Transfer factors for assessment of soil gas radon concentrations and indoor radon activity concentrations

For Germany, the regional distribution of soil gas radon is now well known. An approach combining specific information from geological field research and indoor measurements was developed as a method to predict the proportion of houses exceeding a certain indoor radon concentration. For improvement of the outlined method, the Federal Office of Radiation Protection has launched the research projects St.Sch 4186 and 4187 to elaborate empirical transfer factors for the estimation of radon contamination of houses in the Federal Republic of Germany. In 1 229 exactly located dwellings, one-year-measurements of indoor radon were performed and comprehensive specifications to the properties of the houses were reported by the occupants in a comprehensive questionnaire. For statistical evaluations of the correlation between soil gas radon measurements near houses and corresponding long-time indoor measurements in a spot-to-spot assignment, approximately 1 303 soil gas measuring sites were selected to sample the relevant geological units. The aim was to obtain a set of transfer factors for different radon relevant properties of houses e.g. constructing type, age, foundation and other site and building specifications, and to derive a nation-wide prognosis map on the basis of administrative districts. (orig.)