Everything You Need to Know About Fire Extinguishers

Posted in Fire Extinguishers Fire Safety Equipment on 25 April 2016

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Fire extinguishers are an essential piece of fire safety equipment every premises is required to have. In order to ensure you have the correct fire extinguishers for your building, it is important to know the different options available, and which you are most likely to need.

Fire Extinguisher Classifications

A fire extinguisher is classified depending on the type of fire it is designed to put out ‐ fires
are categorised by classes.

  • Class A Extinguisher ‐ These extinguishers are suited for use on freely burning carbonaceous materials such as wood, paper and fabrics.
  • Class B Extinguisher ‐ For use on flammable liquid fires, such as oil, petrol and diesel
  • Electrical Extinguisher ‐ Meant for use on electrical fires. Can also be used on flammable liquids
  • Class C Extinguisher ‐ For use on Gaseous fires such as propane and butane.
  • Class D Extinguisher ‐ A specialist extinguisher for use on combustible metals such as Potassium, Sodium and Magnesium.
  • Class F Extinguisher – A specialist extinguisher for Deep Fat Fryers which use cooking oils.

Multi-Class Ratings

For added convenience, many extinguishers that are currently available can be used on multiple fire types, so will be marked with more than one classification.

How Fire Extinguishers Work

Fire extinguishers operate by affecting what is known as “the Fire Triangle” – the term used to describe the three essential components required for a fire to exist, these are FUEL, HEAT and OXYGEN.

4 Types of Extinguishers

Different extinguishers remove at least one of these three components, thus extinguishing the fire:

1. Dry Powder

This type of extinguisher is usually rated for multiple purpose use (Class A, Class B, Class C and electrical fires), although their use indoors is not recommended.

These contain a powder based extinguishing agent, this smothers the fire removing oxygen and alters its chemical composition.

2. Water

Suitable only for use on Class A fires (freely burning carbonaceous materials such as wood, paper and fabrics).

These extinguishers contain water (and sometimes a special additive) and these cause rapid cooling, reducing heat from the fire.

3. Foam

Suitable for use on Class A and Class B fires (freely burning carbonaceous materials such as wood, paper and fabrics and flammable liquids).

These extinguishers are water based with a special additive and these cause rapid cooling, reducing heat from the fire, but the special foam additive also removes oxygen too.

4. Carbon Dioxide

Primarily designed for use on electrical fires, but suitable for use on flammable liquids fires, these displace oxygen, reducing levels to an extent where a flame cannot be sustained.

How to use a Fire Extinguisher

Modern extinguishers operate on a simple “seize and squeeze” method of operation. An easy way to remember this is with the acronym PASS which describes the four stages:

1. Pull

Pull out the safety pin from the operating levers/handle that prevents the extinguisher being accidently discharged. There may also be a tamper evident seal fitted to the extinguisher; these are designed to break very easily as the safety pin is removed.

2. Aim

Aim the nozzle/discharge horn of the fire extinguisher at the base of the fire.

3. Squeeze

Completely squeeze the operating levers/handle in order to discharge the extinguisher, ensuring you are the appropriate distance from the fire.

4. Sweep

Sweep the nozzle/discharge horn back and forth at the base of the fire to ensure it is extinguished. Be sure to keep going until the extinguisher is empty to avoid reignition.

*For Class F extinguishers (cooking oils), completely discharge the extinguisher into the deep fat fryer from a minimum 1m distance away, with the lance held directly above the burning oil.


Fire Action supply a comprehensive range of fire extinguishers, as well as a professional installation and maintenance service for all customers. We also provide a range of fire safety equipment, fire risk assessments and training.

For more information, feel free to contact us today and we’ll be happy to help you.

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