Types of Fire Extinguishers and Their Uses
In this blog post, we’ll look at the different types of fire extinguishers and their uses.
So, you can understand which types of extinguisher you need in your workplace.
And, importantly, know the correct extinguisher to use in the event of a fire!
In addition, you can find guidance on the different classifications of fires, when to tackle a fire and where to position your extinguishers.
We’ll kick off by discussing the classification of fires.
Classes of Fire
In the UK, fires are categorised depending on the source of fuel.
Below are the different classifications:
Class A – Solid combustible materials e.g. wood, paper, textiles, rubbish, etc
Class B – Flammable Liquids e.g petrol, diesel, oil
Class C – Flammable Gases e.g. natural gas, propane
Class D – Combustible metals e.g. Lithium, Sodium, Magnesium
Class F – Cooking Oils/Fats e.g oil in deep fat fryers
Electrical Fires (Class E) – Electrical fires e.g. short-circuiting equipment, overloaded cables
Class E doesn’t technically exist because electricity is a source of ignition rather than a fuel. However, electrical fires can electrocute those using an incorrect extinguisher. Therefore, these types of fire require special attention.
Note: Once you turn off the electricity supply, you can categorise the fire into one of the appropriate of the classes above depending on source of fuel.
Now, we understand the different classifications, we will look at which extinguishers we can use on each.
Methods of Extinguishing Fires
When extinguishing a fire your main aim is to remove one of the three elements of the fire triangle.
Oxygen, Heat or Fuel.
Fire extinguishers work in different ways to achieve this goal as you’ll see below.
Some cool the fire by removing the heat. Others smother the fire by removing oxygen. And, the rest starve the fire by creating a barrier between fuel and flames
So, let’s look at the different types of extinguisher and their uses.
Types of Fire Extinguisher
Water Fire Extinguishers
We’ll start by looking at water extinguishers.
Of which, three important variants exist:
Standard Water Extinguisher
Used on: Class A fires
Don’t use on: Electrical fires (Class E – can lead to electrocution). Class B and C (spray can spread flames). Class D and F.
How it works: The water spray lowers the temperature of the burning material so the fire can no longer burn.
Method of Extinguishing Fire: Cooling
How to Identify: ‘Water’ written in white on a red background. See above picture.
Pros: Rapid extinguishing; no environmental impacts.
Cons: They only extinguish Class A fires
Water Spray Extinguisher
Used on: Class A fires
Don’t use on: Electrical fires (Class E – can lead to electrocution). Class B and C (spray can spread flames). Class D and F.
How it works: These extinguishers have a specific nozzle that works at high pressure. The resulting spray has a higher surface area than ordinary water extinguishers which increases the cooling rate and therefore the rate of extinguishing the fire.
Method of Extinguishing Fire: Cooling
How to Identify: ‘Aqua Spray’ written in white on a red background. See above picture.
Pros: More effective than a standard water extinguisher; no environmental impacts.
Cons: Again, they only extinguish Class A fires.
Water Mist Extinguisher
Used on: Class A, B, C, F and Class E (up to 1000V if dielectric tested to 35kV)
Don’t use on: Class D fires.
How it works: Deionised water passes through a supersonic nozzle which turns water into microscopic droplets. When in use, the fine mist suffocates and cools the fire.
Method of Extinguishing Fire: Cooling & Smothering
How to Identify: ‘Water Mist’ written in red on a white background. See above picture.
Pros: Covers a wide range of fire classes; no environmental impacts; Uses no chemicals so suitable for kitchens and food production facilities.
Powder Fire Extinguishers
Currently, two types of powder extinguishers are available…
Dry Powder Extinguisher
Used on: Class A, B, C fires. Class E fires (although, susceptible to reignition)
Don’t use on: Class D and F fires
How it works: The powder forms a barrier between fuel source and flames starving the fire.
Method of Extinguishing Fire: Starving the fire.
How to Identify: ‘Powder’ written in white on a blue background. See above picture.
Pros: They work on 3 most common classes of fire
Cons: Reignition can occur because the powder doesn’t absorb the heat; Dangers associated with inhalation (not recommended inside buildings or small spaces); messy after discharge.
L2 and M28 Dry Powder Fire Extinguishers
Used on: Class D fires. M28 – Sodium, Magnesium, Aluminium, etc excluding Lithium. L2 – Sodium, Magnesium, Aluminium, etc including Lithium.
Don’t use on: Class A, B, C, E, F
How it works: A specially designed hose sprays the powder over the combustible metal. This creates a shield which prevents the metal from encountering the cause of combustion i.e. water/oxygen.
