Optimum ventilation and airflow control in buildings?

Air quality, air flows in buildings, and ventilation are most important topics. Good air quality is however critically dependent also on other things than ventilation, e. g. source strengths, as is well known. The theme of our conference could also lead to the assumption that there is a simple connection between ventilation and air quality. As the public tend to see ventilation systems as responsible for bad air quality, it is important to state that there is no general criterion for good air quality possible to use in practice to control ventilation processes. Automatic ventilation control is still possible in specific cases only. The ventilation process depends on the total air exchange in the building, which is difficult to control. A related question is: what is acceptable as ventilation air? Is air leaking in through the outer wall acceptable? Is air supplied through the staircase acceptable? To answer such questions air quality criteria are needed too.