Since the cost of energy is increasing sharply a trend to conserve energy in the indoor environment and in addition to improvements in thermal insulation, two possible solutions are adopted. The first one is to provide reduced air gaps and opening for newly constructed buildings to minimise the infiltration of outdoor air. The second one is to reduce the ventilation rate or the fresh air supplied in air conditioned buildings. These two solutions are the reason for some serious problems of indoor air quality.
In order to save energy, i.e. ventilation heat losses, the fresh air change rate should be adapted to the prevailing need. Even though it is a fact that reducing the fresh air change rate will result in a ventilation heat gain, the fresh air flow rate should not be kept too low, so that pollutants, humidity and body odour can accumulate. The results of measurements in a climatic chamber and in a lecture theatre show a significant relationship between the concentration of carbon dioxide and body odour of the indoor air under nonsmoking conditions.