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Different Types Of Fire Extinguisher
This information is designed to help you make the right choice when purchasing a fire extinguisher. Please read the information we have provided to determine the right fire extinguisher for your requirement. We are available on should you wish to discuss your requirement in more detail.
Our fire extinguisher advice is split into the following key sections:
Section 1 - What is a fire?
Section 2 - What are the types of fire?
Section 3 - What are the types of fire extinguisher?
Section 4 - How do fire extinguishers work?
Section 5 - What are the regulations for fire extinguishers?
Section 6 - How Many Fire Extinguishers do I need ?
Section 7 - Where and how should we install our fire extinguishers ?
Section 1 - What is a Fire ?
As a general rule, fire is caused by a chemical reaction between oxygen in the atmosphere and some sort of fuel (wood or petrol for example). Of course, wood and petrol don't spontaneously combust just because they're surrounded by oxygen. For the reaction to happen, you have to heat the fuel to a sufficient temperature, this is known as the ignition temperature.
The sequence of events in a typical wood fire are as follows:
• The actual burning of wood then happens in two separate reactions: When the volatile gases are hot enough (about 260 degrees Celsius for wood), the compound molecules break apart, and the atoms recombine with the oxygen to form water, carbon dioxide and other products. In other words, they burn. A side effect of these chemical reactions is a lot of heat. The fact that the chemical reactions in a fire generate a lot of new heat is what sustains the fire. Many fuels burn in one step. Petrol is a good example. Heat vaporizes petrol and it all burns as a volatile gas. Humans have also learned how to meter out the fuel and control a fire, for example; a candle is a tool for slowly vaporizing and burning wax.
• As they heat up, the rising carbon atoms (as well as atoms of other material) emit light. This effect is called incandescence, and it is the same kind of chemical reaction that creates light in a light bulb. It is what causes the visible flame. Flame colour varies depending on what temperature the fire is burning at. Colour variation within in a flame is caused by uneven temperature. Typically, the hottest part of a flame -- the base -- glows blue, and the cooler parts at the top glow orange or yellow. In addition to emitting light, the rising carbon particles often collect on surrounding surfaces as soot.
In the previous section, we saw that fire is the result of a chemical reaction between two gases, oxygen and a fuel gas. The fuel gas is created by heat. In other words, with heat providing the necessary energy, atoms in one gaseous compound break their bonds with each other and recombine with available oxygen atoms in the air to form new compounds plus lots more heat.
There are only a few compounds that will readily break apart and recombine in this way -- the various atoms must be attracted to one another in the right manner. For example, when you boil water, it takes the gaseous form of steam, but this gas doesn't react with oxygen in the air. There isn't a strong enough attraction between the two hydrogen atoms and one oxygen atom in a water molecule and the two oxygen atoms in an oxygen molecule, so the water compound doesn't break apart and recombine.
The most flammable compounds contain carbon and hydrogen, which recombine with oxygen relatively easily to form carbon dioxide, water and other gases.
Different fuels ignite at different temperatures. It takes a certain amount of heat energy to change any particular material into a gas, and even more heat energy to trigger the reaction with oxygen. The necessary heat level varies depending on the nature of the molecules that make up the fuel. A fuel's piloted ignition temperature is the heat level required to form a gas that will ignite when exposed to a spark.At the unpiloted ignition temperature, which is much higher, the fuel ignites without a spark.
The fuel's size and surface area also affect how easily it will catch fire. A larger fuel, such as a railway sleeper, can absorb a lot of heat, so it takes a lot more energy to raise any particular piece to the ignition temperature. If you where to reduce the railway sleeper to sawdust it would burn far more easily as it takes much less heat energy due to the fact that a higher ratio of it’s mass is exposed to oxygen.
The heat produced by a fuel depends on how much energy the gases release in the combustion reaction and how quickly the fuel burns. Both factors depend largely on the fuel's composition. Some compounds react with oxygen in such a way that there is a lot of "extra heat energy" left over. Others emit a smaller amount of energy. Similarly, the fuel's reaction with oxygen may happen slowly, or it may happen more quickly.
