Room experiments were conducted to investigate the effects of an air cleaner on radon mitigation. Radon concentration, equilibrium
equivalent radon concentration and unattached fraction were measured during the experiments. Two types of filtration were
tested using the air cleaner which has a high efficiency particulate air filter (HEPA-filter) and a deodorizing activated
carbon (carbon-filter). One is the filtration with the HEPA-filter plus carbon-filter and the other is the filtration with
only the HEPA-filter. The effective doses from radon progeny were significantly decreased. Both filtration methods were effective
for the mitigation of effective dose due to radon progeny.