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19 Apr, 2023

Knowing your fire extinguishers is important when it comes to applying proper fire safety. Different types of fire extinguishers are suitable for extinguishing separate classes of fires. Identifying which one to use and have on your premises could be the difference between life and death.

There are five types of fire extinguishers: CO2 (Carbon dioxide), dry powder, foam, water and wet chemical. All these have specific functions which you can learn more about by visiting the MCFP Fire Extinguisher Guide.

In this blog post, we’ll be covering everything you need to know about CO2 fire extinguisher use.

What Are CO2 Fire Extinguishers Used For?

Carbon dioxide fire extinguishers are primarily used to extinguish electrical fires. Foam extinguishers have some effect on electrical fires, but nothing works as well for dousing fires on electrical equipment as carbon dioxide extinguishers.

Carbon dioxide forms a barrier between the source of electrical fires and the surrounding oxygen. This helps to suffocate the blaze and douse the fire.

CO2 fire extinguishers are also effective in extinguishing certain flammable liquid fires, known as Class B fires. There’s a fine line in this regard, though, and knowing your specifics about the different fire classes is essential. Why? Several types of flammable liquids don’t respond well to the addition of CO2 – a Class B fire from oil, for example, could get worse!

For electrical fires, though, there’s nothing better to use than CO2 fire extinguishers. Electrical fires generally start because of a type of electrical appliance overheating or breaking down. A short in some electrical wires, or a defective plug socket could also start an electrical blaze.

When you attempt to put out electrical fires or flammable liquid fires using a CO2 fire extinguisher, focus on the combustible electric equipment or burning liquid itself. CO2 fire extinguishers are not effective against fires in flammable solids.

If the fire has spread to a solid material like paper or wood, the fire risks have increased and you’ll need a Class A extinguisher to douse it.

It’s never advisable to use CO2 fire extinguishers, or any others, in confined spaces. The primary function of carbon dioxide extinguishers is to reduce the spread of oxygen to a fire. Within a confined space, low oxygen can be extremely hazardous. It could end up leading to asphyxiation.

CO2 fire extinguishers aren’t very useful outdoors. Weather elements like strong breezes or wind can disperse the CO2 before it finds its intended target.

CO2 fire extinguishers are usually found in two and five-kilogram containers. These should be positioned in locations where flammable liquid or live electrical equipment are common.

These areas include hospitals, schools, shops, offices, server rooms and data centres. Where flammable liquid is found, foam fire extinguishers will likely accompany CO2 fire extinguishers, in accordance with fire safety provisions.

How CO2 Fire Extinguishers Work

CO2 fire extinguishers hold liquid carbon dioxide in a highly pressurised environment. When the lever on a carbon dioxide fire extinguisher is used, the pressure inside the container is reduced. This results in the carbon dioxide inside converting to gas form. The resulting discharge is immensely cold due to the quick transformation of the fire extinguisher’s contents.

The resulting carbon dioxide gas emitted is virtually dry ice. It brings down the temperature of the fire’s flames by attacking the ‘heat’ corner of the combustion triangle. You should note that, although the cooling effect of a CO2 fire extinguisher is effective, water and foam extinguishers actually cool flames more.

As carbon dioxide has a greater mass than oxygen, the rapid rate at which it leaves the fire extinguisher container displaces any oxygen feeding the flames of electrical fires or burning liquid. The CO2 forms a barrier between the fire and the surrounding air, cutting off the ‘oxygen’ corner of the combustion triangle to douse the flames.

Advantages of CO2 Fire Extinguishers

  • Best for electrical fires: CO2 doesn’t conduct electricity. For this reason, CO2 fire extinguishers are more effective for extinguishing electrical fires in live electrical equipment than any other type of fire extinguisher.
  • Cause no damage: CO2 is a non-corrosive gas. As such, there is no solid material included making it a pure extinguishing agent. CO2 fire extinguishers leave no residue behind on surfaces after use.
  • Long-lasting and reliable: CO2 extinguishers last longer than any other extinguishers. An extended service is only required after 10 years.
  • Can be used on some Class B fires: CO2 fire extinguishers are also good at dousing Class B fires involving certain types of flammable liquids.

Disadvantages of CO2 Fire Extinguishers

  • More dangerous to use: Users can experience freeze burn if touching CO2 fire extinguishers on the pipe leading to the horn during use.
  • Can’t be used in small spaces: CO2 fire extinguishers emit CO2 which replaces oxygen in the air. As such, their use in confined spaces could lead to asphyxiation.
  • Don’t work on all types of fires: Carbon dioxide fire extinguishers are of no use in extinguishing fires in flammable solids.
  • Not effective outdoors: CO2 fire extinguishers are limited outdoors, as the CO2 gas can be dispersed by wind.
  • Worse for the environment: CO2 fire extinguishers are less friendly to the environment than other types of fire extinguishers.
  • Risk of reignition: After CO2 dissipates, any remaining hot embers could reignite a fire.

Maintenance and Inspection

You have to service your CO2 extinguishers once every 12 months. This is the same fire safety stipulation as for the vast majority of other extinguisher types. Unlike most others, though, you can save costs as you needn’t refill them every five years. A CO2 fire extinguisher only requires refilling once a decade.

Upon servicing, a CO2 extinguisher is weighed to establish whether it is still full. A CO2 fire extinguisher doesn’t have a pressure gauge. For this reason, the service technician must use finely-calibrated scales when weighing.

After 10 years, carbon dioxide extinguishers require compulsory refurbishment, which includes replacing the safety pin. As such, it is often easier and more cost-effective to simply replace a CO2 fire extinguisher instead.

Regulations and Standards

According to UK government fire regulations and standards, any commercial building that holds live electrical equipment must have at least a two-kilogram CO2 fire extinguisher on the premises. If there is heavier-rated equipment of an electrical nature on site (415 volts +) the CO2 extinguisher needs to be at least five kilograms.


CO2 fire extinguishers are not difficult to operate but still need to be used carefully. Without the correct level of care, you could do yourself serious injury. The safest way to use a CO2 extinguisher is to note the following instructions:

Firstly, remove the safety pin to break the anti-tamper seal and make the extinguisher ready for use. Avoid the extinguisher horn, and the pipe leading to it, when holding. These parts get extremely cold when releasing the CO2, and touching them could result in cold burns. Of course, if your extinguisher has a frost-free horn, you don’t have to worry.

From a reasonable distance away (one metre is safe), pull the lever and use the CO2 spray to put out the fire. The type of fire you’re extinguishing defines the position you should aim the extinguisher towards.

For electrical fires, aim the spray onto the fire directly. If you’re dousing a fire caused by flammable liquids, start by spraying at the fire’s base and raise the nozzle slowly higher into the flames.


You must ensure that your CO2 extinguishers are stored in temperatures between -30 degrees and 60 degrees centigrade. The extinguishers should also be stored out of the sun, so make use of covers or blinds if need be. Alternatively, keep your extinguishers away from entrances or windows that let in the sunlight.


As part of the UK Regulatory Reform (Fire Safety) Order 2005, businesses need to provide reasonable training in fire safety to workplace staff. It’s also necessary to appoint fire marshals and wardens.

Fire safety training is crucial for making sure your staff is safe from fires, and it’s the law. Contravention could result in fines or worse. At MCFP, offer a Fire Awareness Training Course to improve in your workplace.


At MCFP, we have the knowledge and experience to assist you with your fire protection needs and questions. Contact us for your fire risk assessment and workforce’s mandatory fire training.