Fire Extinguishers

Fire extinguisher types: How to choose the right class

Journalist, Cherry Park

Author Bio ▼

Cherry Park is an experienced freelance journalist and reporter who specializes in features, news, and news analysis, in print and online. She has written extensively in the areas of health and safety, fire safety, employment, HR, recruitment, rewards, pay and benefits, market research, environment, and metallurgy, and she also conducts research.
April 26, 2017

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Choosing the correct type of fire extinguisher for the relevant class of potential fire could literally be the difference between life and death.

No single extinguisher can be used to tackle every fire, and because each type of fire extinguisher has different classes of fire on which it is effective, selection can be a minefield.

Further reading: Fire extinguishers: your legal obligations and How to use a fire extinguisher safely and effectively

The first step is to look at what materials are present in the area to be protected from fire. These can be divided into six categories of fire involving different substances:

  • Class A, combustible carbon-based solids eg paper, wood or textiles
  • Class B, flammable liquids eg paraffin, petrol, diesel or oil (but not cooking oil)
  • Class C, flammable gases, eg butane, propane or methane
  • Class D, burning metals, eg aluminium, lithium or magnesium
  • Fires caused by electrical equipment (indicated by an electric spark symbol and not the letter E)
  • Class F, fats and cooking oils.

In the UK, portable fire extinguishers must conform to BS EN3 Standard, which specifies that their body is coloured red. A small coloured band indicates the type of fire extinguisher – red for water, white and red for water mist, cream for foam, blue for dry powder, yellow for wet chemical, green for clean agent and black for CO2 extinguishers.

The prices of all extinguishers vary widely according to supplier, so purchasers are advised to shop around. The future cost of servicing will also need to be taken into consideration. Some firms charge for installation and commissioning, but they should be supplied with a 5-year warranty and mounting brackets included. Approximate prices given below include VAT.

Water extinguishers (red)

Water extinguishers are only suitable for Class A fires consisting of paper, wood, straw, coal, rubber, solid plastics and soft furnishings. They are the simplest, most common, and least expensive type of extinguisher, costing from around £25 for 3- or 6-litre, to £35 for 9-litre ordinary models, and £50 for freeze-protected extinguishers. Some have an additive to make the water more effective and reduce the required size and weight of the extinguisher – these are a little more expensive.

Water extinguishers are the easiest to maintain variety and the least hazardous, since they only contain water. They cool the fire by soaking it and the materials with water, extinguishing the flames and absorbing heat from the burning objects, and are often found in shops, offices, retail premises, schools, hotels, warehouses and domestic premises. They may have spray or jet nozzles and are usually able to put out a fire completely.  A drawback is that they cannot be used on burning fat or oil (Class F), burning metals (Class D), burning liquids (Class B) or electrical appliance fires.

Water mist extinguishers (red on white)

The newest type of extinguisher, these very powerful, but smaller, devices exude an ultra-fine mist of microscopic ‘dry’ demineralised water particles. They are safe and effective to use on Class A, B, C and F fires, making it unnecessary to supply more than one type of extinguisher in most premises. Some are also suitable for use on electrical fires on equipment up to 1,000 Volts, such as computers and printers.

They work by cooling the fire and reducing the oxygen supply. These devices are likely to replace wet chemical extinguishers for the extinction of deep fat fryer fires, and leave no residue or collateral damage. Like water extinguishers, they are recyclable and do not contain any chemicals. However, they cannot be used on Class D fires (metals).

Water mist extinguishers are more expensive than water extinguishers, costing from around £50 for 1 litre to £100 for 6 litres.

Foam extinguishers (cream)

The foam smothers the fire in solids and liquids (Class A and B), but not in burning fats or cooking oils (Class F). They can be used on some electrical fires if they have been tested and if fired from 1 metre away. However, they leave a residue that has to be cleaned up, and they are more expensive than water extinguishers, at around £25 for 1 litre and £55 for 9 litres.

Dry powder extinguishers (blue)

These are suitable for fighting burning solids, liquids and gases (Class A, B and C fires). Special powder extinguishers are designed to tackle type D fires involving combustible metals such as lithium, magnesium, or aluminium.

They work by the powder forming a crust which smothers the fire and stops it from spreading.

Disadvantages are that the powder does not soak into materials and does not have an effective cooling effect on the fire, which can result in the fire re-igniting. The powder is hazardous if inhaled, so they should be used in well-ventilated areas and are not suitable for offices and domestic premises. The powder damages soft furnishings, machinery, etc, and needs a lot of cleaning up after use. They cannot be used on chip pan fires (Class F).

They are generally inexpensive and powerful and come in 1, 2, 4, 6 and 9-kg sizes. A 1kg model can cost as little as £15, while 9kg will cost around £35.

