The infiltration ratios of pollutants from concealed spaces to indoor spaces were measured using a tracer gas method in a structure model and detached houses. The results are the followings:
1. The infiltration ratios from beam spaces were very high and those from crawl spaces and truss spaces were not low.
2. The infiltration ratios became higher when indoor spaces were decompressed by exhaust ventilation systems.
3. It is necessary to prevent the infiltration of pollutants from concealed spaces to indoor spaces and to keep air quality of concealed spaces.
