Understanding the Different Types and Uses of Fire Extinguishers

September 22, 2020
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There are different types of fire extinguishers because there are various types of fires. Each extinguisher is suitable for fighting certain types, and it’s important for you to know the differences if it’s your job to fight fires at work. Being able to immediately distinguish which extinguisher you need in an emergency could make a lifesaving difference.

Throughout this article, we will explain the different classes of fires, the symbols that identify these, and the different types of extinguishers and their uses.

What Are the Different Classes of Fires?

Fires must be fought carefully depending on the materials involved. That is why they have been classified in 6 different categories:

  • Class A – Fires that involve solid flammables and dusts, such as wood, plastics, paper and cardboard, fabric and textiles, and dusts such as grain dust and flour.
  • Class B – Fires that involve flammable liquids, such as gasoline, petroleum oil, paint, or diesel.
  • Class C – Fires that involve flammable gases, such as propane, butane, or methane.
  • Class D – Fires that involve combustible metals including metal swarf, such as magnesium, lithium, sodium, potassium, titanium, or aluminium.
  • Electrical fires. Although it is not recognised as a separate class of fire in Europe, electrical fires that involve live equipment and electrical sources are also a type you should bear in mind. Think of it as an informal Class E.
  • Class F – Fires that involve hot cooking oils and fats, such as vegetable oil, sunflower oil, olive oil, maize oil, lard, or butter (typically those used for deep-fat fryers).
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All extinguishers will have one or more of the following classes symbols, to indicate which class of fire they are suitable for.

Classes of fires

Each type of fire extinguisher contains different materials that make them suitable for fighting certain types of fires, and is designed to safely and effectively discharge its contents. The correct one must be used for the right class of fire, otherwise they may prove ineffective or in fact worsen the situation.

For example, using a water extinguisher on an electrical fire or a carbon dioxide one on a burning oil fire is extremely dangerous.

What Are the Different Types of Fire Extinguishers?

There are five main types of fire extinguishers:

  1. Water.
  2. Powder.
  3. Foam.
  4. Carbon Dioxide (CO2).
  5. Wet chemical.

Each type is easily identifiable by their names, colours, and sometimes their hoses. Depending on their size, some may not come with a flexible hose, such as smaller foam or aqua water spray extinguishers.

Types of fire extinguishers illustration

Let’s take a look at each type of fire extinguisher, their uses, and their risks below.

1. Water Extinguishers

There are two main types water extinguishers: standard water spray and dry water mist.

Standard water extinguishers

These will be solid red and will have the word ‘water’ or ‘aqua spray’ printed across them in a signal red band, often with a white border. They are your classic model: they dispense water at a high pressure to extinguish flames.

Water extinguishers are only suitable for class A fires, which means they can fight fires that involve wood, cardboard, paper, plastics, fabric and textiles, and other solid materials.

Aqua Spray Extinguisher

Warning: do not use water extinguishers on burning fat and oil fires and electrical appliances.

Water extinguishers can sometimes contain chemical additives that improve their effectiveness by up to 300%. The chemicals remove the water’s natural surface tension so that it soaks into burning materials more effectively when used.

Dry water mist extinguisher

These types of fire extinguishers will be solid red and will usually have the words ‘water mist’ printed within a white rectangle.

Dry water mist extinguishers are unique in that many of them can combat almost all types of fires, including class F fires that are usually difficult to attack. The extinguisher’s nozzle converts water into ‘dry’ microscopic particles, which are then drawn into the fire and simultaneously cool and suffocate it to extinguish the flames.

They are also effective for fire-fighting because they form a safety barrier between the user and the fire – which repels some of the heat – and do not leave hard-to-clean residue behind.

Warning: Although they are not currently classified as suitable for fighting class B (liquids) and C (gases) fires, dry water mist extinguishers have been identified by fireservice.co.uk as effective against them.

Other types will be better suited for fighting electrical fires, but dry mist extinguishers have usually had dielectrical tests carried out on them, which means that if they are accidentally used on electrical fires, they will not pose as significant a hazard as normal water extinguishers.

2. Powder Extinguishers

There are three types of powder extinguisher: ABC powder, M28 powder, and L2 powder.

ABC powder extinguisher

These types of extinguishers will say ‘powder’ in white text over a blue rectangle, and underneath the rectangle will be written ‘ABC powder’.

As their name suggests, these are designed to combat class A, B, and C fires – those involving solids, liquids, and gases. The powder acts as a thermal blast that cools the flames so burning cannot continue. Due to their non-conductive nature, they are also suitable for fighting electrical fires. However, they do not effectively penetrate the spaces in equipment easily, so the fire could still re-ignite.

Warning: do not use on domestic chip or fat pan fires (class F).