In this way, fires from different fuels are like different species of animal -- they all behave a little differently. Experts can often figure out how a fire started by observing how it affected the surrounding areas. A fire from a fast-burning fuel that produces a lot of heat will inflict a different sort of damage than a slow-burning, low-heat fire.
Each year nearly 700 people die from fire in their own home. A further 14,000 are injured. The best way to avoid this danger is to prevent fire from starting in the first place. But what should you do if you discover a fire in your home? You must get everyone out as quickly as possible and call the fire brigade.
However if you discover a fire in its very early stages and think that you can deal with it yourself. The first thing that you should remember is that fire spreads very quickly. Even a small, contained fire can quickly spread, producing smoke and fumes, which can kill in seconds. If in doubt do not tackle the fire, no matter how small.
You can put yourself at risk by fighting the fire. If in doubt get out, get the brigade out, stay out.
Before you tackle a fire...
Many people put out small fires in their homes quite safely. Sadly, however, some people die or are injured by tackling a fire which is beyond their capabilities. Here is a simple home fire code to help you decide whether to put out or get out.
If you cannot put out the fire or if the extinguisher becomes empty, get out and get everyone else out of the building immediately, closing all doors behind you as you go. Then telephone the fire brigade.
Section 2 - What are the types of fire ? back to top
There are six different types or classes of fire, each of which has extinguishers to tackle the specific types of fire. Newer fire extinguishers use a picture/labelling system to designate which types of fires they are to be used on.
Additionally, the majority of fire extinguishers have a numerical rating which is based on tests conducted by professional fire-fighters that are designed to determine the extinguishing potential for each size and type of extinguisher.
In the instance of class ‘A’ fires, the numerical value is the size of fire in cubic metres that the extinguisher can put out.
For class ‘B’ fires the numerical value represents the amount of litres of flammable liquid that can be extinguished.
Class ‘C’ fires have no numerical value as flammable gas is very difficult to measure in cubic metres - it depends on the ratio of gas to air there is in the local atmosphere.
Class ‘D’ fires have a numerical value, this represents size of fire in cubic metres that the extinguisher can put out.
‘E’ Class fires have no numerical value – please remember once the source of the electricity is shut down, the electrical fire will revert to a different class.
The numerical value in ‘F’ class fires is the same as in ‘B’ class fires – it represents the amount of litres of flammable liquid (cooking oils etc) that can be extinguished.
Section 3 - What are the types of fire extinguisher? back to top
|Fire Extinguishers||Class Of Fire||Description|
|Water Fire Extinguisher||WATER FIRE EXTINGUISHERS are especially designed for tackling Class A fires (wood, paper, straw, textiles, coal etc.).|
|Foam Fire Extinguisher||FOAM FIRE EXTINGUISHERS are ideally suited where both class A & B fire risks exist. Aqueous Film Forming Foam or AFFF is particularly suited to fight liquid spill fires such as petrol, oil, fats, paints etc. and works by forming a film on the liquid to extinguish the fire. This extinguisher has also passed the electrical conductivity test at 35kv.|
|CO2 Fire Extinguisher||
CARBON DIOXIDE FIRE EXTINGUISHERS are suitable for class B risks involving flammable liquids and especially for electrical hazards. These extinguishers have been a natural replacement for Halon. CO2 is harmless to electrical equipment and as such is ideal for modern offices, electronic risks, and fires caused by the combustion of liquids such as: oils, fats, solvents, etc.
|Powder Fire Extinguisher||POWDER FIRE EXTINGUISHERS are especially suited to mixed fire risk environments and a good all round extinguisher. They are also suitable for flammable liquid risk, such as methane, propane, hydrogen, natural gas etc.|
|Wet Chemical Fire Extinguishers||WET CHEMICAL FIRE EXTINGUISHERS are especially designed for tackling cooking oil / deep fat fryer (Class F) fires, but also have an effective capability for extinguishing Class A fires (wood, paper, straw, textiles, coal etc.). This extinguisher has also passed the electrical conductivity test at 35kv.|
Section 4 - How do fire extinguishers work? back to top
Fire extinguishers come in 2 varieties – Stored pressure and cartridge operated.
