The study on effects of indoor air filtration on radon exposure to residents

Objective: To evaluate the influence of indoor air filtration by air purifier on the behavior of indoor radon progeny and estimate its effects on indoor radon exposure to residents. Methods: The concentrations of indoor radon progeny with and without the air filtration were calculated by the theoretical model developed in this study. Based on the dose conversion factors of attached and unattached radon progeny, the mitigation effects of indoor radon exposure due to the air filtration were estimated. Verification experiments were conducted in an airtight room. Results: With the air filtration rate increased, the removal efficiency of indoor radon progeny would appear more obvious. For an airtight room with its initial aerosol concentration of 10000 cm^-3, the concentration of total radon progeny would decrease by more than 90% when the air filtration rate exceeded 10 h^-1. But the concentrations of indoor unattached radon progeny would increase by using the air purifier in different extents. The variations of radon progeny concentrations and the decrease of internal doses were closely related to the filtration rate of air purifier. With the air filtration rates increased, the mitigation effects would be better and faster. The internal dose would reduce by more than 70% when the filtration rate exceeded 5 h^-1. Conclusions: Although the indoor concentration of unattached radon progeny will increase by using the air purifier, it is still effective in reducing the exposure dose to residents due to the inhalation of radon progeny. (authors)