Thorough investigations on indoor radon in Băiţa radon-prone area (Romania)

A comprehensive radon survey has been carried out in Băiţa radon-prone area, Transylvania, Romania, in 4 localities (Băiţa, Nucet, Fînaţe, and Cîmpani) situated in the vicinity of former Romanian uranium mines. Indoor radon concentrations have been measured in 1128 ground floor rooms and cellars of 303 family houses by using CR-39 diffusion type radon detectors. The annual average of indoor radon concentration for Băiţa area was found to be 241±178Bqm−3, which is about two times higher than the average value of 126Bqm−3, computed for Romania. About 28% of investigated houses exceed the reference level of radon gas in dwellings of 300Bqm−3. The indoor radon measurements on each house have been carried out in several rooms simultaneously with the aim of obtaining a more detailed picture on the exposure to radon in the studied area. An analysis on the variability of radon levels among floors (floor-to-floor variation) and rooms (room-to-room variation) and also the influence of factors like the presence of cellar or the age of the building is presented. The coefficient of variation (CV) within ground floor rooms of the same house (room-to-room variation) ranged between 0.9 and 120.8%, with an arithmetic mean of 46.2%, a large variability among rooms within surveyed dwellings being clearly identified. The mean radon concentration in bedrooms without cellar was higher than in bedrooms above the cellar, the difference being statistically significant (t test, one tail, p0.05). ► The annual average of indoor radon concentration for Băiţa area was 241±178Bqm−3. ► A large variability among rooms within surveyed dwellings was clearly evidenced. ► The radon concentrations in bedrooms without cellar were higher than above the cellar. ► The ratio between radon concentration at ground floor and cellar was calculated. ► A wide variation range between ground floor rooms and cellar was reported.