Sources of pollutants in indoor air.

In order to ensure an impeccable indoor air quality, it is important to do so, whenever possible, by means of source-control. In particular, this general principle should be applied with regard to contamination originating from building materials and furnishings. For such materials, quality requirements should be established to keep the concentration of emitted pollutants below admissible limits. In the case of building materials, a general declaration of all constituents should be mandatory and carcinogenic compounds like asbestos and benzene should be prohibited for use in indoor environments. If the emission of a specific pollutant cannot be avoided, its concentration in indoor air can be kept below the tolerated limit by increasing the ventilation. Increased concentrations of nitrogen dioxide due to the use of combustion appliances in kitchens and bathrooms can be avoided by exhausts. In geographical areas with high radon emission, however, corrective measures have to be evaluated individually. To eliminate the contaminants originating from human activities (e.g., carbon dioxide, body odours), adequate ventilation is required and depends on the occupancy and the use of the room; to maintain an acceptable air quality, the carbon dioxide concentration should not exceed 0.1-0.15%. Increased ventilation also reduces acute irritations if smoking is allowed. Here, the required air supply is dependent on the degree of annoyance which is considered to be acceptable to the user of the room. Acceptable indoor air quality can largely be maintained today because of the extensive knowledge and experience now accumulated in this field. However, the complex relationships between air quality and human health require further study. More research in the field of building materials is particularly desirable.