RESUMO
The construction department of the Chinese government is now discussing the possibility of reducing indoor radon exposure through controlling the radon exhalation rate of building materials. However, which quantity is suitable for control and how to specify and measure this quantity are still not clear. A comparison of a theoretical model and measurement process of radon exhalation between the surface of soil and building materials was carried out. As a result, the so-called intrinsic exhalation rate is thought to be a suitable quantity for control. Through theoretical analysis and experimental comparisons of different pre-treatment methods, it was indicated that the closed chamber method could be used to measure the intrinsic exhalation rate of building materials. Measurement results show that the average intrinsic radon exhalation rate of building materials commonly used in Beijing is 4.891 mBq m(-2) s(-1), with a range of 0.323-21.250 mBq m(-2) s(-1), and the average diffusion length is 16.448 cm, with a range of 2.371-41.960 cm.