People spend most of their time during the day in closed areas where they should feel themselves fresh and healthy to work, to rest, to think, to decide and to get in action.

The indoor environment should not interfere with the comfort of the household, eg. with high noise levels, overheated rooms or poor lighting conditions,

As shopping malls are densely occupied spaces with a metabolic production of CO2 by the occupants, the CO2-concentration is directly dependent on the ventilation rate.