The quality of indoor air, which has considerable influence on human's well-being and health is diminished by pollution with up to sixty volatile organic compounds (VOC). The determination of the pollutants is feasible using active and passive sample collection combined with gas chromatography - mass spectroscopy. One innovative goal of the proposed project is the development of a practicable calibration system allowing precise VOC quantification. This includes acquisition of intimate knowledge of identifying the various compounds. Another aim refers to the comparison of active and passive sampling methods in different fields of application. In this context sample preperation using thermal desorption or solvent extraction has to be valued. Furthermore sampling and determination of reactive substances i.e. alcohols and esters has to be improved. Reliable and reproduceable quantitative determination of VOC is desirable in order to establish equal legalized maximum concentration levels of indoor air pollutants in the whole Community.