chemicals they contain and the classes of fire they are suitable or unsuitable for.

Table: Types fire extinguishers and the chemical composition of their extinguishing agents


Precautions on using fire extinguishers

The following are some safety precautions you have to keep in mind when using fire extinguishers:

1. Keep a reasonable distance from the fire as it may suddenly change direction.
2. Never use a portable extinguisher on people, instead use a fire blanket.
3. Do not test a portable extinguisher to see if it works. It may leak and later fail to work during an emergency.
4. Do not return a used portable extinguisher to the wall. Make sure it is recharged first.
5. When a fire gets out of control, notify the nearest fire brigade.