CO2 extinguishers (black)

These contain only pressurised carbon dioxide gas and therefore leave no residue. They are suitable for use on fires involving burning liquids (Class B), and electrical fires, such as of large computer equipment, so are practical in offices. CO2 works by suffocating the fire and does not cause damage to the electrical items or cause the system to short circuit.

However, CO2 extinguishers get very cold during discharge, and those that are not fitted with double-lined, frost-free swivel horns may cause fingers to freeze to the horn during deployment. They can asphyxiate in confined spaces, and they are not suitable for deep fat fryers, as the strong jet from the extinguisher can carry the burning fat out of the fryer. Fires can quickly re-ignite once the CO2 has dissipated into the atmosphere, so they do not offer post-fire security.

CO2 extinguishers are quite expensive. A 2kg model costs around £33, while a 5kg model, suitable for server rooms and factories, costs from £65.

Wet chemical extinguishers (yellow)

These are the only extinguishers apart from water mist suitable for Class F fires (fats and cooking oils) and are mainly used in kitchens with deep fat fryers. They can also be used on Class A and some can be used on Class B fires. They consist of a pressurised solution of alkali salts in water, which, when operated, creates a fine mist, cooling the flames and preventing splashing. More expensive than some others, they cost around £35 for 2-litre, £70 for 3-litre and £110 for 6-litre sizes.

Which types of extinguisher to use

Class A fires – water, water mist, foam, dry powder, wet chemical

Class B – water mist, foam, dry powder, CO2, some wet chemical

Class C – water mist, dry powder

Class D – specialist dry powder

Electrical – water mist, foam, CO2

Class F – water mist, wet chemical.

Fire blankets, hoses and buckets

These methods of fire extinction are useful additions to extinguishers.

Fire buckets can be used filled with water on Class A fires, or with sand to use as an absorbing agent on spilled flammable liquids (Class B). They must not be used with water on burning fat or oil or on electrical appliances. However, they are sometimes left empty or misused and have a limited effect as they cannot be used on large fires. Plastic fire buckets with lids cost around £15, while metal ones can be bought for around £23.

Fire hoses let out water at high pressure. They can be effective on Class A fires, but are very heavy. Prices of hose reels start at around £100 and vary widely depending on size and mounting.

Fire blankets are effective in smothering small, contained fires in kitchens or boats, if a good seal is made, and for wrapping round people whose clothing is on fire. Made of fibreglass, they can withstand temperatures of up to 500° C and are compact and portable. They don’t need any maintenance but can only be used once. They are cheap, and can be purchased for as little as £7 for a one-metre square blanket. Larger sizes cost around £15.

Automatic fire extinguishers

This type is designed to combat fires in transport, such as in the engine compartments of boats or large vehicles, or in industrial use, such as in generator or computer rooms. Advantages include easy recharging and lack of constant monitoring, and removal of the need for manual operation in unmanned areas.

These extinguishers are designed to spring into action when they detect heat. On the downside, their placing is crucial, since they could be set off erroneously when the ambient temperature reaches the trigger level.

Available as dry powder (blue) or clean, inert extinguishing gas, which replaces the now illegal halon, banned in the UK because of its effect on the ozone layer (green), they protect against Class A, B, C and electrical fires.

They cost from £30 to £85 for smaller models; complete systems can cost from £500 to £1,750.

Vehicle fire extinguishers

Generally containing dry powder for tackling Class A, B and C fires, their size should be selected according to the size and type of vehicle. They can be bought for around £11 for a 600g model to £70 for 12kg for larger vehicles. Their use is advisable, but is not a legal requirement in ordinary cars.

Fire extinguisher covers

Cost between £8-£25 depending on size and are used to protect extinguishers in harsh environments. Hose reel covers are also available.

Fire Extinguisher articles

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5 Comments on "Fire extinguisher types: How to choose the right class"

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Bernard Clyde
Guest

I appreciate you explaining the different classes of items as well as fire extinguishers, Cherry, and how both need to be considered before tackling a fire. It’s important people understand this so that they can adequately put a fire out before things get out of hand. Plus, I think it can instill a lot of confidence in individuals when a fire does happen which can help them to take action and fix the problem.

Violette Lebrac
Guest

Cherry, I didn’t know that water extinguishers are the easiest to maintain and the most likely to be found around in schools and shops. I am looking to get a fire extinguisher to put in my home in case of kitchen fires, and I want to find the kind that would be the most effective. A water extinguisher might not put out oil fires in the kitchen, so I’ll probably consult a professional to help me decide.

Alexandria Martinez
Guest

As my fiance and I looked into getting a fire extinguisher for our home, I was shocked to find out there are different kinds of extinguishers. We will be keeping it in our kitchen. This means we’ll need one that can put out grease fires. Thanks for the post! This was very helpful.

Adam Bannister
Admin

Glad we could be of help!

extintores secom
Guest

is there any difference between F and K class? De pends of the country or region?