Fire also sucks in air it doesn’t need at all. This mainly happens with an open fire, such as a fireplace. The excessive amount of air that disappears through the chimney is ballast air and it mainly cools. “Burned from the front, frozen at the back,” people said in the Middle Ages when standing in front of the fireplace. Frozen from the back by the flowing ballast air which can be 1000 m3 per hour with a fireplace.
A fire that does not use as much air burns in a stove. Because a stove is closed and the air supply can be dosed, only 10 m3 of fresh air is needed to burn 1 kg of wood. Usually, that amount of air is there where the stove is. At least it should be, because we, the stokers, also need fresh air. Even more than the stove.
An adult stoker needs about 30 m3 of fresh air per hour. This is due to the CO2 we breathe out that must be diluted. You could say, if the stoker can breathe, the stove can too. But with almost 1000 m3 per hour, the fireplace is not necessarily.
The air consumption of a fireplace is so great that a separate supply is necessary. Unless your house has not been renovated since the Middle Ages. A separate supply is not necessary for a stove, but in some cases the house is so isolated that a little extra air is sensible. Most stoves are specially prepared for their own fresh air supply. Via a hose, directly from the outside.
So that the fire stays on.