The downside to ABC powder extinguishers is that they pose a danger of inhalation when used in confined spaces, so they must not be used in them. They also leave residue behind that is difficult to clean up and causes damage to soft furnishings, carpets, and electrical equipment. This is why it’s advised you use a different type of extinguisher for fires involving electronics, such as in an office with computers.

M28 and L2 powder extinguishers

These types of extinguishers are best identified by their unique hose, though they will also say ‘powder’ in white text in a signal violet rectangle. They are often referred to as special powder. Do not confuse these with the ABC powder extinguishers, as they are not designed for class A, B, or C fires. They will state below the rectangle whether they are M28 or L2.

M28 and L2 are unique extinguishers in that they are designed for tackling Class D fires – those involving combustible metals including swarf or powder, which are often produced in engineering factories. Metals includes lithium, magnesium, sodium, or aluminium, for example.

M28 and L2 Powder Extinguisher

The extinguisher has a low velocity applicator to ensure that the M28 or L2 powder is applied gently and efficiently to burning metal and to prevent the swarf from spreading. When sprayed, it forms a ‘crust’, which insulates the metal. This prevents the fire from spreading to other flammable materials and smothers the fire to prevent oxygen from reacting with the metal again.

L2 is suitable for all types of metal fires, whereas M28 cannot be used on lithium.

Warning: do not use on any other fire type, especially live electrical fires. Also, bear in mind that water should not be allowed to come in to contact with burning metal.

3. Foam Extinguishers

Foam extinguishers are identifiable by the word ‘foam’ printed within a cream rectangle on their bodies. They are primarily water based but contain a foaming agent, which has rapid flame knock-down and a blanketing effect. It smothers the flames and seals vapours so that re-ignition cannot occur.

They are suitable for fighting class A and B fires.

When used against class A fires, the user can simply point and spray. However, when used against class B fires – those with flammable liquids – they should not be sprayed directly into the liquid. This could cause the fire to be pushed and spread to surrounding areas. The best method of application is to spray the foam nearby so that it can build up and flow across it.

Foam Extinguisher

Warning: these should not be used on any other fire classes, especially electrical fires or chip or fat pan fires. Many foam extinguishers will have had dielectrical tests performed on them, so foam is less hazardous than water if it is accidentally sprayed on live electrical equipment. However, they should still not be used to fight electric fires as they are not specifically designed for them.

4. Carbon Dioxide (CO2) Extinguishers

These types of extinguishers can be identified by the text ‘carbon dioxide’ or ‘CO2‘ printed in white on a black rectangle. They also have a distinct type of hose.

Carbon dioxide extinguishers are used for combating class B and electrical fires – they suffocate the fire by displacing oxygen in the air. Because they do not leave any substances behind and so minimise damage done to equipment, unlike other extinguishers, they are particularly useful for offices and workshops where electrical fires may occur.

Carbon Dioxide CO2 Extinguisher

Warning: they must not be used on hot cooking oil and fat (class F) fires. The strong jet from the extinguisher would push the burning oils or fats and spread the fire to surrounding areas. Also bear in mind that while carbon dioxide is effective at smothering fires, once the gas has floated away, the fire may reignite if the source has not been removed.

Furthermore: you must not hold the horn, base, or pipework on a CO2 extinguisher while operating it. The gas becomes extremely cold during its discharge and this could damage your hands.

5. Wet Chemical Extinguishers

These types of fire extinguishers are identifiable by the words ‘wet chemical’ printed across a yellow rectangle. It also has an extended hose that you can hold and point, which is useful when fighting fires on a kitchen top.

Wet chemical extinguishers are designed for combating fires that involve class F fires. They are effective because they are capable of stopping fires that are of an extremely high temperature, particularly cooking oils and fats. They also discharge gently, stopping the burning oils and fats from being pushed and splashing to surrounding areas or even the user.

Wet Chemical Extinguisher

The chemicals contained within the canister dispels the flames, cools the burning oil, and produces a soap-like solution that seals the surface and prevents re-ignition of the fire.

The best method of application is to spray in slow circular motions. The user should empty the entire contents onto the oils or fats. Otherwise, the fire may re-ignite.

Warning: wet chemical extinguishers are usually not recommended for class B fires – those involving liquids. Also, although they are capable of combating class A fires, they are not as effective as other extinguishers at doing so.

Fire extinguishers are an important addition to fire safety measures, as they can help to stop small fires. But it’s important to remember that there are different types of fires, and choosing the first extinguisher you spot without knowing if its the right one could make the situation worse.

The information throughout this article has provided some key guidance on the different types of extinguishers and their uses, but keep in mind that you also need practical training to learn how to safely handle extinguishers.

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