Stored pressure fire extinguishers are fully pressurised cylinders that contain both the extinguishing substance AND propellant (in the form of compressed air or Nitrogen for Water, Powder, AFF Foam and wet chemical extinguishers). Carbon Dioxide extinguishers are only sold in stored pressure canisters as the CO2 itself is stored under pressure (so it is actually a liquid) and therefore the expanding gas propels itself from the extinguisher. As the handle is pressed down, the valve is opened and releases the compressed air, as this happens the extinguishant is carried out of the canister and passed down the hose onto the fire.
Cartridge operated fire extinguishers are not pressurised – they have a small CO2 cartridge that discharges into the cylinder when the extinguisher is activated and effectively turns it into a stored pressure extinguisher.
Section 5 - What are the regulations for fire extinguishers? back to top
Where to fix your fire extinguisher
Fix an extinguisher where you can reach it quickly. The best place is on an escape route, that is near an outside door, or on the route from the living areas to an outside door, or adjacent to a specific risk. It should be properly fixed to the wall at a height where it can be reached. Keep it out of the reach of children.
Fire extinguishers should be fixed where they can be easily seen. Fixing them inside cupboards or behind doors will only waste valuable time if a fire breaks out. Do not place them over cookers or heaters or in places of extreme temperatures.
Fire Extinguisher Maintenance
The manufacturers instructions will tell you what you need to do to keep your extinguisher in good working order. After an extinguisher has been used, even if only partially, it must be recharged according to the manufacturers instructions.
The extinguisher should be serviced annually.
You should always use an accredited company for the supply and maintenance of your fire equipment or you risk your insurance cover being invalid. More information on this topic coming soon!
Section 6 - How Many Fire Extinguishers Do I Require ? back to top
The amount required is calculated by the size of your premises and the risk involved.
Guidelines when calculating (Please note that these are guidelines and are based on low risk premises):
Fire Extinguisher - Technical Calculations
Please note that fire test ratings on fire extinguishers vary from manufacturer to manufacturer, so please do not assume that any 2 fire extinguishers are the same. The fire extinguishers mentioned above are based on the products supplied by EFireSafety Limited.
Disclaimer: EFireSafety Limited intends the above mentioned as guidelines and this should not be taken as law. The above mentioned is taken from the relevant British Standards. EFireSafety Limited will not be held responsible for any misinterpretations or where a company uses the above and does not conform to the standard. EFireSafety Limited advises that where possible companies are unsure that they seek the advice from the local fire brigade (Fire Officer).
Fire Extinguishers - Example Situations
The most common combination and safest cover is 1 x 9L Water or 9L Foam and 1 x 2Kg Co2. The water or foam covers all Flammable solids like paper, carpet, curtains etc and the Co2 covers all electrical risk such as computers etc
The most common are Powder and Foam extinguishers coupled with Co2 for electrical risk. The Powder covers all risks and especially fires which react with water or foam, Foam is ideal for flammable liquid fires. Please note that this is for general circumstances, it may vary depending on what machinery is used and what is being stored.
This will depend mainly on the methods of cooking, but the most common are Co2 for electrical fires, Dry Powder for Flammable Gas (Gas Ovens) and Wet Chemical for Deep Fat Fires. There should also be a fire blanket installed.
A 1Kg powder or 2 Kg powder should be sufficient to cover all normal risks and this should be supplemented with a fire blanket. This should always be situated in the kitchen
A 1kg or 2 Kg powder extinguisher should always be situated near the front seats.
Section 7 - Where and how should we install our fire extinguishers ? back to top
The extinguishers should be mounted on the wall (our fire extinguishers come with a ready to mount bracket) or on a stand with the handle approximately 1m from the ground; they should have the corresponding Identification Sign mounted above. The fire extinguishers should always be situated in a conspicuous position where they can readily be seen by persons following the escape routes. They should be located near room exits, in corridors, on stairway lobbies and landings on each floor.
If you are unsure or require further advice please feel free to contact us on and one of our qualified engineers will be able to offer you advice.