If you think about it carefully in the combustion process, the question arises: why is the flame does not go out by itself? Because the combustion products are carbon dioxide and water vapor - a substance non-flammable, unable to support combustion. Therefore, the flame from the first moment of combustion must be surrounded with non-combustible substances, which prevent the inflow of air; without air combustion cannot continue, and the flame should go out.
Why is this not happening? Why the burning lasts continuously until there is a supply of combustible material? Just because gases expand on heating and, therefore, become easier. Only because of this, the heated combustion products do not remain in the place of his education, in close proximity to the flame, and immediately pushed up clean air. If the law of Archimedes did not apply to gases (or if there was no gravity), every flame, Pogorelsky little, extinguished itself.
Very easy to see how destructive effect on flame products of combustion. You often use it, without knowing it, to extinguish the fire in the lamp. How blow you a kerosene lamp? Blow into it from above, i.e, chase down the flame, non-flammable products of combustion; and it goes out, deprived of free access of air.