Comparison of retrospective and contemporary indoor radon measurements in a high-radon area of Serbia

In Niška Banja, a comparison was made between two retrospective radon measuringmethods and contemporary radon measurements. The two retrospective methods derive the radon concentrations that occurred in dwellings over longer periods in the past, based on the amount of 210Po on the surface of glass objects (surface traps, ST) or in the bulk of porous materials (volume traps, VT). Both surface implanted 210Po in glass objects and contemporary radon in air were measured in 46 rooms, distributed in 32 houses of this radon spa-town, using a dual alpha track detector configuration (CR-39 and LR115) and CR-39 track etched detectors, respectively. In addition to the use of surface trap measurements, in 18 rooms (distributed in 15 houses) VTsamples of suitable material were also collected, allowing to compare ST and VT retrospective radon concentration estimates. For each room, contemporary annual radon concentrations (CONT)weremeasured or estimated using seasonal correction factors. Geometric means (GM) are similar, ranging from1040 to 1380 Bqm−3,whereas geometric standard deviations (GSD) for both the retrospectivemethods are greater than for the CONTmethod, showing reasonable agreement betweenVT, STand CONTmeasurements. Regression analysis, shows that for VT–ST the correlation coefficient r is 0.85, for VT–CONT r is 0.82 and for ST–CONT r is 0.73.