The measurements of formaldehyde concentrations and the investigations on the mode of living in student dormitories were carried out with the purpose of understanding the relationship between the living style and the actual indoor air pollution by chemical substances. As for the formaldehyde concentrations, the detector tube and the DNPH-passive method were used. The formaldehyde concentrations tended to decrease as years passed. However, four to five years after construction; the concentrations sometimes exceeded the guidelines (0.08 ppm). Specifically the concentrations tended to become high under high temperatures in summer when air-conditioners were in use. However, it was possible to reduce them by keeping the windows open or turning on ventilation fans. Therefore, along with the adequate choice of building materials and their quantity, due consideration for ventilation by residents is deemed effective and preventive against high exposure to chemical substances.