Notes: Standard for indoor environmental pollution control of civil building engineering (GB50325-2020) requires that radon concentration in soil and radon exhalation be measured in engineering investigation and design stage. If radon in soil is between 20 000-30 000 Bq/m3 or surface soil radon exhalation is more than 0.05 Bq/(m2.s) preventive measures should be taken to ground. Furthermore, there is a limit on radionuclide in building materials (GB 6566-2001).