Radon measurements in kindergartens in area affected by underground mining

A survey of radon concentration in kindergartens in area of town Piekary ?l?skie, affected byunderground mining, have been performed. Measurements were done in cellars and classrooms on thegroundfloor. The highest value of radon concentration in the classroom during long-term monitoringwas of about 228 Bq/m3. During the survey we proved a correlation between concentrations of radonin soil gas and in buildings. Easy migration of radon from soil into buildings enables a specificgeological structure of the bedrock, location of particular kindergartens over active mines and due tothat fact that a lot of fissures and cracks in walls of buildings are caused by coal mining underneath thetown.