Types of Fire Extinguishers
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Different types of Fire Extinguisher:
Water Extinguishers Overview;
There are four different types of water extinguishers: water jet, water spray, water with additives and water mist or fog.
Water extinguishers are the easiest variety of fire extinguisher to maintain and they are the least hazardous as they only contain water.
Chemical additives can increase the effectiveness of a water fire extinguisher by up to 300% and this reduces the size and weight of extinguisher required – these are a little more expensive.
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.
Label Colour: Signal Red
Water extinguishers are only suitable for Class A fires – Combustible materials. Fire fuelled by solid materials such as paper, wood, fabrics, textiles, cardboard, straw, coal, rubber, solid plastics and soft furnishings. They are the simplest, most common, and least expensive type of extinguisher.
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.
How water extinguishers work:
The water has a cooling effect on the fuel (reduces the pyrolysis rate of the fuel), causing it to burn much more slowly until the flames are eventually extinguished. They cool the fire by soaking it and the materials with water. This extinguishes the flames, absorbing heat from burning objects.
Water Spray Extinguishers (Water with additive):
Water spray extinguishers come equipped with a spray nozzle instead of a jet nozzle which means the water is able to cover a much greater surface area quickly in order to put out the fire more rapidly.
Water extinguishers with additives are water extinguishers with foaming chemicals added. The water loses its natural surface tension meaning that it can soak into the burning materials more effectively. Adding the chemicals to the water means that a smaller extinguisher can produce the same fire rating as a larger, water only, extinguisher.
Label Colour: Signal Red
Fires involving organic solid materials such as wood, cloth, paper, plastics, coal, etc. These offer significantly improved firefighting capability compared to traditional jet type water fire extinguishers. Available in 3 and 6 litres.
Do not use on burning fat or oil or on electrical appliances.
How water spray extinguishers work:
Water has a great cooling effect on the fuel’s surface and thereby reduces the pyrolysis rate of the fuel. Instead of a jet nozzle, a spray nozzle is used, with a higher pressure, which creates a very fine spray of water droplets, each droplet is surrounded by air which is non-conductive. This allows for a given quantity of water to have a considerable increase in the surface area presented to the fire. This makes extinguishing more efficient by more rapid extraction of heat, the formation of steam, etc. They can also contain surfactants which help the water penetrate deep into the burning material which increases the effectiveness of the extinguisher. Most water spray fire extinguishers carry a 35 kV dielectric test approval which means they have been tested on a 35,000 Volt electrical source at one metre.
Water Mist Extinguishers:
Water mist extinguishers have a different type of nozzle again which releases extremely small microscopic water particles. This extinguisher nozzle releases microparticles that ‘suffocate’ the fire and also keep the person using the extinguisher safe by creating a wall of mist which helps in reducing the feeling of heat.
Label Colour: Signal Red on a White Background
The first broad spectrum extinguisher to tackle A, B, C rated risks as well as fats and deep fat fryers (Class F). Models filled with de-ionised water tested with a dielectric test to 35k Volts can be safely used on electrical fires (up to 1000 Volt) if a safety distance of 1m is adhered to, as their mist (de-ionised water) does not conduct electricity and the extinguisher does not normally form puddles, which could conduct electricity.
Water mist extinguishers are safe for discharge on all fire classifications bar Class D fires.
How water mist extinguishers work:
In water mist, or fog, extinguishers, water is turned into microscopic particles in the nozzle. The droplets are much smaller than those from the water spray extinguisher. The smaller the droplet, the larger the surface area in relation to its size, the quicker the droplet evaporates which absorbs the heat energy faster. The water mist is drawn to the fire where it cools and suffocates the fire. The mist also forms a safety barrier between user and fire, which keeps some of the heat back.
Foam extinguishers are the most common type of fire extinguisher for Class B fires, but also work on Class A fires.
Label Colour: Cream
They are most suited to extinguishing liquid fires such as petrol, diesel or paint and are more versatile than water jet extinguishers because they can also be used various organic materials including wood, coal, textiles, fabrics, cardboard and paper. Safe on fires caused by electricity if tested to 35kV (dielectric test) and a 1m safety distance is adhered to.
Do not use on chip or fat pan fires.
How foam extinguishers work:
They are mainly water-based and foam smothers the fire in solids and liquids (Class A and B), but not in burning fats or cooking oils (Class F).
The foam extinguishes liquid fires by creating a cooling effect on the fuel and sealing the surface of the liquid, preventing flammable vapour reaching the air and starving the fire of fuel thus breaking the interaction between the flames and the fuel surface. They are not suitable for use on free-flowing liquid fires.
Dry Powder Extinguishers:
Standard dry powder extinguishers are also called ‘ABC’ extinguishers because they are suitable for fighting burning solids, liquids and gases (Class A, B and C fires). ABC powder extinguishers can also be used on some electrical fires.
Label Colour: Blue
Organic materials such as paper and cardboard, fabrics and textiles, wood and coal…Plus: Flammable liquids, like paint and petrol… Plus: Flammable gases, like liquid petroleum gas (LPG) and acetylene… Plus: Fires involving electrical equipment up to 1000v
Can be used on fires involving organic solids, liquids such as grease, fats, oil, paint, petrol, etc but not on chip or fat pan fires. Can also be used on gas fires.
Disadvantages are that the powder does not soak into smouldering materials in deep-seated fires such as upholstery or bedding 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. Due to this, and the potential for powder to impair vision, powder extinguishers are no longer recommended for use within enclosed spaces.
