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Residential indoor air quality, historically, has not been a major concern because the envelope and window leakage provided inhabitants with sufficient outdoor air. Older residential buildings are sufficiently leaky such that infiltration alone can meet the minimum outdoor air requirements for residential ventilation. In an increased environmentally conscious society, many individuals have become more aware of their resource consumption, and are implementing enclosure draftstopping, attic insulation, and window replacement.
Mechanical ventilation systems have evolved from passive gravity vents (circa 1900) by adding modifications to improve comfort, occupant health, and energy efficiency. Early on, the maintenance of the system basically related to making sure the furnace was on and the windows would open. If you were lucky the school might have draft deflectors on the windows so the wind would not blow directly on your head.