Air movements in buildings

The indoor air quality depends on several different factors. One is the air flow or air movements within the building and through its external walls. These flows are governed by the type of leakage openings and the pressure differences across the walls and the air terminal devices. The pressure differences are caused by wind, thermal and fan forces. Mathematical models can be used to calculate the different air flow rates. A simple example is used to demonstrate magnitude and consequences of this air leakage for two different ventilation systems. Finally a recent survey of computer programs is reviewed. No program which calculates the air flows in detail was found to be available.