^rn Progeny Surface Deposition

The radiological hazard of radon gas to occupants in residential environments is from the particulate progeny "'Po, ""Pb, ^Bi and "4P0, rather than ^Rn itself. Attachment to aerosols, plateout and resuspension impacts on the actual progeny airborne concentrations. Plateout rate factors are measured for different air change (ventilation) rates, ACH, in a 0.28 m3 test chamber for interior residential materials. Wallboard, hardwood (varnished), carpet, drapery, glass, ceiling tile, and concrete were used for plateout measurements. A NIST-calibrated " ' ~ a source was used to assure constant source emanation rates (within * 1% S.D.). ACH varied from 0 to 1.0 h"' in a total of 32 plateout measurements. All measurements were made in a continuous air conditioned interior environment maintaining temperature at 22.2  1 . lo C and relative humidity of 30% * 10%. The ACH was controlled to  1 .O% S.D. The overall accuracy of the plateout rate values is estimated to be  15% S.D. For the different materials, the plateout rates for '"Po progeny varied by nearly a factor of six. Drapery was found to provide the largest plateout rates. Computations were made of equivalent plateout rates and equilibrium fractions for a standard 5m x 5m x 3m high room to provide values to compare with other work. Resuspension rate factors, R, are measured and reported for five interior residential materials (carpet, drapery, glass, wallboard and hardwood). A new time-dependent measurement method was used to identify a small difference in buildup rate of '^Po to equilibrium from the presence of resuspension and a fit was performed on the data to determine the value of R that provided the best fit. Values for R obtained for carpet, drapery, glass, wallboard and hardwood were 0.55,0.44, 0.36, 0.29 and 0.31, respectively (* 30% S.D.).