B015 Background indoor radon

A methodology to determine the background radon level in Hong Kong

Brief:

Diluting the radon level in an enclosure with outdoor fresh air is commonly adopted for indoor environment. However, most of the fresh air intake position of the high-rise air-conditioned buildings in Hong Kong is typically located in the mechanical floor, where the outdoor fresh air might be pre-contaminated by the radon emitted from the building materials in mechanical floor. In this study, a one-year long-term measurement of the radon concentration, air temperature and relative humidity in an indoor space and the corresponding fresh air intake position was conducted to investigate the probable relationship of radon concentrations between indoor and fresh air intake position. The result provides a reasonably accurate estimation of the background radon concentration, and indicates the seasonal variation of radon concentration in different locations. It was found that there is a relationship between the air change rate and the indoor radon level. Hong Kong Environmental Protection Department (HKEPD) developed a guidance of the safe indoor radon level, the minimum fresh air quantity required can be determined with this guideline.

Further information:

Mui KW, Wong LT, 2004. A methodology to determine the background radon level in Hong Kong, Joint Symposium 2004: Servicing Dense Built Environment, CIBSE, Kowloon Shangri-La Hotel, 16 November, Hong Kong, pp. 143-153.