What fire extinguisher to use?

When choosing the right fire extinguisher, it is important to know that no single type of fire extinguisher can be used on all types of fires. Your fire risk assessment should identify which types of fires are most likely to occur in your building/premises, making this a good place to start.

This article will help you learn what different types of fire extinguishers are available, what different classes of fire you may come across and which extinguishers should be used to tackle them, if it is safe to do so.

The five types of fire extinguishers

The five different types of portable fire extinguishers are water, powder, foam, wet chemical and carbon dioxide (CO2). There are as many as 15 if you count the supplementary portable fire extinguishers. Anyone who may have to use a portable fire extinguisher should be trained by a professional to do so.

There is no single fire extinguisher which works on all classes of fire.

What are the different classes of fire?

There are six different classes (or types) of fire. There are:

• Class A – combustible materials caused by flammable solids such as wood, paper, and fabric
• Class B – flammable liquids such as petrol, turpentine or paint
• Class C - flammable gases: like hydrogen, butane or methane
• Class D fires - combustible metals, including chemicals such as magnesium, aluminium or potassium
• Electrical fires - electrical equipment: once the electrical item is removed, the fire changes class
• Class F fires - cooking oils and fats (typically a chip pan fire).

Which fire extinguisher can be used on each type of fire?

Advantages and disadvantages of the different types of portable fire extinguishers

Water (standard)

Advantages

• excellent penetration properties
• good absorbance of heat and quicker cooling effect
• long range jet, which prevents you from getting too close to the fire
• when heated, water turns into steam and evaporates
• does not create a mess or long term damage after the fire has been extinguished, and allows for a shorter business contingency plan.

Disadvantages

• limited to class A fires only
• water is an electrical conductor, making the extinguisher unsuitable if the class of fire has an electrical supply, or for use near live electrical equipment.

Water spray (water with additive)

Advantages:

• excellent suffocation properties
• quickly creates a cooling effect
• water, when heated, turns into steam and evaporates.

Disadvantages:

• limited to class A fires only
• leaves a small amount of residue after the fire has been extinguished
• water is an electrical conductor, making the extinguisher unsuitable if the class of fire has an electrical supply, or for use near live electrical equipment.

Watermist (de-ionised water)

Advantages:

• excellent suffocation properties
• quickly creates a cooling effect
• water, when heated, turns into steam and evaporates
• can be used on class A, B, C, F, and electrical fires at a 1m distance
• leaves almost no residue and damage.

Disadvantages:

• the fire extinguisher fire rating for class B, C, F and electrical fires is lower than other types of fire extinguisher aligned with this class of fires.

Dry powder extinguishers

BC powder

Advantages:

• can be used on
  • class A fires involving combustible solids like wood and paper
  • class B fires involving flammable liquids like petrol diesel, spirits and paints
  • class C fires involving flammable gases like methane and butane 
• forms a barrier which excludes oxygen and prevents reignition
• can be used in environments over a wide temperature range of -20°C to 60°c (EN models)
• twice as effective as foam on class A fires
• not as susceptible to frost as water based extinguishers.

Disadvantages:

• clean up can be costly and time consuming, as lots of residue is left after use
• visibility is reduced when discharged
• no or very limited cooling properties
• can cause corrosion on electrical equipment

High performance powder

Advantages:

• can be used on class D fires involving metals and flammable liquids like petrol diesel, spirits and paints
• forms a barrier which excludes oxygen and prevents reignition
• can be used in environments over a wide temperature range of -20°C to 60°c (EN models) 
• not as susceptible to frost as water based extinguishers.

Disadvantages:

• clean up can be costly and time consuming, as lots of residue is left after use
• visibility is reduced when discharged
• none or very limited cooling properties
• can cause corrosion on electrical equipment.

AFFF (foam)

Advantages:

• produces a foam that acts initially as a blanket, covering the surface area and smoothering the fire.
• improved cooling properties compared with other types of foam fire extinguisher (excluding water types).
• foam breaks down the liquid drains off and forms a film on the burning surface.
• foam helps to prevent re-ignition.
• AFFF can be used on class A and B fires.

Disadvantages:

• can’t be used on other types of fires.

Eco foam
Foam extinguishers work similarly to water extinguishers by having a cooling effect on the fuel. The foaming agent works by creating a barrier between the flame and the fuel.

Advantages:

• can be used on class A and B fires.
• suitable for use on electrical appliances, wood, paper and liquid fires.
• foam discharge is easier to clean up than powder.

Disadvantages:

• can be susceptible to frost.
• some residue is left after use.

Carbon dioxide (CO₂)

This type of extinguisher is most suitable for class B and electrical fires. They contain pure, compressed CO₂ (carbon dioxide) gas which is discharged through a horn as a strong jet of gas. These are often the most popular choice of fire extinguisher, and work by starving the fire of oxygen and therefore putting it out.

Advantages:

• smother fires more quickly in draught free conditions.
• carbon dioxide is a non-conductor, so can be used on live electrical equipment (so is often suitable for server rooms).
• leaves no residue and is not as damaging to electrical equipment as powder.
• suitable for class B fires – flammable liquids including petrol, diesel, spirits, and paint.

Disadvantages:

• should not be used in confined spaces as it is an asphyxiant gas.
• has limited cooling properties.
• offers no protection against reignition.
• a non insulated horn can cause frost burn if the user touches it when in use.
• other types of extinguishers will still be required for other types of fires.
• even indoors, as soon as the CO₂ dissipates any remaining embers can start reignition of the fire.

Wet chemical

Wet chemical fire extinguishers contain an odourless, clear fluid and are marked by a yellow label. They have their own classification called an F rating. These extinguishers are most suitable for use on deep fat fryers, and produce a light foam that rests on the hot surface and spreads itself over it until the entire surface is covered by foam, cutting off the oxygen supply.

Advantages:

• provides a fast reduction in the event of a class F fire.
• low chance of reignition.
• low pressure to reduce the chance of burning oil splashing and causing injury.
• clean up after use is quick and easy.

Disadvantages:

• the solution used in wet chemical extinguishers is alkaline, which means it can cause corrosion of some metals.
• the solution can cause irritation to the skin and eyes.
• not suitable for electrical fires.

Looking for fire extinguisher training? The FPA offer comprehensive fire warden training where you can gain hands on experience of using a fire extinguisher.

Please be aware that considerable efforts have been made to ensure the accuracy of the information contained within this article at the time of publication, however any legislative (or other) changes that come into effect after this may render the information out of date until it is reviewed and updated as part of the FPA’s content review cycle.