Air circulation in housing

Air circulation in housing usually takes place through open doors, hallways or other gaps.
When replacing indoor doors, it is preferable to leave a small gap under them so that even in closed condition the air between rooms can be exchanged.
If doors are closed tightly, an overpressure condition may build in the room where air supply is provided, while the rooms with air exhaust channels will be in a low pressure condition.
It can be felt as a resistance in the process of opening or closing the door.