Radon measurement in schools and kindergartens (Kremikovtsi municipality, Bulgaria

Indoor radon concentration was measured in all schools (n = 9) and kindergartens (n = 7) of Kremikovtsi district, Bulgaria, using passive integrating electret detectors. The study was based on two successive: short and long term set measurements. In first phase, the short term detectors were deployed in all frequently occupied rooms in ground floor. The exposure was during the summer vacation (2011) under close condition with 10 days duration. From the results of short term measurement we have found that the radon concentration in 4 schools and 5 kindergartens were above the recommended National level of 300 Bq m-3 for existing buildings. In order to confirm the initial shortterm measurement long-term measurements for the period from September 2011 to April 2012, in the same buildings of schools and kindergartens were performed under normal functional conditions (second phase). Comparing the results obtained from the short-term measurements under close conditions with the results of long-term measurement, we found that measured values were in correlation (R = 0.817)