Ventilation is the mechanical system in a building that brings in "fresh" outdoor air and removes the "contaminated" indoor air. In a workplace, ventilation is used to control exposure to airborne contaminants.
Proper ventilation keeps the air fresh and healthy indoors. Like the lungs, homes need to be able to breathe to make sure that fresh air comes in and dirty air goes out. Air indoors can build up high levels of moisture, odors, gases, dust, and other air pollutant
Ventilation is especially required for commercial and industrial spaces to control indoor air quality by diluting and displacing indoor pollutants. Ventilation can also be used to control temperature, humidity and air motion.