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Fire Extinguisher Advice

Fire Extinguisher Advice

Our information section is designed to help you make an informed choice when selecting a fire extinguisher. We have called upon the expertise of our network of BAFE registered extinguisher engineers, and a customer service team with a combined experience of over 40 years to create this guide.

Our objective is to enable you to purchase from us with complete confidence after reading through this guide. However, if you would like to discuss your specific needs, please feel free to contact us on 0800 612 4829, or via e-mail at

The information below will guide you through purchasing your extinguishers, and also offers general advice on the science of fire and firefighting for those looking to supplement their fire safety knowledge.

Selecting and Maintaining Extinguishers

The Science of Fire

Section 1 - What type of extinguisher do I need?

The type of extinguishers needed to protect any premises depends on the hazards present. General office environments can often be covered by either a mixture of CO2 and Foam extinguishers, by multi-purpose foam extinguishers such as the P50 Service-Free Extinguishers, or a new generation of Water Mist Extinguishers.

If you are unsure about the type of extinguishers needed, best practice is to have a site survey carried out by one of our qualified engineers who will be able to appraise any units currently on-site and make recommendations for further or alternate units if necessary. We strive to provide the best value possible to our customers, and you can rest assured that we will never oversell.

If you are replacing extinguishers like-for-like, please be aware that recent changes to official recommendations (BS5306-8: 2012) now advise against the use of powder extinguishers within enclosed areas (i.e. indoors). If you have powder units on site, it is still common practice to have these maintained until the end of their lifestrong, but once expired, they should be replaced with an alternative.

Below is a table identifying the different types of extinguishers available:

Fire Extinguisher Class of Fire Description
Water Fire Extinguisher WATER FIRE EXTINGUISHERS are especially designed for tackling Class A fires (wood, paper, straw, textiles, coal etc.).
(Dry) Water Mist Extinguishers A broad-spectrum fire extinguisher for tackling all common fires. Fights A, B, C and F class fires (although not officially rated for C Class) and is safe for use on live 230V electrical applications, as the water is de-ionised and does not carry current. It has been tested to be safe up to 1000V at 1m distance.
CO2 Fire Extinguisher CARBON DIOXIDE FIRE EXTINGUISHERS are suitable for electrical hazards and have been tested on B class fires. CO2 is harmless to electrical equipment and as such is ideal for modern offices and electronic risks as they do not leave a deposit. However, CO2 extinguishers are not good on general fires and while they are classified as suitable for B class fires, they are actually not that well suited for liquid fires, as the gas jet can carry burning liquid and therefore spread the fire and the hot liquids can re-ignite after the CO2 gas has drifted off.
Powder Fire Extinguisher POWDER FIRE EXTINGUISHERS are capable of tackling multiple classes of fire but are not generally deemed suitable for use indoors, as they affect visibility once deployed and cause problems through inhalation. They are the main type of extinguisher formally rated for tackling flammable gas risks, such as burning methane, propane, hydrogen, natural gas etc.
Wet Chemical Fire Extinguishers WET CHEMICAL FIRE EXTINGUISHERS are designed for tackling fat and 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).
Dry Chemical Powder Fire Extinguishers DRY CHEMICAL FIRE EXTINGUISHERS, also known as Class D extinguishers, are designed to tackle a unique industrial hazard. Fires involving burning metals such as aluminium, lithium, magnesium, potassium, sodium and their alloys require these specialist extinguishers to interrupt the chemical reaction and extinguish the fire.

Section 2 - How many fire extinguishers do I need?

Once you have identified the type of extinguishers needed, the next question is naturally:- how many do the premises need? For commercial or public areas, there are some basic rules of thumb to keep in mind. The relevant British Standard (BS5306-8: 2012) states that there must be a minimum of two A rated extinguishers, meeting a combined rating of 26A per floor for any storey less than or equal to 400m2. For floor areas over 400m2 this ratio must be maintained and can be calculated by multiplying the floor area in square metres by 0.065, i.e. 600x0.065= 39A.

In addition to these calculations, care must be taken to ensure that the extinguishers are within reasonable distance of any prospective operators, with a maximum travel distance of 30m specified. If this travel distance is likely to be exceeded, this requirement supercedes the area calculations, and extra units should be installed.

In its simplest terms, this means for small or medium sized areas two extinguishers, either water of foam, of 3Ltr size or larger will often suffice to adhere to the guidelines. All extinguishers sold by Actfire of 3Ltr or larger have a minimum 13A rating, meaning two of these units will help you meet the recommended level of coverage.

It is also necessary to account for potential fires involving electrical equipment. The most common way of protecting against this is to install CO2 extinguishers. These are often sighted next to the A rated extinguishers to create a single fire point, however it is often advisable to place a unit close by to any electrical equipment that could potentially be involved in a fire.

If you are unsure about the type or amount of extinguishers needed, best practice is to have a site survey carried out by a qualified engineer who will be able to advise if you are currently protected in accordance with the specifications of the British Standard. To arrange a site survey, please contact us on with details of your premises size and location.

We believe in providing the best possible value to our customers, therefore none of our engineers work on a commission basis and they will never try to upsell.

Section 3 - Where and how should I install fire extinguishers?

