Hotels can be subdivided into different categories – hotels for business people, leisure travellers, motels, budget hotels, luxury hotels, convention hotels and conference centres etc. However, they all have one point in common: they rent rooms and try to provide guest comfort. Every hotelier knows that if a room is not sold, there is no possibility of making up the loss the next day: the life expectancy of the hotel product is very limited. Viewed from the outside, there is a tendency to adopt global technical solutions for providing occupant comfort including thermal (wellbeing), olfactory (air quality) comfort, with the result that technical systems in hotels may be designed, installed and operated in a similar manner to banks, shopping malls or large office buildings.