Characterization of 222Rn entry into a basement structure surrounded by low-permeability soil

An experimental facility has been developed to monitor the entry rate and concentration of 222 Rn in a basement-type structure surrounded by soil having a permeability on the order of 10 -11 m 2 . A data acquisition system recorded environmental conditions outside and inside the structures, plus basement air exchange rate information, every 15 min. Indoor 222 Rn concentrations ranged from 400 to 1,400 Bq m -3 . The observed 222 Rn entry rate is highly variable and has two primary components; a constant input rate caused by diffusion of 222 Rn through the concrete walls and floor, and a variable rate that depends upon indoor-soil pressure differentials of only a few pascals