Fire Advice
Find Your Engineer have many articles on advice for the types of Fire Extinguishers, Fire Extinguisher Servicing, Fire Safety, Fire Videos, Fire PDFs and more.
How Do Fire Extinguishers Work?
What Are The Rules / Regulations For Fire Extinguishers?
Where Do I Fix / Place My Fire Extinguishers?
Where Can I Find More Information About Fire Safety?
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 is as follows:
Wood is heated to a very high temperature. The heat can come from several different sources -- a match, focused light, friction, lightning, something else that is already burning (petrol etc) When the wood reaches about 150 degrees Celsius, the heat decomposes some of the cellulose material that the wood comprises of. Some of the decomposed material is released as volatile gases. These gases are more commonly known as smoke. Smoke is a compound of carbon, oxygen and oxygen.
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.
Fire Variables
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.
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Fire Kills
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.
Only tackle a fire in its very early stages.
Always put your own and other peoples safety first. Make sure you can escape if you need to and never let a fire block your exit.
Fire extinguishers are only for fighting a fire in its very early stages. Never tackle a fire if it is starting to spread of has spread to other items in the room or if the room is filling with smoke. Around 70% of fire deaths are caused by people being overcome by smoke and fumes.
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 immediately.
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.
Class ‘A’ fires are solid combustibles such as paper, plastic, textiles etc.
Class ‘B’ fires are those of liquid combustibles (petrol, diesel, paraffin).
Class ‘C’ fires are flammable gasses (methane, propane etc).
Class ‘D’ fires are combustible metals such as Potassium, Sodium etc.
There are also electrical fires – these are fires involving energised electrical equipment – If you remove the power to the electrical fire it becomes one of the other types of fire (Generally Class ‘A’).
Class ‘F’ fires are fires involving cooking oils and vegetable / animal fats.
Additionally, the majority of fire extinguishers have a numerical rating which is based on tests conducted by professional fire-fighters in test conditions, 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.
How do fire extinguishers work?
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.
What are the rules / regulations for fire extinguishers?
If your premises are single occupancy and not larger than 100sq Meters with an upper floor area of not more than 100 sq Meters then you will require a minimum fire test rating of 13A (which is the equivalent to 1 x 9L Water or greater than a 4Kg powder or greater than a 2 Litre Foam) plus you should also have a fire extinguisher to cover any specific risks (i.e. Co2 for electrical risks or possibility of liquid fires). If your building is larger than 400sq Meters then there should be a minimum of 2 fire extinguishers per floor and each floor should not have less than a fire test rating of 26 A (2 x 9 L Water or 2 x greater than a 4Kg powder or 2 x greater than a 2 Litre Foam) plus you should also have a fire extinguisher to cover any specific risks (i.e. Co2 for electrical risks or possibility of liquid fires). The formula is 0.065 x floor area (in Square meters) and that will give you the Class A fire test rating that you need as a minimum. If you have special circumstances, feel unsure or feel that you may be a high risk please contact your local fire services (Fire Officer)
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.
Office
The most common combination and safest cover is 1 x 9L Water or 6L 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 risks such as computers etc. Find a local or nationwide Fire Extinguisher Engineer with our free Directory:
Industrial Premises
The most common are Powder and Foam extinguishers coupled with Co2 for any electrical risk. The Powder covers all risks and especially fires which react with water or foam (electrical). 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. Find a local or nationwide Fire Extinguisher Engineer with our free Directory:
Industrial Kitchens
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. Find a local or nationwide Fire Extinguisher Engineer with our free Directory:
Residential
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. Find a local or nationwide Fire Extinguisher Engineer with our free Directory:
Vehicles
A 1kg or 2 Kg powder extinguisher should always be situated near the front seats. Find a local or nationwide Fire Extinguisher Engineer with our free Directory:
Requirement for main fire extinguishers
If a transport unit is not carrying dangerous goods in accordance with ADR 1.1.3.6, it has to be equipped with at least one portable fire extinguisher for the inflammability classes* A, B and C, with a minimum capacity of 2kg dry powder (or an equivalent capacity for any other suitable extinguishing agent) suitable for fighting a fire in the engine or cab of the transport unit [ADR 8.1.4.1(a). If the transport unit is carrying dangerous goods in accordance with ADR
1.1.3.6, it need be equipped only with a single portable fire extinguisher for the inflammability classes* A, B and C, with a minimum capacity of 2kg dry powder (or an equivalent capacity for any other suitable extinguishing agent) [ADR 8.1.4.2]. The additional fire extinguisher requirements (para 4.) does not apply.
If the vehicle is equipped with a fixed fire extinguisher, automatic or easily brought into action for fighting a fire in the engine, the portable extinguisher
need not be suitable for fighting a fire in the engine [ADR 8.1.4.3 para. 2]. The capacity of the fire extinguisher(s) required under ADR 8.1.4.1(a) may be
deducted from the minimum total capacity of the additional fire extinguishers required under 8.1.4.1(b) below [ADR 8.1.4.1(c)].
