Question

when we exhale we release CO2.then how it helps in ignition of fire

Answer 1

The reason that blowing on a small flame (such as a candle or match) puts it out is that each instant of combustion depends on the heat generated by the previous instant to vaporize the fuel. Solid wood or paper and solid candlewax don’t react with oxygen; they must be heated up to and beyond the point where the are converted into gases in order to do so. By blowing, you carry the heat of the reaction away before it can be transferred to the new fuel, and so the reaction stops.

EDIT: After re-considering your question (“go up” is not normal English for what I think you are asking about), blowing to increase the intensity of a fire works by transporting more air to the fuel, so that oxygen consumed is replaced more quickly by fresh air. The exhaled breath does contain some oxygen, but you also entrain and move the surrounding air to carry it to the fuel.


Hope its help you.....!