FIRE EXTINGUISHER TYPE AND USES
No single fire extinguisher can be used to tackle every fire, and because each type of fire extinguisher has different categories of fire on which it is effective, Fire extinguisher types and uses selection can be a minefield. The good news is that portable fire extinguishers are effective and are saving lives. According to a survey from companies in the four main trade associations in the UK fire sector, the number of fires being success
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 fire classes involving different substances:
- Class A fire caused by combustible carbon-based solids such as paper, wood or textiles
- Class B fire caused by flammable liquids eg paraffin, petrol, diesel or oil (but not cooking oil)
- Class C fire caused by flammable gases, eg butane, propane or methane
- Class D fire caused by 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 fire caused by 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 colour for foam, blue for dry powder, yellow coded extinguishers are used for wet chemical, green for clean agent and black for CO2 extinguishers.
Fire extinguisher types and uses
Water fire extinguishers (red label)
Water extinguishers are only used for Class A fires. Therefore, red coded extinguishers can be used to tackle fires caused by ignited paper, wood, straw, coal, rubber, solid plastics and soft furnishings. Water fire extinguishers work by spraying water from the spray nozzle, which helps to cover larger surface area. 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. This extinguishes the flames, absorbing heat from burning objects.
They 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
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 water mist extinguishers 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.
Water spray fire extinguishers
Available in three and six litres, water spray fire extinguishers are suitable to fires involving organic solid materials such as wood, cloth, paper, plastics or coal. Use on burning fat or oil or on electrical appliances is a big no-no.
Use involves pointing the jet at the base of the flames and moving it constantly and steadily across the fire until extinguished.
Example of a CO2 fire extinguisher and water-based fire extinguisher in an office
A jet nozzle is eschewed in favour of a spray nozzle, which creates a fine spray courtesy of the higher pressure. Hitting a broader surface area this extracts heat more rapidly. Surfactants can be added to help the water penetrate further into burning material.
Foam extinguishers (cream label)
The foam smothers the fire in solids and liquids (Class A and B), but not in burning fats or cooking oils (Class F), so foam fire extinguishers are used on burning liquids such as petrol, paint or turpentine. A foam extinguisher can also 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 label)
Powder fire extinguishers are used for fighting burning solids, liquids and gases (Class A, B and C fires). Specialist 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 reigniting. 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 label)
These contain only pressurised carbon dioxide gas and therefore leave no residue. Carbon Dioxide (CO2) extinguishers are used 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 label)
These are the only extinguishers apart from water mist suitable for Class F oil 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 fire extinguisher types to use
- Class A fire extinguisher – water, water mist, foam, dry powder, wet chemical
- Class B fire extinguisher – water mist, foam, dry powder, CO2, some wet chemical
- Class C fire extinguisher – water mist, dry powder
- Class D fire extinguisher – specialist dry powder
- Electrical fire extinguisher – CO2
- Class F fire extinguisher – water mist, wet chemical.
Fire extinguishers for electrical fires
In 2017, it was reported that nearly to deal with electrical fires – a survey revealed. In addition, electrical fires have become more common causes of fire due to a greater reliance on electrical products and batteries. In 2021, electricity was the according to a fire industry survey, so it’s important to know which extinguishant should be used.
For electrical fires, CO2 fire extinguishers should be used. By displacing the oxygen in the air, they help to suffocate the fire and prevent it from spreading, while leaving no residue, making them harmless to electrical equipment. They are often found in data/computer server rooms, offices, kitchens and construction sites for this very reason.
Dry powder extinguishers, which have a blue label, are said to be OK to use on electrical fires involving equipment under 1000v, though CO2 extinguishers are still advised.
When an electrical fire is taking place, respondents should not use water-based, foam, or wet chemical extinguishers.
How to use a fire extinguisher
Fire extinguishers should ideally only be used by someone who has been trained to do so – and the following text does not count as training. Moreover, a fire extinguisher should only be activated once the fire alarm has been triggered and you have identified a safe evacuation route. Evacuate the building immediately if you still feel unsure about using a fire extinguisher or if doing so is clearly the safest option.
Nevertheless, the following technique can serve as a refresher for those who have undertaken training or if someone without training ever needs to use one in order to improve the chances that everyone escapes unharmed.
The following four-step technique can be memorised more easily with the acronym PASS, to help you use a fire extinguisher:
- Pull: Pull the pin to break the tamper seal.
- Aim: Aim low, pointing the nozzle or hose at the base of the fire. (Do not touch the horn on a CO2 extinguisher since it becomes very cold and can damage skin.
- Squeeze: Squeeze the handle to release the extinguishing agent.
- Sweep: Sweep from side to side at the base of the fire – the fuel source – until the fire is extinguished.
Key on using a fire extinguisher include:
- Never use a fire extinguisher on flames from a fire involving escaping gas
- Only tackle a fire in its earliest stages
- Do not move forward unless it is safe, and you should always remain at least one metre from the fire
- Do not use more than one fire extinguisher to tackle a fire
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 for Class B fires, which are spilled flammable liquids. They must not be used with water on burning fat or oil or on electrical appliances. However, they’re sometimes left empty or misused and have a limited effect as they can’t 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 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
Automatic fire extinguishers are 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.
Class A – Suitable for paper, wood & textiles.
Type of fire extinguisher – Water, Foam, Dry Powder, Wet Chemical
Class B – Suitable for flammable liquids.
Type of fire extinguisher – Foam, Dry Powder, Carbon Dioxide (CO2)
Class C – Suitable for flammable gasses.
Type of fire extinguisher – Dry Powder
Class F – Suitable for cooking oil and fat.
Type of fire extinguisher – Wet Chemical
Electrical Risk – Suitable for electrical equipment.
Type of fire extinguisher – Dry Powder, Carbon Dioxide (CO2)
Fire Extinguisher Colour Coding or Colour Bands
Current fire extinguishers in the UK are subject to strict standards and that includes their colour coding or colour bands.
Fire extinguishers that meet the BS EN3 standard are manufactured with a red body and have a zone band of a second colour, covering up to 10% of the surface, that indicate the extinguisher’s contents. Each type of fire extinguisher has a particular zone of colour making it easier for the user to identify the contents of the fire extinguisher.
Older fire extinguishers that pre-dated the current standard are still found. These extinguishers were in colours other than the now predominantly red colour required to conform to BS EN3 and may still be legal. However, if they need to be replaced because they are unserviceable or damaged, the new extinguisher needs to comply with the new requirements if it is to meet the BS EN3 standard.
Typical colour zones of current fire extinguishers in the UK and the key features of each are: