Adequate ventilation with the "right amount of air, to the right place and at the right time" are important factors for achieving a good indoor climate. Thus it is of prime importance that the ventilation system is working properly. Using traditional methods, it is a very time consuming, and some times even impossible, task to balance ventilation systems to achieve correct air distribution. In most countries the growing concern about Indoor Air Quality has resulted in Building Codes demanding increased ventilation rates.

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.