Method of Extinguishing Fire: Interfering with Chemical Reaction.
How to Identify: ‘Powder’ written in white on a blue background. Distinctive hose. See above picture.
Foam Fire Extinguishers
Used on: Class A and B fires. Class E fires (up to 1000V if dielectric tested to 35 kV).
Don’t use on: Class C, D, F
How it works: Foam forms a barrier on the surface of the flammable liquid which prevents flammable vapours combusting. Similarly, with solid materials, the foam forms a barrier between the combustible material and the flames.
Method of Extinguishing Fire: Smothering and Starving.
How to Identify: ‘Foam’ written in red on a cream background. See above picture.
Pros: More versatile than water; more effective than water on Class A fires
Cons: Leaves a messy residue
CO2 Fire Extinguishers
Used on: Class B and E fires
Don’t use on: Class A, B, D, F
How it works: Carbon dioxide replaces oxygen thereby smothering the fire.
Method of Extinguishing Fire: Smothering
How to Identify: ‘Carbon Dioxide’ written in white on a black background. See above picture.
Pros: No messy residue
Cons: Can suffocate users in confined spaces; Carbon dioxide dissipates quickly leading to reignition in some cases.
Wet Chemical Fire Extinguishers
Used on: Class F fires
Don’t use on: Class A, B, C, D or E fires
How it works: A fine mist helps cool the flames whilst chemicals react with the cooking fat/oil to produce a substance that creates a barrier between the flames and the oil (fuel source).
Method of Extinguishing Fire: Smothering
How to Identify: ‘Wet Chemical’ written in red on a yellow background. See above picture.
Fire Blankets
Used on: Small oil pan fires and people who have caught fire
Don’t use on: Class A, B, C, D, E and large Class F fires
How it works: Fire blankets smother fires by restricting their oxygen supply.
Method of Extinguishing Fires: Smothering
How to Identify: Red case with ‘Fire Blanket’ written in white.
We’ll finish our discussion about fire extinguishers with some general advice…
General Advice about Fire Extinguishers
When to Fight a Fire
There are certain times when fighting a workplace fire is sensible and others when it’s not.
You should only attempt to fight a fire when:
- The fire alarm has been raised
- Emergency services have been notified
- Fire is contained and isn’t spreading
- A clear escape route is available
- You have the correct fire extinguishers
In contrast, you shouldn’t attempt to fight a fire if:
- A fire is larger than a bin (General Rule)
- You need more than 1 extinguisher
- The room is filled with smoke
- There is no clear escape route
- The fire involves gas cylinders or chemicals
- The correct extinguisher is not available
Locations of Fire Extinguishers
You’ll need to place your extinguishers in the right places so that you can use them effectively should a fire occur.
Below are some general guidelines to follow.
You should fix fire extinguishers to the wall or on a stand in their designated areas (which should be clearly visible). This is to avoid people moving them from the areas you need them most.
In addition, your extinguishers should be kept at a suitable distance from risk areas and along escape routes.
General guidance suggests placing extinguishers at the following distances from:
- Class A Risks –> 30 metres
- Class B Risks –> 10 metres
- Class C Risks –> 30 metres
- Class D Risks –> Case by Case
- Class F Risks –> 10 metres
Adjust these down if you’ll need to get through doorways to the hazard as this will add crucial seconds.
Furthermore, each extinguisher should have a corresponding sign above it which details its contents and the classes of fires it extinguishes.
Replacing Fire Extinguishers
Extinguishers don’t last forever.
They each have a shelf life and need servicing annually by a competent person e.g. a fire extinguisher engineer.
And, if they are found to be damaged, discharged or cannot be used safely, they’ll need replacing.
Alongside an annual service, your responsible person should inspect your extinguisher(s) weekly or monthly to ensure they are in good working condition.
Then, after 5 years (10 years for CO2 extinguishers) your extinguishers need replacing regardless of condition.
Fire Ratings
Every extinguisher has a fire rating.
This rating contains a number and letter i.e. 13A.
The letter gives the fire classification (so here a Class A fire).
And the number notifies you about the size of fire it can extinguish (the larger the number the bigger the fire).
A fire extinguisher can have several ratings depending on which fire classes it can extinguish.
For example, a foam extinguisher will have 2 ratings; one for Class A fires and another for Class B fires.
Conclusion
After reading this post, you should have a better idea of which extinguisher (s) you need in your workplace.
And, you know which extinguisher to grab in the event of a fire.
Both of which help keep your workplace that little bit safer.
Did you learn something you didn’t know after reading this post?
If so, what was it? Let us know in the comments!
