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Fire extinguisher types – when and how they should be used

by | Apr 14, 2022 | Health and Safety

RealSense Learning take a look at the latest types of fire extinguishers, additional fire-fighting equipment and a best practice approach to fire safety in the workplace.

There are different types of fire extinguishers suitable for tackling different types of fire. It is important for your workforce to know what action to take in the event of a fire incident, be familiar with fire extinguishers, know when and how to operate them, if required to do so in the event of a fire.

Taking the right action quickly in the event of a fire incident or emergency situation can save time, save money and most importantly can save lives.

This resource explains the classification of fires, the symbols used to represent the different classes of fires, the different types of fire extinguishers and when and how to use them. 

Fire extinguisher types, when and how they should be used

Classes of fire

Fires are classified by the type of fuel involved. At the time of writing this article there are six classes of fire defined in the UK and Europe. The classification of fires is as follows.

  • Class A – Fires that involve solid flammable materials normally organic e.g. wood, paper, cardboard, coal, plastic etc. Also included are fabrics and textiles as well as dusts such e.g. grain and flour.
  • Class B – Fires that involve flammable liquids, such as petrol, diesel, oils, spirits, solvents and liquefiable solids, some forms of plastic, rubber, waxes etc.
  • Class C – Fires that involve flammable gases, such as acetylene, natural gas, hydrogen, liquefiable gases, propane, butane or methane etc.
  • Class D – Fires that involve combustible metals including aluminium magnesium, sodium which are typically machined or milled as well as potassium and titanium. Only specially trained personnel with specialist equipment should tackle such fires.
  • Electrical fires (Class E) Although not recognised in Europe as a separate class of fire, electrical fires involving live equipment and electrical sources are also a type of fire to consider. This is often informally categorised as Class E. Once the electrical item is removed the fire changes class.
  • Class F – Fires that involve cooking oils and fats used in kitchens. Examples of oils and fats include vegetable oil, sunflower oil, olive oil, lard and butter e.g. those commonly used in deep-fat fryers.

Colour coded fire extinguishers

All fire extinguishers are colour coded to help convey which can be used on each class of fire. Fire extinguishers provided on premises should be appropriate to the most likely classes of fire at that location.

It is important to understand that no single type of fire extinguisher is completely effective on every class of fire. When using a fire extinguisher (and indeed when procuring suitable fire extinguishers for the workplace) it is essential to carefully understand what class of fire they are to be used on.

Types of fire extinguisher with signage

Variations in fire extinguisher and classifications

It is important to note that there may be variations with manufacturer signage and instructions for fire extinguisher use, so please refer to the manufacturer guidelines before use, and or when procuring appropriate fire extinguishers for workplace premises.

Water Fire Extinguisher

Colour code / label

Red

Purpose

The water fire extinguisher is for use on fires involving organic solid materials such as wood, cloth, paper, plastics, coal etc.

Danger(s)

Do not use on burning fat or oil or on electrical appliances.

How to use

Direct the jet at the base of the flames and keep it moving across the area of the fire. Ensure that all areas of the fire are out.

How it works

Water has a significant cooling effect on the fuel’s surface and thereby reduces the pyrolysis rate of the fuel.

Water fire extinguisher sign
Water fire extinguisher

Water Spray Fire Extinguisher (Water with additive)

Colour code / label

Red on a white background

Purpose

The water spray fire extinguisher is for use on fires involving organic solid materials such as wood, cloth, paper, plastics, coal etc. These offer improved fire-fighting capability compared to traditional water fire extinguishers.

Danger(s)

Do not use on burning fat or oil or on electrical appliances.

How to use

Direct the jet at the base of the flames and keep it moving across the area of the fire. Ensure that all areas of the fire are out.

How it works

Water has a significant 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 fine spray. 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, 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.

Water mist fire extinguisher sign
Water mist fire extinguisher

Water Mist Fire Extinguisher (De-Ionised Water)

Colour code / label

Red on a white background

Purpose

The first broad spectrum fire extinguisher to tackle A, B, C rated risks as well as small amounts of burning fats. Models filled with de-ionised water and tested with 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. The water mist fire extinguishers also contain only de-ionised water which cannot carry any electric current.

Danger(s)

Do not use on deep fat fires or Grade D (burning metal swarf) fires.

How to use

Direct the nozzle at the base of the flames and keep it moving across the area of the fire. Ensure that all areas of the fire are out. The fire draws the microscopic water particles into the fire.

How it works

Water is turned into microscopic particles in the supersonic nozzle. 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.

Water mist fire extinguisher sign
Water mist fire extinguisher

Dry Powder Fire Extinguisher (Multi-Purpose)

Colour code / label

Blue (ABC Powder)

Purpose

The dry powder fire extinguisher is for use 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.

Danger(s)

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.

Smouldering material in deep seated fires such as upholstery or bedding can cause the fire to start up again.

