Abstract
An indoor radon survey has been carried in 120 schools situated in four districts of the Punjab province, namely Attock, Chakwal, Jhelum, and Rawalpindi. In each season, a total of 360 CR-39-based radon detectors were installed in the selected schools. After exposure the detectors were etched in 6M NaOH at 80 degrees C solution for 16 h and tracks densities, which are related to the radon concentration, were measured. Indoor radon concentration varied from 18 +/- 7 to 168 +/- 5 Bq.m(-3) with an average value of 52 +/- 9 Bq.m(-3). High indoor radon concentration values were found in the summer season, whereas lower values were recorded in autumn season. The mean annual radon effective dose equivalent was estimated to be 0.49 mSv per year. Present indoor radon concentration values are higher than that of the world average value of 40 Bq.m(-3), but lower than the action level recommended by the ICRP.