Of all the different types of fire extinguisher available when and where to use a Carbon Dioxide fire extinguisher is the least well understood. A CO2 fire extinguisher discharges gas under pressure replacing the air and more specifically the oxygen in the air with inert Carbon Dioxide gas which does not support combustion. Oxygen is essential for combustion so excluding it smothers the fire. Theoretically applying CO2 will extinguish any type of fire but in practice this is not always the case.
What is a CO2 Fire Extinguisher?
A CO2 extinguisher contains liquid Carbon Dioxide which converts to a gas when discharged into the air. This conversion from liquid to gas requires heat which it draws from the surrounding air such that the gas discharged is extremely cold hence the special insulated discharge nozzle to prevent “cold burns”. Do not be misled into thinking this cold discharge which is confined to the immediate point of discharge will cool the fire. As the gas continues to expand it heats up quickly so in general CO2 fire extinguishers are not recommended as a first line of defence for controlling Class A fires involving combustible solids. They will smother the fire, particularly if discharged in a relatively confined space but without a cooling element the solids may continue to smoulder and reignite.
When should you use a CO2 Fire Extinguisher?
Where Carbon Dioxide extinguishers are very effective is in controlling fires involving flammable liquids since it is the vapour that is burning and this is quickly smothered by the replacement of oxygen with CO2. Provided the initial source of heat causing the fire has been removed reignition is unlikely.
In today’s technological age offices, homes, retail premises, in fact virtually all business premises are full of high tech equipment containing delicate circuitry and expensive sophisticated electronics. As CO2 is inert, electrically non-conductive and dissipates quickly into the atmosphere without leaving any harmful or corrosive residue a 2kg CO2 fire extinguisher is the must have in most organisations for suppressing fires in electrical and electronic equipment.
On a precautionary note remember that CO2 can cause asphyxiation if inhaled and be sure to kill the power supply if possible before tackling an electrical fire.