The Ardennes is a strongly radon-affected area with more than 10% and up to 40% of the houses above 400 Bq/m3. It covers about 5000 km² and includes 32 municipalities with a relatively low population density (~76 people/km²).
From the geological point of view, the Ardennes is mainly characterised by Lower Paleozoic rocks, composed of Cambrian and Ordovician shales and quartzite, Lower Devonian slate and schist and limited Quaternary deposits and alluvial cover.
The Ardenne massif is intensely folded and fractures, making its surficial parts relatively permeable and hence radon prone.
A data set including soil-gas and permeability measurements on an 1x1 km grid is available for the RESPIRE project. About 5000 indoor radon measurements are available too.