Indoor radon levels in Hungarian kindergartens

Annual average indoor radon activity concentration was studied in 88 Hungarian kindergartens in 76 towns of 10 different counties. Annual average indoor radon activity concentration in the kindergartens was 61 Bq m − 3 , maximum was 160 Bq m − 3 . In the kindergartens the seasonal variation of radon is not so strong like in dwellings, because of the permanent ventilation and the closed period during the summer break.