Comparison with published data used to derive an average indoor radon : soil 226Ra ratio shows that
whereas the published data are generally clustered with no obvious correlation, the data from this
study have substantially different relationships depending largely on the permeability of the
underlying geology. Models for the relatively impermeable geological units plot parallel to the
average indoor radon : soil 226Ra model but with lower indoor radon : soil 226Ra ratios, whilst the
models for the permeable geological units plot parallel to the average indoor radon : soil 226Ra model
but with higher than average indoor radon : soil 226Ra ratios.