Do not use on domestic chip or fat pan fires. There is also danger of inhalation if powder extinguishers are used within buildings. Due to this, and the potential for powder to impair vision, powder extinguishers are no longer recommended for use within enclosed spaces.

How to use

Direct the jet or discharge horn at the base of the flames and, with a rapid sweeping motion, drive the fire towards the far edge until all the flames are out. If the extinguisher has a hand control, wait until the air clears and if you can still see the flames, attack the fire again.

How it works

Similarly to almost all extinguishing agents, the powder acts as a thermal ballast making the flames too cool for the chemical reactions to continue. Some powders also provide a minor chemical inhibition, although this effect is relatively weak. These powders thus provide rapid knockdown of flame fronts, but may not keep the fire suppressed.

Powder fire extinguisher sign
Powder fire extinguisher

Dry powder Fire Extinguisher (Special Powders)

Colour code / label

Blue

Purpose

These specialist powder fire extinguishers are designed to tackle fires involving combustible metals such as lithium, magnesium, sodium or aluminium when in the form of swarf or powder. There are three special powders based on graphite, copper and sodium chloride.

Danger(s)

Do not allow water to come in contact with the burning metal and the powder must be gently applied. Sodium Chloride is not recommended for Lithium.

How to use

The lance enables the user to tackle fires at a safe distance. The low velocity applicator reduces the energy of the jet allowing the powder to gently smother the surface of the burning material thus avoiding scattering the high temperature particles and stimulating the formation of a crust. The method of application is completely different from a standard extinguisher and user training is required. They are not suitable for use on live electrical fires.

How it works

This powder fire extinguisher works by forming a crust which insulates the metal to prevent access to other combustible material nearby and smothering the fire to prevent oxygen from the atmosphere reacting with the metal

Foam Fire Extinguisher (AFFF)

Colour code / label

Cream

Purpose

The foam fire extinguisher is for use on fires involving solids and burning liquids, such as paint and petrol but not suitable for chip or fat pan fires. Safe on fires caused by electricity if tested to 35kV (dielectric test) and a 1m safety distance is adhered to.

Danger(s)

Do not use on chip or fat pan fires.

How to use

For fires involving solids, direct the jet at the base of the flames and keep it moving across the area of the fire. Ensure that all areas of the fire are out.

For fires involving liquids, do not aim the jet straight into the liquid. Where the liquid on fire is in a container, point the jet at the inside edge of the container or on a nearby surface above the burning liquid. Allow the foam to build up and flow across the liquid.

How it works

They are mainly water based, with a foaming agent so that the foam can float on top of the burning liquid and break the interaction between the flames and the fuel surface.

Foam spray fire extinguisher sign
Foam fire extinguisher

Carbon Dioxide Fire Extinguisher

Colour code / label

Black

Purpose

The carbon dioxide fire extinguisher is for use on fire involving live electrical equipment, although it allows re-ignition of hot plastics. Now mainly used on computer equipment e.g. server facilities, although care has to be taken in small server rooms as CO2 gas is poisonous at 4% and can kill at just 8% concentration.

Danger(s)

Do not use on chip or fat pan fires, as it can carry burning fat out of the container. This type of extinguisher does not cool the fire very well and you need to ensure that the fire does not start up again. Fumes from CO2 extinguishers can asphyxiate if used in confined spaces: ventilate the area as soon as the fire has been controlled. Only use CO2 extinguishers with frost-free horns, as the hand holding the horn can otherwise be frozen to the horn, as the gas gets very cold during the discharge. A relatively small increase in CO2 levels can overcome and potentially kill a user.

How to use

The discharge horn should be directed at the base of the flames and the jet kept moving across the area of the fire. Note: CO2 extinguishers only provide 6 to 10 seconds of fire fighting.

How it works

Carbon dioxide fire extinguishers work by suffocating the fire. Carbon dioxide displaces oxygen in the air. However, once discharged, the CO2 will dissipate quickly and allow access for oxygen again, which can re-ignite the fire.

Carbon dioxide CO2 fire extinguisher sign
Carbon dioxide co2 fire extinguisher

Wet Chemical Fire Extinguisher

Colour code / label

Yellow

Purpose

Wet chemical fire extinguishers are ideal for Class F fires, involving cooking oils and fats, such as lard, olive oil, sunflower oil, maize oil and butter.

Danger(s)

These extinguishers are usually not recommended for class B fires such as petrol so check manufacturer’s instructions for suitability of use.

How to use

Apply the wet chemical using the extended applicator in slow circular movements, which gives a gentle, yet highly effective application. Apply the fine spray onto the burning fat until the surface of the burning cooking oil changes into a soapy like substance which prevents re-ignition. The gentle application helps to prevent burning oil splashing out of the container. Make sure that you empty the entire content of the wet chemical extinguisher onto the oil/fat, as the fire can re-ignite otherwise.

