Radon transport in soil and its relation to indoor radioactivity

The transport of radon from soil to the indoor living space involves diffusion and viscous flow in the soil coupled with transfer to the building interior of radon-rich air which accumulates in cavities and channels below and around the foundations of buildings. Radon concentrations in soil pores at depth are dependent upon the radium content of the soil, emanating power for radium, and soil moisture content. Atmospheric pressure fluctuation, thermal gradients in fractured rocks, and air instabilities due to temperature differences allow air of high radon content to reach living space in dwellings in addition to that which comes directly from building materials and other sources.