Poor indoor air quality is a large problem in Swedish schools, since the health of occupants may be affected. The building itself is often in focus and other building-related problems may be neglected. The hypothesis of this study is that factors other than the building itself have decisive influence on indoor environment. An assessment of these nonspecific building-related reasons for bad indoor environment has been made in the present work using surveys combined with particle measurements and comfort measurements (air humidity and air temperature). People are experiencing poor indoor air quality, the air is too dry and the temperature is uneven and uncomfortable indoors in the winter. It is important to highlight the problem of indoor environments with high particulate emissions especially in the range from 5.0 microns and larger since they are conveyers of allergens and bacteria, combined with dry air. An interesting observation regarding the ventilation system is that mechanical systems are tending to generate drier indoor air than the natural ventilation system. Results show that it is possible to decrease emissions through eliminating activity-related sources of airborne contaminants and better the comfort indoors with relatively simple measures.