Evaluation of several air cleaners for reducing indoor radon progeny

Abstract

Over the past several years, studies have been made of the effectiveness of several kinds of air cleaners in removing radon decay products from indoor air using a recently developed automated, semi-continuous measurement system that can determine the activity-weighted size distributions in occupied homes. Measurements of activity-weighted size distributions and radon concentrations were made every 90 min in a home with a high air exchange rate. A week-long series of measurements was made for the home with no cleaner operating and a similar set of measurements were made for each of the air cleaners. Two different types of air cleaners were tested in this study; filtration units (two different designs from two different manufacturers) and two ion generator/fan systems (identical design NO-RAD systems, but from two different manufacturers). From the measured distributions and a dosimetric model, the effect of the air cleaners on the dose to lung can be estimated. It was found that the filtration units resulted in a median reduction in exposure of 15% and 36% for the two units and corresponding dose reductions of 32% and 53%. The two NO-RAD systems produced 37% and 10% reductions in the median exposure, but the reductions in the median dose were 49% and 46%. Examination of the components of the NO-RAD system operating separately resulted in the fan causing a small dose reduction and the ionizer producing a small dose increase. However, very few size distributions were measured for these separate component studies and a more detailed study of the separate effects of the NO-RAD components is needed.