Seasonal variation of radon concentration - measurements in some european countries

The radon concentrations in indoor air and in soil air vary both on short term (daily, weekly) and onlong term (seasonal). The radon level and its changes depend on a few parameters, which may bedifferent from one building to another and from one type of soil to another. It is important to know theseasonal variation of the indoor radon levels if the level is to be compared with the national upperlimits in Europe for indoor radon concentrations. Also, the seasonal soil radon variation is important toknow, especially if building regulations include demands on protection against entrance of soil radoninto new constructed buildings.The result of measurements of indoor radon and soil radon concentrations are discussed in the report.The measurements are made in and at houses, which are selected for long time studies of radon levelsindoors and in the soil surrounding the houses. The houses are situated in countries in Europe withvery different climate, building tradition and living habits of the inhabitants. The report emphasizes onthe seasonal variation in the different countries of the radon concentrations both indoors and in theground.It is found that in countries with cold climate the indoor radon concentrations rise in the winter if thesoil is the main source and the indoor concentrations are over 100 Bq/m3. It is also fond that the radonlevels in a house may be very individual from one time to another as a consequence of the habits ofthe inhabitants.Concerning soil radon, studied in the investigation, the seasonal variation does not show any generalpattern. There is however a tendency of a variation of a factor of two or more during the year of thesoil radon concentration in a measuring point in the garden.