Efficacy of air cleaning systems in controlling indoor radon decay products

Field evaluations of an air filtration system and an electronic air cleaner to remove Rn decay products were performed in a single-family house located in the Northford, CT area. Field measurements included the Rn concentration, particle number concentration, and concentration and activity size distribution of Rn decay products. A semi-continuous screen diffusion battery system with six parallel sampler/detector units was used to determine the concentrations and size distributions of the Rn decay products. Indoor particles were generated by common activities such as vacuuming, washing and drying clothes, opening the outside door, and cooking. Influences on the size distributions over the size range from 0.5 nm to 500 nm of Rn decay products were investigated in the domestic environment. The effect of the air cleaners was to decrease the concentration of the decay products and to reduce the equilibrium fraction. For the filtration system in particular, the activity fractions in the smallest size range were increased. However, the overall effect of the air cleaners was to reduce the median dose. The filtration unit was found to be more effective than the electronic air cleaner.