The Radon Diffusion Length as a Criterion for the Radon Tightness

INTRODUCTION The rising public wish for natural residing, new rules for energy and resource saving construction and the interest of the industry on inexpensive raw materials lead to new developments in the field of building materials. In this connection, the isolation of buildings against radon, especially in radon prone areas, shows an inclining interest. A recent German case control study on indoor radon (1) as well as extrapolation of data from uranium underground miners (2) suggest a relevant contribution of indoor radon to the lung cancer risk in the general population. Higher radon concentrations indoors usually depend on the possibility, that radon can penetrate from the surrounding soil. In most cases, the intrinsic radon exhalation of the materials can be neglected (3). We measure routinely building and isolation materials to determine the diffusion coefficient and decide, whether the materials are radon tight or not. Naturally, the tightness of the material depends on its, so we use the diffusion length, respectively the dimensionless quotient between the diffusion length and the thickness as a criterion.