For new constructions, it can be valuable knowing if the soil the building will stand on is classed as high risk soil from a radon perspective, as radon protection can be built in from the start. In some cases, the municipality’s local planning committee demand a survey of radon levels in the ground before granting a building permit.

We recommend three soil radon detectors for testing a single house location.

Measuring with ground radon detectors

Eurofins’ ground radon detectors are buried in the ground at approx. 1 m depth. A 75 mm PVC tube which can be driven down into the ground can be used. If digging by hand, make a pyramid-shaped hole as in the image. The detector is opened and placed in the hole/tube. It is important that no air enters from open air, as you want to measure the soil air in order to get a value for soil radon. Measuring must span over approx. 5 days, after which you retrieve the detector and close it. The detector is then sent in the to the laboratory. Measuring for longer than the recommended time does not give better results, but can make the reading operation more difficult. It is important that the test sample is returned immediately after measuring is completed. Radon (222Rn) has a half-life of 3.8 days, and if decay continues over a longer period, it becomes more difficult to calculate what the ground radon level is.

At the laboratory, we measure the emitted gamma radiation from the two isotopes of radon daughters, Bismuth (214Bi) and Lead (214Pb). Based on the amount of gamma radiation, we can back calculate the level of soil radon.

The detector will also capture thoron (220Rn); since this has a short half-life of 55.6 s, all the thoron will have decayed before the detector arrives to the laboratorie and therefore does not affect measuring. Thoron levels are not dangerous to humans and there is no legislation either on thoron.

Do not measure ground radon

  • If the topsoil is thin. If you do not have at least 0.7 m of topsoil, the soil gas will be affected by wind and pressure. You do not get a representable value.
  • If you come down to rock. Instead a gamma measurement of the rock must then be performed.
  • If there is ground frost, measurements becomes very unreliable.
  • If water is present in the hole/pit. Water prevents the detector from capturing radon.
  • If you have bored through asphalt. The asphalt acts like a cap, and the levels in the hole will not correspond to the true values.