Radon potential zoning

The mapping of soil radon potential areas has been established by IRSN (Institute for Radiation Protection and Nuclear Safety). It is at the municipal level in order to know the radon potential of its municipality. The capacity of the soil of his municipality to emit radon is the first of the three main factors that make it possible to apprehend the radon risk in a building. This zoning of the territory takes into account the richness of uranium and radium present in the rocks of the subsoil, the porosity of the soil as well as several particular geological factors that can promote the rise of radon to the surface such as faults, underground cavities, mining areas ... This zoning has led to classify the municipalities in 3 categories: Category 1: Category 1 radon potential municipalities are those located on geological formations with the lowest uranium content. On these formations, a majority of buildings have low radon levels. Category 2: Category 2 radon potential municipalities are those located on geological formations with low uranium levels but on which specific geological factors (failures, karsts, mines, etc.) can facilitate the transfer of radon to buildings. These particular geological conditions may locally facilitate the transport of radon from the rock to the soil surface. As a result, some buildings may have high radon levels. Category 3: Category 3 radon-potential municipalities are those which, on at least part of their area, have geological formations whose uranium content is estimated to be higher. On these formations richer in uranium, the proportion of buildings with a high level of radon is higher than on the rest of the territory.