This study is a part of a broader research programme established by CISBO ( Centre for Indoor air and Health in Dwellings). The purpose of the centre is to increase the general knowledge and to provide information on indoor air quality and related Health effects. The study may contribute with basic information on underlying pathophysiological mechanisms involved in human responses to these pollutants and in their interactive effects. The study includes as methods and techniques to detect minor changes in biomarkers suggesting early effect of exposure. These analyses will give information at a high sensitive level about the exposure effects on biomarkers for an array of symptoms and reactions.