How it works

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 the surface of the burning cooking oil, producing a layer of foam over the surface. 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 also helps to prevent splashing the blazing oil.

Wet chemical fire extinguisher sign
Wet Chemical Fire Extinguisher

Other fire fighting equipment

Fire Blanket

Fire blankets are made of fire-resistant materials and are useful for smothering small pan fires or for wrapping round a person whose clothing is on fire. Fire blankets conforming to British Standard BS EN 1869 : 1997 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.

Purpose

Fire blankets are for use on fire involving small pan fires where oil or fat has caught fire and clothing fires.

Danger(s)

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. We therefore recommend wet chemicals for deep fat fryers.

How to use

Place carefully over the fire. Keep your hands shielded from the fire. Do not waft the fire towards you.

How it works

Smothers the fire and prevents oxygen getting to the fire.

Fire Hose Reel

Purpose

Fire hose reels are used to provide a controlled supply of water to combat any potential fire risk involving combustible solids (Class A such as wood, cloth, paper, plastics, coal etc.) and require connection to a pressurised source of water either from the mains supply or a storage tank.

Danger(s)

Do not use on burning fat or oil or on electrical appliances before the electric supply has been isolated.

How to use

Point the jet at the base of the flames and keep it moving across the area of the fire. Ensure that all areas of the fire are out.

How it works

Water has a significant effect on cooling the fuel surfaces and thereby reducing the pyrolysis rate of the fuel.

Fire Buckets

A simple bucket of water can be used on Class A type of fires either to supplement a water extinguisher or as a first attack if an extinguisher is not immediately available.

A fire bucket can also be filled with dry sand and used as an absorbing agent or to dam a flow of flammable liquid. They do have serious disadvantages as they are often misused, left empty or allowed to be used as a refuse container.

Purpose

A fire bucket filled with water can be used on fires involving wood, cloth, paper, plastics and coal etc.

A fire bucket filled with sand can be used on fires involving spilled flammable liquids.

Danger(s)

Do not use on burning fat or oil or on electrical appliances before the electric supply has been isolated.

How to use

Throw at the base of the flames. Ensure that all areas of the fire are out.

How it works

Water has a great effect on cooling the fuel surfaces and thereby reducing the pyrolysis rate of the fuel.

Using a fire extinguisher

Remember you are not expected to fight fires unless you feel safe and confident to do so. If there are no fire exit routes available and the ONLY MEANS OF ESCAPE is obstructed by fire then you can consider using a fire extinguisher to aid your escape.

IMPORTANT

  • If Class C or D fires are considered to be a possibility in your workplace, then you should seek advice from a competent person e.g. qualified fire safety consultant, fire and rescue service.
  • It is not safe to fight fires involving aerosols with fire extinguishers.

Unlocking the trigger

Before a fire extinguisher can be used, you need to remove the locking mechanism, usually a pin or clip. This pin or clip is usually held in position by a plastic seal or disc that is designed to release easily to allow operation of the trigger. Locking mechanisms vary but the more common ones are shown here.

Unlocking fire extinguisher trigger

How to use a fire extinguisher with PASS – Pull, Aim, Squeeze and Sweep

Learning how to use a fire extinguisher should be part of an organisation’s fire safety training. An easy and memorable approach for remembering how to operate an extinguisher is by using the acronym P.A.S.S which stands for Pull, Aim, Squeeze and Sweep.

1. Pull: Pull the pin to break the seal and activate the extinguisher.

2. Aim: Aim low and point the hose at the base of the fire. Do not hold the horn on a CO2 extinguisher as it could damage your skin.

3. Squeeze: Squeeze the handle to release the extinguishing agent.

4. Sweep: Sweep the hose back and forth at the base of the fire until it is out.

IMPORTANT
All premises must have appropriate fire-fighting equipment

  • Indicated with appropriate signage
  • Easily accessible
  • Simple and easy to use

What you need to know about using a fire extinguisher

  • All staff should know how to use
  • Fire alarm should always be operated before attempting to tackle a fire
  • Make yourself aware of the location of fire extinguishers in the workplace
Using a fire extinguisher using the PASS approach

Fire safety training

Fire Safety Law

Firstly, it is a legal requirement that all employees undergo basic training at induction.

Secondly, refresher training should be given at regular intervals.

Thirdly and most importantly, the training must be carried out by a competent person. In other words, someone with suitable and sufficient skills and knowledge.

The Regulatory Reform (Fire Safety) Order 2005 states that employees should receive adequate fire safety training.

In conclusion, employers have a legal obligation to provide their staff with complete and relevant information concerning fire.

Fire safety training should cover four key areas:

  • Fire prevention, rules and regulations
  • What to do in the event of a fire
  • Equipment and good practise
  • Fire alarms.

Does your workforce need fire safety training?

Our fire safety online training courses are designed to help ensure your organisation complies with fire safety regulations.

We have a suite of Fire Safety Training courses designed to meet your organisation’s training needs.