While CO2 fire extinguishers were originally developed to fight fires involving burning liquids (Class B) such as petrol, they increasingly get used on electrical equipment such as electrical cabinets and computers, as the CO2 gas does not leave any residue and causes no damage to electrical installations. The gas coming from the CO2 fire extinguisher is, however, very cold and sensitive electronic boards might get affected. The traditional use of CO2 fire extinguishers, fighting burning liquids, is increasingly tackled with AFFF foam fire extinguishers, as the foam carpet on top of the liquid cools the liquid down and stays in place stopping the supply of oxygen after the fire is extinguished, preventing re-ignition. On the other side, the CO2 from a CO2 extinguisher would eventually disperse and there could be the risk of re-ignition if the fluid is still hot.
CO2 fire extinguishers contain CO2 gas under very high pressure of over 50 bar. The gas, as it is accelerated and expanded through the extinguisher horn or nozzle, gets very cold and care must be taken when holding the horn or pipe leading to the extinguisher horn to avoid freeze burns on your hands. You should preferably purchase CO2 extinguishers with frost-free or double lined horns.
If the installation location of the CO2 extinguisher is near a radiator or in direct sunlight the pressure in the cylinder increases rapidly. To prevent the bursting of the extinguisher body the extinguisher head has a safety valve built in. This is usually covered by a plastic cap. When this safety valve opens up to release pressure, the little cap is blown off and the CO2 gas is released until the pressure has been reduced.
And of course, make sure you do not install CO2 fire extinguishers near radiators or in direct sunlight.
As CO2 fire extinguishers do not have display pressure gauges, it is not possible to see how much CO2 is left in the extinguisher. During the yearly extinguisher service the engineer will therefore weigh the extinguisher and compare the result with the weight from the last inspection which has been recorded on the service label on the back of the extinguisher. Very fine weighing scales must be used, as small deviations of weight have a strong bearing on the filling status of the extinguisher.
CO2 extinguishers do not need refilling after five years, as most other extinguisher types do. The Co2 extinguisher only needs refilling or replacement after ten years