Estimation of the radon surface exhalation rate from a wall as related to that from its building material sample

The calculated radon areal exhalation rate from a wall, based on the one-dimensional diffusion description by Fick's law, is found to be different from that calculated from a building material sample based on the three-dimensional description. This paper is aimed to analytically clarify the origin of this difference and to relate the rates to each other. This allows finding the radon areal exhalation rate from a wall if that from the constructing building material sample is known. More importantly, it gives a more accurate estimation for the radon areal exhalation rate from a wall, which is required to calculate the indoor radon concentration, and accordingly to calculate the radon inhalation doses.