Circulation of fresh air, fundamental to a healthy indoor garden, an exhaust fan creates ventilation.
Merriam-Webster Online Dictionary
ventilation (noun)1.
the act or process of - ventilating
2.
a) circulation of air - a room with good ventilation
b) the circulation and exchange of gases in the lungs or gills that is basic to respiration
3.
a system or means of providing fresh air
Airflow, Circulation, Aeration, Venting, Air Exchange