Natural ventilation is the exchange of air without the use of powered devices. It is of a gravitational nature, i.e. it is caused by the difference in temperature and air pressure inside and outside the room.
A variation of natural ventilation is infiltration, airing and aeration.
Infiltration is an example of unorganized ventilation. It then occurs, when outside air flows in through the open door, gaps and other leaks.
Airing takes place then, when we use the difference in air pressure to replace it by periodically opening doors and windows.
Aeration we call the continuous exchange of air through the openings connecting the rooms with the surroundings, using temperature and pressure difference. It is organized natural ventilation and may be combined with mechanical ventilation. The most common inlet openings are wall exhaust ventilation ducts. The intensity of air exchange is increased thanks to the use of vents on the roof, which increase the air draft in the ventilation ducts.