Best practice is to wall mount fire extinguishers wherever possible. All extinguishers provided by Actfire are supplied with the appropriate wall mounting bracket. As a general rule, extinguishers should be hung with the handle approximately 1m from the ground, with a corresponding identification sign mounted just above each unit.

Where it is not possible to wall mount an extinguisher, it is recommended to make use of a fire extinguisher stand. These are available as single stands for individual extinguishers, or more commonly as double stands to accommodate a pair of extinguishers. An empty extinguisher stand found during an inspection marks clearly where a fire extinguisher has been moved.

Care should be taken to make sure that extinguishers are sited in a highly visible location, and it is common practice for this to be close to a room exit on an escape route. Being installed near an exit also stops anybody going into a room on fire to fetch an extinguisher.

When installing new extinguishers, it is important to have these commissioned by a competent person. Commissioning ensures that the extinguisher has not been damaged in transport and that the pins can be removed easily. This is a service we are happy to offer, even if you decide to carry out subsequent servicing in-house or yourself.

Section 4 - How do I maintain extinguishers?

After being commissioned, traditional fire extinguishers need to be serviced on an annual basis by a ‘competent person’ in accordance with BS5306:8 2012. A competent person is defined as an individual having completed the necessary training and with access to the relevant tools, equipment and information to carry out the appropriate maintenance procedure. There is also an expectation that this individual be experienced in the process of servicing extinguishers.

Annual servicing comprises of a visual inspection, weight check, and replacement of perishable parts such as o-rings, and tamper seals. The engineer should then sign a service label on each unit serviced, and leave a copy of a service report with the customer.

After five years, all traditional extinguishers bar CO2 units must have an extended service carried out which involves emptying and re-filling the cylinder in addition to the regular servicing process. This allows the inspection of the internal surfaces of the extinguisher and extends the unit’s lifestrong by a further five years. CO2 extinguishers have a ten year lifestrong due to the lack of possibility of corrosion within the cylinder. When extinguishers reach ten years of age, they will often be replaced rather than refilled or refurbished (CO2). These milestones are frequently referred to as the extinguisher having ‘expired’.

Our network of service engineers are all BAFE registered, and as such are regularly audited for performance levels and competence. You can rest assured that any servicing organised by Actfire will be carried out to the highest standard, at very reasonable prices and with no agenda to oversell.

Larger organisations often choose to manage their fire safety equipment in-house. To support this, we sell a complete range of tools and consumables to enable you to carry out servicing if this is likely to be more cost effective.

If you are interested in maintaining your fire extinguishers in-house, but don’t want to invest in tools or the formal training as an engineer, P50 Service-Free Fire Extinguishers offer fantastic value over their twenty year lifestrong.

If you or your client wish to change over to servicing-free extinguishers, Actfire will carry out the site survey, installation and commissioning and then hand over the responsibility for the annual visual inspection to in-house staff or other maintenance personnel after carrying out and recording a short training session.

Section 5 - 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:

  1. 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)
  2. When the wood reaches about 150 degrees Celsius, the heat decomposes some of the cellulose material that the wood comprises of.
  3. Some of the decomposed material is released as volatile gases. These gases are more commonly known as smoke.

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 lightbulb. 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 were 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 its 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.

Fire Kills

Between April 2013 and March 2014, 322 people died as a result of a fire, and a further 9,748 suffered injury. 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.

If you discover a fire in its very early stages and think that you can deal with it yourself, you must remember 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 in order to safely escape the building.
  • Never tackle a fire if it is starting to spread, has spread to other items in the room or if the room is filling with smoke. Around 60% of fire deaths are linked to 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.

Section 6 - How do fire extinguishers work?

Fire extinguishers are available in two varieties - stored pressure and cartridge operated. Actfire only sells stored pressure extinguishers, but also sells the CO2 cartridges necessary to recharge a cartridge operated unit as part of our extensive range of extinguisher spares

Stored pressure fire extinguishers are fully pressurised cylinders that contain both the extinguishing agent and a propellant in the form of compressed air or nitrogen for Water, Powder, AFF Foam and Wet Chemical extinguishers. Carbon Dioxide extinguishers are only available 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 gas. As this happens the extinguishing agent is carried out of the canister and passes down the hose onto the fire.

Cartridge operated fire extinguishers are not pressurised when supplied. They contain a small CO2 cartridge that discharges into the cylinder when the extinguisher is activated and this effectively turns it into a stored pressure extinguisher. Cartridge operated units are particularly suitable for marine applications where there may not be access to a compressor unit for re-charging.

Regardless of the method of discharge or the type of extinguisher used, all extinguishers serve the common purpose of interrupting the chemical reaction behind the fire when correctly deployed.

Section 7 - What are the types of fire?

Class A Solid Wood, paper, textiles, straw, coal etc.
Class B Liquid Petrol, alcohol, oils, fats, paint, tar etc.
Class C Gas Propane, hydrogen, natural gas, methane etc.
Class D Metal Sodium, lithium, magnesium, potassium etc.
Class F Cooking Oil Cooking oils and grease
Electrical Electrical Not technically a class of fire. Used to reference fires involving electrical equipment.

Each extinguisher listing on Actfire clearly states the classes of fires capable of being fought by that extinguisher. If you are at all unsure about the suitability of a type of extinguisher, please contact us on 0800 612 4829, or via


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