Abstract
In order to make clear the relationship between the chemical substances concentration and symptom of sick house syndrome, an investigation of 30 sick houses in Japan has been done for 8 years. Chemical substance concentrations show a decrease as the building age increases. However, there are some houses where concentrations increase due to low air change rate, use of moth crystals for clothes and new furniture. Because there was the case where the improvement of indoor air quality has relieved occupant's symptoms, it must be important to take measures such as ventilation frequently, non use of chemical products or use of low chemical products in the long term to treat “SHS”.