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Soil gas measurement of the radon risk in building projects

Soil gas measurements are used to assess the radon availability in the soil as the most frequent cause for increased concentrations in buildings to be erected. By using this analysis suitable prevention measures can be made already before beginning of the construction. As a standard procedure probes will be driven into the soil through which the soil gas will be drawn in.

The soil gas will be generally loaded by high radon and thoron concentrations (10,000 to 1 Mio Bequerel per cubic meter). Due to its short half-life period, thoron cannot penetrate from the soil into the building what requires a separate measurement of radon and thoron. Many measuring points should be measured within short time requiring a fast response and damping of the measured signal. Finally, the high soil gas concentrations will result in a permanent activation of the measuring chamber by the long-lived radon daughter Po-210. The thoron daughter Pb-212 having a half-life period of more than 10 hours will also activate the measuring chamber that would endure for several days.

For this reason, only monitors with a real alpha-spectroscopy (semiconductor detectors) are suitable for fast soil gas measurements by means of which the individual isotopes can be measured separately from each other. By the separate analysis of the direct decay products you can perform a minimum response and damping time. Those isotopes as followed in the decay chain and that activate the measuring chamber are not a part of the measurement. Consequently, there will be no contamination of the monitor. Furthermore, the device should be equipped with a pump that would reliably draw in the soil gas in an easy way. But, of course, a small light-weight and robust device offers advantages for the field operations.

The instrument RTM 1688-2 meets all these requirements and is especially suitable for this application. As an option a protection kit against the penetration of water during soil gas sampling is available.

In addition to the features of RTM 1688-2, the RTM 2200 comes with a convenient soil gas measuerement cycle and offers options for a GSM receiver and soil permeability measurements.