| Abstract: | Radioactive noble gas radon (222Rn) is one of the most important indoor air pollutants world-wide, and a long term exposure to radon may result into lung cancer. The aim of the master's thesis was to evaluate how the living habits (especially ventilation of rooms) affect indoor radon activity concentrations and consequently the effective doses received by residents. In the Idrija town, two houses (H1 and H2) were chosen, located near the Idrija's fault, in order to compare the dynamics of radon in relation to living habits of residents. First, in both houses air samples were taken with ɑ-scintillation cells in several rooms (living room, kitchen, bathroom, bedroom, room/corridor) and instantaneous radon activity concentrations determined. Based on these results, two rooms, one in each house, with similar radon levels and similar use were selected for further research. They were the bedrooms, where the radon activity concentration differing for 1 % only, and where radon was monitored continuously (once an hour) from January 1 to November 18, 2018. From hourly radon activity concentrations, various concentration averages have been calculated: annual, daily, winter, spring, summer and autumn. These averages have been then used to calculate effective doses received by a resident when sleeping (8 of 24 hours for whole year). In both bedrooms, only the summer average did not exceed the 300 Bq m─3 limit. As expected, the highest radon levels have been observed in winter, the lowest in summer, and medium in spring and autumn, being similar in both rooms. Hourly radon levels were higher in night-time than daytime, being the highest in the morning, just before the aeration of the rooms was started. The annual average radon activity concentration was 797754 Bq m─3 in H1 and 854785 Bq m─3 in H2. The annual average effective doses have been calculated in two ways, based on radon activity concentration (i) for whole day (0─24h) and (ii) for night-time (22─6h) only. The annual whole day (0─24h) effective dose received in bedroom of H1 was 8.83 mSv, and of H2 9.52 mSv, respectively. The annual doses, based on night-time radon concentrations (22─6h), were for a factor 1.03 in H1 and 1.07 in H2 higher, respectively. Effective doses are strongly correlated to aeration of bedrooms; they significantly decreased with increased aeration. The effective dose, on the basis of night-time radon concentration (22─6h), is in the bedroom H1 4.7 fold lower in summer than in winter and in the bedroom H2 5.1 fold, respectively. |
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