Fire Extinguishers

Posted 05/02/2016

What are Fire Extinguishers?

A fire extinguisher is an active fire protection device that is used to control small fires in emergency situations. Not all fire extinguishers are the same, and the type of fire extinguisher you need depend on the possible fire hazards and different aspects of the particular building or area the fire extinguisher will be placed in. Fire extinguishers are NOT intended for use on a fire that is out of control, for example a fire that reaches the ceiling, which endangers those fighting the fire.

Why are Fire Extinguishers needed?

If you own a business then you are legally responsible for having the correct fire safety devices installed throughout the building. It is also your legal obligation to undertake a fire risk assessment to evaluate the risks of fire in your business premises as no premises is the same in this regard.

How many fire extinguishers you need throughout your business premises is not always the easiest thing to gauge, however there is a rough general rule to go by which is for every 200 metres squared you need one water based, water based with additive, or foam fire extinguisher. The water based extinguisher with additive is probably the best choice for most, however once again it is fully dependant on where it is situated within the building and what equipment, machinery or technology is in the room with it.

Fire extinguishers you have need at least a minimum fire rating of 13A, and this number will be stated near the neck of the bottle on the label. This rating affects the minimum amount of fire extinguishers per floor/per area. A rating of 21A on your fire extinguishers for example will translate to you needing less, because they are better equipped with more capacity to fight a fire.

The general formula for calculating this is floor space in metres squared multiplied by 0.065 then divided by the extinguisher rating then always round up. For example if your floor space was 1000 metres squared then you would do 1000 x 0.065 x 13 (if your extinguisher was rated 13A) which would come to 5, meaning you would need 5 13A extinguishers minimum for this floor space. This formula only applies to the type A fire extinguishers, and the number attached to the different types of fire extinguisher are not universal and the calculation for these is different.

How to choose the right fire extinguishers needed for YOU

There are a few different types of fire extinguishers out there, and each one of them has a particular class of fire that it is better at fighting than others. The types and uses go as follows:

Water - Fires involving organic solid materials like wood, cloth, coal, paper, plastics etc. Do not use on electrical fires or burning fat and oil fires. (Effective against class A only). Useful for some offices, schools, shops, pubs etc. generally places where there is no risk of a specialised fire of a class other than A. These are still the most commonly installed fire extinguishers around, but are also the least effective in general.

Water Spray (water with additive) - this has the same uses and weaknesses as the water jet extinguisher above, but is much more effective than traditional water jet extinguishers. (Effective against class A only). Useful for hotels, schools, churches and general offices etc. useful for places where risk of organic materials catching fire is the most likely fire class.

Water Mist (Dry Water Mist) - This is the first fire extinguisher on the list that is effective against more than one type of fire. This type of extinguisher can tackle organic solid material fires like explained above, flammable liquid fires (Class B), flammable gasses (Class C), and fat and oil fires (Class F). Models with dielectric test to 35K volts can be used on electrical fires up to 1000 volts because the mist is deionised, meaning it cannot conduct electricity, and this type of fire extinguisher does not form puddles. These are ideal for use in clean places, food production areas for example. There are all around very versatile so can be used in many different environments.

Dry Powder (Multi-Purpose) - these can be used on fires that are organic, flammable liquid fires, and flammable gas fires (so classes A, B, and C) and they are also safe for use on electrical fires although they do not penetrate into small places so fires within electrical appliances may not be extinguished by this type of fire extinguisher. Also this type of extinguisher does not cool fires very well, so extra precautionary action should be taken to ensure that the fire does not flare up again. Ideal for use in factories, workshops, garages etc. They are very versatile so you can use these in many places effectively.

Dry Powder (Special Powders) - these extinguishers are specialised for fires involving combustible metals such as lithium, magnesium, sodium and powdered aluminium (Class D). One thing to note is you should under no circumstances allow water to come in contact with the burning metals, and also the powder must be gently applied to be efficient.

Foam (AFFF) - Ideal for organic material fires and for flammable liquids (Classes A and B). Not safe for live electrical fires. These are ideal for use in larger kitchens, caravans, boats and smaller workshops.

Carbon Dioxide - this fire extinguisher is the most effective type for live electrical fires/equipment, although it can allow the re-ignition of hot plastics. It will also extinguish liquid fires (Class B). Has no post fire protection, hence the allowance for fire re-ignition. These are ideal for use in hospitals, factories, garages, large workshops etc.

Wet Chemical - these extinguishers are most effective at fighting fat and oil fires (Class F) and are also adept at fighting organic fires (Class A). Depending on your specific extinguisher, it may also be capable of fighting liquid fires (Class B) but you should always refer to your user manual for clarification, as these types are usually not recommended for this. These are usually ideal for use in kitchen and restaurants, where the risk of fat and oil fires is particularly high.

It is always best to seek professional guidance when buying fire extinguishers to install throughout a large business, or a business where there are unusual fire hazards or where chemicals are involved.

To view some more information on our wide product range of fire extinguisher equipment and read more about the products we offer visit our fire extinguisher equipment page.

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