The powder damages electronics, soft furnishings, machinery, etc, and needs a lot of cleaning up after use.
Do not use for: fires involving cooking oil, fires involving electrical equipment over 1000v or in enclosed spaces, such as offices or residential properties
Safe on live electrical equipment, although does not penetrate the spaces in equipment easily and the fire may re-ignite. This type of extinguisher does not cool the fire very well and care should be taken that the fire does not flare up again.
How dry powder extinguishers work:
Dry powder extinguishers smother fires by forming a barrier between the fuel and the source of oxygen and stops it from spreading.
Specialist dry powder extinguishers are only used on flammable metals,
Specialist dry powder extinguishers are designed to tackle type D fires and work in the same way as standard dry powder extinguishers but are for use with flammable metals only, such as lithium, titanium, aluminium and magnesium. There are 2 types of specialist dry powder extinguishers – ‘L2’ which only tackles lithium fires, and ‘M28’, for all other flammable metal fires.
CO2 extinguishers contain only pressurised carbon dioxide gas and are ideal for modern offices or places with a lot of electrical equipment such as server rooms. The CO2 is harmless to electrical equipment which does not cause damage to the electrical items or cause the system to short circuit and does not leave any residue, unlike a foam extinguisher. They can also be used on Class B fires, those involving flammable liquids such as paint, paraffin or petrol.
Label Colour: Black
Live electrical equipment, although it allows re-ignition of hot plastics. Now mainly used on large computer servers, although care has to be taken not to asphyxiate people when using the extinguisher in small server rooms. Flammable liquids, like paint and petrol.
This type of extinguisher does not cool the fire very well and you need to ensure that the fire does not start up again.
Do not use on chip or fat pan fires, as it can carry burning fat out of the container.
Fumes from CO2 extinguishers can asphyxiate if used in confined spaces: ventilate the area as soon as the fire has been controlled.
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.
The strong jet from the extinguisher can spread burning combustible materials like paper, wood or textiles.
How CO2 fire extinguishers work:
Carbon dioxide extinguishers work by suffocating the fire. Carbon dioxide displaces oxygen the fire needs to burn. However, once discharged, the CO2 will dissipate quickly and allow access for oxygen again, which can re-ignite the fire.
Wet Chemical Extinguishers:
Wet chemical extinguishers are suitable for use on Class F fires involving cooking oils and fats and are mainly used in kitchens with deep fat fryers. They are extremely effective when used correctly. Although they are primarily designed for use on Class F fires, cooking oils and deep fat fryers. They can also be used on Class A fires (wood, paper and fabrics) and Class B fires (flammable liquids).
These are the only extinguishers apart from water mist suitable for Class F fires.
Label Colour: Yellow
Cooking oil/fat fires such as lard, olive oil, sunflower oil, maize oil and butter and organic materials such as paper and cardboard, fabrics and textiles, wood and coal
Do not use for: flammable liquid or gas fires, electrical fires, flammable metals
How Wet Chemical fire extinguishers work:
Most Class F extinguishers contain a solution of potassium acetate, sometimes with some potassium citrate or potassium bicarbonate. The extinguishers spray the agent out as a fine mist. The mist acts to cool the flame front, while the potassium salts saponify (form a soap-like solution on the surface of the burning cooking oil), preventing oxygen from fuelling the fire any further and sealing the surface and preventing re-ignition. This solution thus provides a similar blanketing effect to a foam extinguisher, but with a greater cooling effect. The saponification only works on animal fats and vegetable oils, so most Class F extinguishers cannot be used for Class B fires. The misting not only cools the flames but also helps to prevent splashing the blazing oil.
Fire blankets are primarily for use on small hot oil fires such as frying pans or small deep fat fryers if a good seal can be made. They can also be used for wrapping around a person whose clothing has caught 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.
Fire blankets conforming to British Standard BS EN 1869: 2019 are suitable for use in the home. BS 7944: 1999 is the specification for specialist heavy-duty industrial use. Fire blankets should generally be disposed of after use.
Label Colour: Signal Red
Small pan fires where oil or fat has caught fire and clothing fires.
If the blanket does not completely cover the fire, it will not be able to extinguish the fire.
While kitemarked fire blankets have been successfully tested on deep fat fryers, modern frying fats are difficult to extinguish with a fire blanket. Therefore, wet chemical fire extinguishers are recommended for deep fat fryers.
How fire blankets work:
They work by smothering the fire, preventing access to the oxygen fuelling it and extinguishing it.
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. Their use is advisable but is not a legal requirement in ordinary cars.
Please note that this article provides basic easy-to-understand guidance of fire safety provisions and the key fire safety information required to comply with legislation. Our articles are reviewed regularly. However, any changes made to standards or legislation following the review date will not have been considered. We aim to assist you to understand the fire-related terms within your Fire Risk Assessment. It does not provide detailed technical guidance on all fire safety provisions, and you might require further advice or need to consult the full standards and legislation.
Fire Risk Consultancy Services have the knowledge and experience to assist your business to comply with all legal requirements surrounding Fire Safety including the legislation regarding Fire Alarms. Be sure to read our accompanying guides: Guide to Classes of Fire in the UK from A to F, How Many Fire Extinguishers Do I Need?, Siting of Fire Extinguishers, Chrome Fire Extinguishers, P50 Fire Extinguishers AND Fire Alarm System Types, Emergency Lighting, Fire Door Regulations, Fire Safety Signs, also published on this site.
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