Abstract: Three sets of newly-built house in Guangzhou were selected to view the relationship between indoor radon activity concentrations and the air change rate. Indoor radon activity concentrations and the air change rate were measured when rooms were in the following three conditions: fully enclosed; air hole opened; both the air hole and the window opened. The indoor radon activity concentrations in the rooms of the same floor and in the rooms of the same side but different floors were measured using activated carbon box method. The results showed that, inside the bedroom of a totally enclosed new house in Guangzhou, the air change rate was low (less than 0.2 h^-1), and the indoor radon activity concentration was high (more than 200 Bq/m³). At the air change rate of around 0.5 h^-1, the indoor radon activity concentration dropped below 200 Bq/m³; and a significant reduction in the radon activity concentration below 100 Bq/m³ was found at the air change rate above 1.0 h^-1. Indoor radon activity concentrations decreased vertically with the increase of floor level. No obvious horizontal trend on indoor radon activity concentration was found for the same floor.

Key words: newly-built house, indoor radon activity concentration, air change rate