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Measuring radon before constructing a building – According to Czech legislation, anyone who wants to build a new house with habitable rooms must measure the radon index of the building site. The radon measurement protocol is one of the documents required by the Building Authority before a building permit is issued. The radon index of the building site is measured directly on site in accordance with the stateapproved methodology. This is based on measuring the radon concentration in the soil gas at a depth of 80 cm below the surface and measuring or assessing the soil permeability (Fig. 1).
Measuring radon indoors – Radon must be measured in habitable rooms, e.g. kitchens, living rooms and bedrooms, preferably when the house is inhabited. The measurements should be taken for a minimum period of one week. The real situation is much better described by a one-year average, because radon concentrations vary considerably in the course of a year. Various types of radon detectors are shown in Fig. 2 and Fig. 3. A one-week measurement is recommended as a control measurement of the quality of the operation of the building directly after the house is completed. Radon measurement in existing houses is recommended after the following types of house reconstruction: window replacement, additional application of external thermal insulation, replacement of floor structures resting on the soil, etc.

Fig. 1 - Scheme describing principles of measurement of the radon concentration in the soil gas.

Fig. 2 - Electret detectors (a) with the reader (b) are used for one-week measurement of indoor radon concentrations. RamaRn detectors (c) are convenient for longer durations of the measurement - from 2 months up to one year.

Fig. 3 - Monitor for continuous measurement (a) enables to evaluate time courses of the indoor radon concentration (b).