The ventilation standard was investigated in a large number of school buildings located in Gothenburg, Sweden as part of a current large-scale renovation programme. This article reports on experiences from the reconstruction work involved. Results from air quality measurements comprising TVOC (total volatile organic compounds) and CO2 measurements are presented. The results show that the indoor air quality is considerably influenced by outdoor contamination sources and that cleaning products and floor polish can, temporarily, add to the pollution content in classrooms.