ABSTRACT
Objective To explore the source and control of radon in high radon houses in geothermal fields; Methods Radon concentration in indoor and soil was measured by ATD detector in winter and summer; radionuclides in building materials were measured by gamma-ray spectrometry; radionuclides dose rates of building materials were measured by 6150 A D/ 6H X-γ ray detector; and radon reduction technology was applied to one of the houses;Results The average radon concentrations in 32 rooms were （106.4 ± 63.7） Bq/m3 (summer) and （421.3 ± 138.2） Bq/m3 (winter), and the concentrations in 12.5% (summer) and 96.9% (winter) of the rooms exceed 150 Bq/m3. The average radon concentration in soil around buildings was 12890 Bq/m3 (n = 24), which is 1.7 times of the typical soil radon concentration in Beijing (7600 Bq/m3). After soil decompression, the radon concentration in the house could be reduced to less than 100 Bq/m3. The radon reduction rates of active decompression and passive decompression were 94.6% and 71.4%, respectively. Conclusion The effect of soil decompression on reducing radon concentration in the bottom rooms is obvious. Attention should be paid to the radon in residential environment of geothermal field.