Radon exposure in buildings

Radon, the daughter nuclide of radium, develops at any place where its mother nuclide is present. The radon concentration in buildings may reach some kBq/m 3 . Normal ranges of the indoor radon concentration have been defined in a number of countries. Radon concentrations up to 250 Bq/m 3 are regarded as normal in Germany. This is a recommendation level. The most important source of radon in buildings is the geological ground. Other sources are building materials, mining residues such as shallow drivings, and, in some cases, radon dissolved in water, mineral oil, and gas.