Requirements for additional fire extinguishers
These are set out in ADR 8.1.4.1(b): For transport units with a maximum permissible mass of up to and including 3.5 tonnes one or more portable fire extinguishers for the inflammability classes* A, B and C with a minimum total capacity of 4 kg dry powder (or an equivalent capacity for any other suitable extinguishing agent).
2 for transport units with a maximum permissible mass of more than 3.5 tonnes up to and including 7.5 tonnes one or more portable fire extinguishers for the inflammability classes* A, B and C, with a minimum total capacity of 8 kg dry powder (or an equivalent capacity for any other suitable extinguishing agent), of which at least one shall have a minimum capacity of 6 kg for transport units with a permissible maximum mass of > 7.5 tonnes one or more 12kg (or equivalent rating for suitable extinguishing agents) dry powder fire extinguisher for the inflammability classes* A, B and C suitable for fighting a fire in the engine or cab of the vehicle – at least one shall have a minimum capacity of 6kg. The requirements for additional fire extinguishers do not apply to transport units carrying dangerous substances of Class 6.2 [ADR 8.5 S3].
Further requirements relating to fire extinguishers these are set out in ADR 8.1.4.3 - 8.1.4.5: The extinguishing agent has to be suitable for use on a vehicle and has to comply with the relevant requirements of BS EN 3 Portable fire extinguishers, Parts 1 to 6 (BS EN 3-1:1996, BS EN 3-2:1996, BS EN 3-
3:1994, BS EN 3-4:1996, BS EN 3-5:1996, and BS EN 3-6:1995) [ADR8.1.4.3, para. 1]**;
The extinguishing agent must not be liable to release toxic gases— (a) into the driver’s cab; or (b) when under the influence of the heat of a fire.
[ADR 8.1.4.3, para. 2];The portable fire extinguishers have to be fitted with a seal verifying that they have not been used. They also have to bear a mark of compliance with a standard** recognized by a competent authority and an inscription at least indicating the date (month, year) of the next recurrent inspection or of the maximum permissible period of use, as applicable. [ADR 8.1.4.4,paras. 1, 2];
The fire extinguishers must be periodically inspected in accordance with authorized national standards** in order to guarantee their functional safety. [ADR 8.1.4.4, para. 3]; The fire extinguishers have to be installed on the transport units in such a way that (i) the vehicle crew can get at them easily; and, (ii) their
operational safety is not affected by the weather. 3 Also, ADR 8.2.2.4.5 requires that, as a minimum, individual practical exercises accompanying theoretical training as part of the initial driver training programme must cover: first aid, fire-fighting, and what to do in case of an accident or incident; and,ADR 8.3.2 requires the vehicle crew to know how to use the fire-fighting appliances. Find a local or nationwide Fire Extinguisher Engineer with our free Directory:
4 British Standards
*BS EN:2 1992 Classification of fires (ISBN
Class A fires involving solid materials, usually of an organic nature, in which combustion normally takes places with the formation of glowing embers
Class B fires involving liquids or liquefiable solids
Class C fires involving gases
Class D fires involving metals
BS EN:3-1 1996 Part 1: Description, duration of operation, Class A and B fire test
BS EN:3-2 1996 Part 2: Tightness, dielectric test, tamping test, special provisions
BS EN:3-4 1996 Part 4: Charges, minimum required fire
BS EN:3-5 1996 Part 5: Specification and supplementary tests
BS EN:3-6 1996 Part 6: Provision for the attestation of conformity of portable fire extinguishers in accordance with EN 3 Part 1 to Part 5
Where to fix /place your extinguisher
Fix or place 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. Find a local or nationwide Fire Extinguisher Engineer with our free Directory:
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. Check that your maintenance / fire engineer are registered and have the right qualifications e.g. BAFE registered. People can help with the servicing by having the designated fire warden check the extinguishers on a monthly basis to check for any visible damage to the outer body. Find a local or nationwide Fire Extinguisher Engineer with our free Directory:
BAFE is a Government recognised national organisation. You can get details of approved products and advice from:
British Approvals for Fire Equipment,
48a Eden Street,
Kingston upon Thames,
Surrey, KT1 1EE
Where can I find more information on fire safety?
You may want to try these websites for more info on fire and Safety:
www.ifeda.org - The Independent Fire Engineering And Distribution Agent.
www.BAFE.org.uk - British Approved Fire Equipment.
www.thefpa.co.uk - The Fire Protection Association.
www.hse.gov.uk - The Health And Safety Executive.
Visit our Links page for more information. To find a local or nationwide Fire extinguisher Engineer search our Fire Search section.
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