Moved into new (to us, built in 1980) house 2 years ago. Installed an Airthings radon meter a year ago. Levels get up to 400 Bq/m3 when all the windows are closed. Finally had a radon mitigation system installed. Will hopefully get to much safer level below 100 Bq/m3.


No, it depends on the geology. Some granitic rocks, black shales, sedimentary rocks with high concentrations of uranium, and metamorphic rocks derived from the latter 3 will have high radon. Otherwise it’s not a problem.
Odds are your local or national government has published radon susceptibility maps with detailed info.