2017 No https://pubmed.ncbi.nlm.nih.gov/29036677/ Mullerova, Monika Europe Exposure Study Modeling Elementary (K-5) Radon The results show that radon concentration is less than 300 Bq m−3 in approximately 86.0% of cases in the first period and in 82.1% of cases in second period. However, rooms in kindergartens with radon concentration exceeding 1000 Bq m−3 were found in Slovakia.