Methodology for determination of Radon soil concentration - Bertin Instruments

    Monitoring Radon in homes and workplaces

    Methodology for determination of Radon soil concentration

    Julien Villert


    The radioactive gas radon is estimated to cause about 21,000 lung cancer deaths per year in the U.S., according to the Environmental Protection Agency’s (EPA) 2003 Assessment of Risks from Radon in Homes. It represents the second largest cause of lung cancer in the world. Underground workplaces such as basements, mines, caves and utility shafts can have significant levels of Radon as well as above ground workplaces in Radon affected areas. In the U.S., new homes are not required to meet a specified radon level. While radon problems may be more common in some areas, any location may be affected. The only way to know about is to test. Understanding the potential radon levels allows proper systems installation during construction versus after construction vent system.

    Soil testing methods

    Currently, the EPA does not recommend soil testing to determine whether a house should be built radon resistant. However, several new projects have provided a better understanding of factors that influence measurement results.

    a) The soil-gas concentration can vary, often greatly, over a small distance. A significant variation often indicates the presence of faults or tectonic zones.
    b) The sampling depth influences results when backfill may have been utilized
    c) Soil permeability is highly variable and related to the degree of weathering, porosity and moisture content.

    Measuring at the sufficient depth the activity concentration of the radon soil gas, the nature of the soil and the atmospheric conditions can provide key information in designing radon reduction method for an energy efficient home.

    With the AlphaGUARD, Bertin Instruments offers different ways to monitor radon in soil with several accessories:

    Conventional soil gas analysis with a soil gas probe

    • Easy and safe sampling thanks to the rilling tip, the insertable capillary probe and the aqua-stop filter.
    • One measurement point: approx.15 min.
    • Inflatable bag (packer) for airtight measurements when using existing drill holes
    • Extension set up to 10 m

    Radon Exhalation Measurements with a radon box

    Fig.1 AlphaGUARD hanging within the Radon-Box and operating in diffusion mode


    Fig.2 AlphaGUARD operating outside the Radon-Box in flow-through mode


    • AlphaGUARD can either hang within the Radon-Box and operate in diffusion mode or operate outside the Radon-Box in flow-through mode.
    • Char coal method also possible
    • Attachment area: 0,21m²
    • Inner volume: 0,035m³

    Multiple radon measurements with the valve selector box

    • The Valve Selector Unit is a module for timer regulated switching between up to five gas entrances.
    • Simultaneous radon concentration monitoring up to five different environments.
    • Successive measurement steps in repeating manner.

    Evaluation of the soil permeability with a differential pressure sensor

    The Differential Pressure Sensor – DSP 5000 – allows to draw conclusions of the prevalent soil permeability at the site and hence to describe the specific spot by the radiological variable “disposable radon”.


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