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CO2 Fire Extinguishers & How To Use Them 

From their colour and how to use them to what sizes they come in, here’s our complete beginner’s guide to CO2 fire extinguishers! 

CO2 fire extinguishers are unique in that from all the types of fire extinguishers, they are the only ones that can be used to extinguish electrical fires. This is because they use carbon dioxide which is a non-conductive gas and that makes them safe for use on electrical equipment and live cables.

Another advantage a carbon dioxide extinguisher has is that the gas, unlike water, powder or foam,  doesn’t leave a mess behind. It’s not just about the time saved in cleaning though. The main benefit is that it doesn’t affect the performance of the electrical equipment in the future. 

This is why CO2 fire extinguishers are often found in office buildings, server rooms, labs and mechanical rooms. You may also find a carbon dioxide extinguisher in a place where flammable liquids are stored because it can also be used on fires caused by flammable liquids.

How to recognise a CO2 fire extinguisher

The first thing to look out for is the fire extinguisher colour. A carbon dioxide extinguisher has a black label. If you happen to be in a fire emergency situation and you forget the colour codes in the commotion, read the label. It should clearly state “CO2” or “Carbon Dioxide” in large letters to make it as easy as possible to find out if you have the right extinguisher type. 

Another interesting thing that makes carbon dioxide fire extinguishers stand out from the rest is that they have no pressure gauge. Instead, they have a hard horn-shaped nozzle or a horn and hose (under 5kg). This is because the pressure in the canister is extremely high.  

Like all other fire extinguishers in the UK, CO2 extinguishers usually come in a red canister. However, you may also come across chrome CO2 fire extinguishers – those are made of steel or aluminium and are silver-coloured. The label will still be black and will still have all the necessary instructions printed out.  

How do CO2 fire extinguishers work?

Carbon dioxide is a type of gas but within the canister of a fire extinguisher, it is extremely pressurised (55 bar or 825psi), turning into a liquid. When you start using the extinguisher, the pressure drops and the liquid turns back into gas. Be careful though – the decrease in pressure is so quick that it can cause dry ice to come out of the nozzle. This makes it unsafe to use in tight, enclosed spaces. 

Fire extinguishers in general work by removing one of the three elements of the fire triangle. Carbon dioxide fire extinguishers displace oxygen, suffocating the fire. The gas is also cold, so it takes away some of the heat too. The reason why a CO2 fire extinguisher cannot be used on class A fires is because it may not be able to replace enough oxygen fast enough to stop the fire. There’s also a danger of reignition if the extinguisher is used on the wrong type of fire.  

How to use a CO2 fire extinguisher

First of all, you should only use a fire extinguisher if you have had the appropriate training. Also, you should never attempt to extinguish a fire if the fire is too big, spreading fast or out of control. Always make sure the fire alarm has already been raised and that you have a safe escape route before you attempt to use the extinguisher. 

With that out of the way, if you are in a situation where you need to tackle a small fire with a CO2 fire extinguisher, there are four steps to take:

  • Pull the safety pin
  • Aim at the base of the fire
  • Squeeze the lever
  • Sweep the extinguisher from side to side

One very important thing to remember about carbon dioxide fire extinguishers is that you should never hold the horn when discharging the extinguisher. The gas comes out at temperatures so low that it could freeze your skin and cause damage to your hand. Some models nowadays are equipped with frost-free horns, however, if you are not sure whether yours is one of them, err on the side of caution and keep your hands away from the horn. 

Another problem to consider is that CO2 fire extinguishers are NOT suitable for use in enclosed spaces. The carbon dioxide kills the oxygen in the fire but in a small area, it can also affect the quantity of breathable air in the room by reducing the oxygen levels, which can be life-threatening. 

One of the general rules of using a fire extinguisher is to never get too close to the fire. However, if you are too far, the extinguisher may not be effective. This is why if you are using a CO2 extinguisher, you should ideally stand between 3 and 8 feet (1 to 2.5m) away from the fire. 

Bear in mind that upon being discharged the carbon dioxide fire extinguisher will make a very loud discharge noise. This is normal, so don’t worry about it. 

Another thing that might surprise you is that the discharge time of a CO2 extinguisher is only 6 seconds. Because of that, you should not try to extinguish large fires with it. A fire localised to a single electrical equipment item is what these fire extinguishers are best suited for. 

CO2 fire extinguisher legal requirements

In a building where electrical equipment is used, you are required to have a CO2 fire extinguisher, minimum 2kg size. If you use equipment that is rated 415 volts, you need a 5kg CO2 extinguisher. 

Carbon dioxide extinguishers are usually paired up with a water or foam extinguisher which is suitable for extinguishing Class A fires. According to UK regulations, all extinguishers must be safely fitted to the wall or kept in a special cabinet. 

When a CO2 fire extinguisher is installed, it has to be commissioned by a specialist (competent person) before it’s used. As part of the commissioning process, a fire safety engineer will perform a series of checks to verify that your new extinguisher is fit for use and set up correctly. 

You are required to ensure that the extinguisher is properly maintained and serviced regularly, which usually means setting up an annual fire extinguisher service by a professional. 

Lastly, your CO2 fire extinguisher has to be replaced after 10 years even if they have never been used. If an extinguisher is discharged, it must be replaced immediately. 

CO2 fire extinguisher sizes 

CO2 fire extinguishers are commonly sold in the 2kg or 5kg varieties. Those are the ones found in commercial buildings that have electrical equipment. 

You could also buy bigger carbon monoxide extinguishers with the largest sizes going up to 50kg. Those are wheeled fire extinguishers due to their weight and are usually used in hospitals, airports, petrol stations, boats and other specific locations. 

Buy a CO2 Fire Extinguisher

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