Carbon dioxide is heavier than oxygen gas. It therefore displaces the oxygen gas around a flame. Without oxygen, the combustion reaction will stop and the flame will be put out.
Further Explanation:
In order for a combustion reaction to happen, three components must be present: fuel, oxygen, and heat to cause ignition. When one of these three is removed, the combustion reaction will stop.
CO2 fire extinguishers use the difference in mass of the CO2 and oxygen molecules to stop the fire. Since CO2 is heavier, it will displace any oxygen molecules that are around the flame. When this happens, the supply of the oxygen will be limited or cut-off and the fire will eventually be put out because of the lack of oxygen. This ability to displace oxygen is also what makes using CO2 as fire extinguisher quite dangerous for the user since it pushes away the oxygen that is needed for respiration.
Other ways to put out fire include spraying liquids that absorb the heat to avoid spreading the fire further or spraying substances that coat the fuel (flammable materials) to avoid contact with oxygen gas which can lead to further combustion.
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Keywords: carbon dioxide, fire, combustion
