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Keep Your Air Pressure Positive
March 18, 2011 - Contact FacilitiesNet Editorial Staff »
Operate your building at a slightly positive pressure with respect to the outdoors.
The amount of outside air supplied to a building should slightly exceed the amount of air that is exhausted. The imbalance between the supply and exhaust air creates a positive pressure inside the building relative to the pressure outside. This positive pressure forces air out of the building through open doors and cracks around window and door seals.
The airflow being forced out of the building prevents the infiltration of unconditioned and unfiltered outdoor air as well as the infiltration of ground level pollutants, such as car exhaust, pesticide/herbicide odors, pollen, etc.
The difference between the amount of outdoor air supplied to the building and the amount of air exhausted should be only large enough to maintain the positive pressure inside the building relative to the outdoors. A substantial pressure differential could result in the excessive loss of conditioned air, leading to increased energy costs. At an extreme, it could even damage systems like the roof, so proceed with caution and a light hand.