## 3 Results and Discussion  
Indoor radon concentration values can vary on daily basis, depending on several factors: thermo-hygrometric conditions, time of season, soil types, strength of the radon source in the underlying bedrock, pressure changes created by the building as well as level of ventilation and occupancy itself also contribute significantly [6; 7; 8; 9; 10; 11]. Since indoor radon concentrations vary with diurnal and seasonal variations, we consider these when performing short-term radon measurements. In Figures 2-4, results were presented with 4 subplots to differentiate possible radon variations with temperature, humidity and air pressure. Furthermore, for the radon concentration values, arithmetic and geometric mean were shown. The arithmetic mean (AM) is the most common way of calculating an average. However, the geometric mean (GM) is a better measure of average radon data. The distribution of radon concentrations is asymmetrical around the average as can be seen from Figures 2-4. As a result of this asymmetry, the higher concentrations have a disproportionately greater weight than the lower ones in the calculation of the arithmetic mean. This problem is largely avoided by the geometric mean and, thus, this statistic is the one recommended generally by radon experts for estimating the average radon concentration in an area [1; 14]. The maximum (max) concentration is based on the single most extreme value in a distribution and the minimum (min) concentration is usually reported only for the zip code areas because it is always close to zero where there are large numbers of measurements [14]. Figure 2 shows radon concentration level in an office building (R1) in three different floors: basement storage (R1a), basement laboratory (R1b), office on 1 st (R1c) and 3 rd (R1d) floor. In the basement storage there was no ventilation as it is in the center of building with no windows. The laboratory in the basement was occasionally occupied with manual/passive ventilation through small windows. Office rooms (manual ventilation through windows) were mostly occupied during working hours (07:00-16:00). The occupancy of the office rooms during week working hours compared to weekend non-occupied rooms has an effect on radon concentration. In the building basement storage, higher radon concentrations were expected as the main source of radon is the soil since its generation and transportation through foundations in the basement are closely related to geology. The effect of a basement (R1a, R1b) on the radon levels in a building basement is two-fold: firstly, radon concentration on the floors above (R1c, R1d) a basement can be comparatively low as the rooms have no ground contact and, secondly, the ventilation is weaker in the basement compared to other floors. The effect of temperature, which was approximately constant in the basement (R1a, R1b) compared to the floors above (R1c and R1d), showed some comparable trends. This effect was most prominent in office rooms due to heating (natural in summer, heating in winter) compared to low-to-non heated rooms in the basement. A similar effect was observed for humidity and air pressure. A close correlation was observed between the hourly indoor radon variations with environmental parameters, temperature, humidity and air pressure indicating that indoor radon concentrations may be affected by both indoor-to-outdoor temperature, humidity and pressure differences [8; 15; 16]. Similar behavior was observed for samples shown in Figures 3 and 4 that presented radon measurement in the family house (R9, basement garage and kitchen storage) and in the wine cellar house (R6, basement storage room and dining storage room). For the family house (R9), day/night radon concentration variations were observed as well as indoor-to-outdoor temperature, humidity and pressure differences. The main radon effect in the family house was caused by the closed windows during the night, heating, occupancy in garage and in rooms.