A few studies have provided information on longitudinal trends in VOC concentrations and emissions in new houses (Lindstrom et al., 1995, Hodgson et al., 2002). In four manufactured houses, the area specific emission rates of formaldehyde and hexanal were generally similar at the beginning and end of the study period demonstrating that the sources of these compounds were not depleted rapidly (Hodgson et al., 2000). In existing, occupied residential units, seasonal trends in VOC concentrations have been observed in a cross-sectional study in three German cities and in a longitudinal study of ten apartments (Schlink et al.,.
