CO2 Fire Extinguishers

So which fires are they suitable for?

CO2 extinguishers use only carbon dioxide gas which is compressed to a pressure of 55 bars. It is also a clean extinguishant leaving no mess or residue. This fire safety equipment puts out class B fires which are most fires in flammable liquids such as petrol, tars, oils, solvents, and alcohol. Class B fires also include flammable gases such as propane which you find in a lot of camping inventories. CO2 extinguishers are also recommended for use with electrical equipment. They are not suitable for class F fires however, such as those that occur with cooking oil and grease. The pressure of the extinguisher is so great that it would like spread a chip pan fire into surrounding areas.

CO2 fire extinguisher use and guidance

There is a lot of pressure in the extinguisher and so if it gets hot that pressure will grow past the breaking point. There is a safety valve in place so that should over pressurisation occur, the gas is allowed to escape without breaking the extinguisher’s exterior. The problem with this is it leaves the amount of CO2 in the tank greatly diminished, not what you want in the middle of a fire. So what should you do? Just be mindful not to keep it near radiators or where it could come into contact with direct sunlight and you will be fine. Try to place them near where there is the greatest risk of fire or failing that, near the fire exits. A CO2 extinguisher should never be used without the horn having been fitted prior. The amount of pressure in the tank is more than what is optimal and the horn is responsible for reducing this pressure. Without it, the extinguisher would discharge far too quickly and likely injure the user with the sharp recoil. Be sure to ask your supplier for an extinguisher with a frost-free horn. You will want this because CO2 gets cold, very cold, so cold that with extended use you can get frost damage to your skin. Frost-free horns are designed to hold up against the freezing gas and can be held without transferring the cold to the user. It is still recommended not to hold the horn however. Rest assured, all our CO2 extinguishers come with frost-free horns.


  • Do check the extinguisher is fully charged and the safety bin is unbent
  • Do stay a safe distance from the fire and remove the pin
  • Do aim the horn at the base of the fire
  • Do switch off the power to any electrical equipment first
  • Do squeeze the lever, slowly at first, and move closer to the fire as it gets smaller
  • Do make sure the fire is truly extinguished (they can reignite when you’ve used a CO2 extinguisher)


  • Don’t use it in a small confined space. The CO2 released into the air could cause you to asphyxiate as it replaces the oxygen.
  • Don’t use with Class F fires
  • Don’t hold the extinguisher by the horn

From liquids to electronics

CO2 extinguishers were originally created to deal with liquid fires like what you would expect to encounter at a petrol station or on an oil barrel. CO2 was chosen as an extinguishant because the inert CO2 gas starves the fire of oxygen and therefore puts out the fire. Fast forward to today and these extinguishers are more often used for electrical fires since the CO2 does not leave any residue, evaporates quickly and so does not damage the computers any more than the fire has already done. You may think saving a computer on fire is a lost cause but when extinguished with CO2 data can often be backed up from the hard drives and the components salvaged. They are also good at preventing a fire from occurring because much of the surrounding oxygen will have been replaced with CO2 and the temperature will have dropped.  

Fire! Where is the CO2!?

You can recognise a CO2 fire extinguisher by the black label with the words CO2 or ‘Carbon Dioxide’.  There is no pressure gauge at the top and no hose. If it is manufactured to BS EN 3, as all of our extinguishers are, then they should have a red body and a black band. If you have a CO2 extinguisher with an entirely black exterior then you need to dispose of these as they no longer comply with British Standards.

Is a CO2 fire extinguisher right for our business/premises?

These extinguishers should be on all premises with an electrical fire risk. Typically they will be placed in premises such as:

  • Schools
  • Hospitals
  • Shops
  • Offices
  • Server rooms
  • Construction sites
  • Restaurants and kitchens
  • Vehicles