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„It is wrong to think that the task of physics is to find out how nature is. Physics concerns what we can say about nature.“ (Niels Bohr: „Atomic Theory and the Description of Nature“, 1931)


For many years IAF has been a highly competent and experienced service provider in the field of radon measurement and mitigation. IAF is an Approved Body for radon measurements according to Art. 155 of the German Radiation Protection Ordinance and accredited for the measurement of indoor radon concentration under ISO 17025. IAF helps authorities, business and private clients comply with legal requirements, by measuring radon in buildings (including radon at workplaces), measuring radon thightness of building materials such as liners and coatings, and by determining radioactivity in building materials and aggregates.

Services offered by IAF (selection)

Ingress of radon, a very mobile noble gas, into buildings and its subsequent dispersion within the building is a complex process that requires experience in planning, execution and evaluation of measurements including an understanding of all relevant physical processes. Based on many years of involvement in research and development projects and dozens of site investigations, we can offer the following services:

  • Short and long term measurement of radon and progeny, potential alpha energy concentration, equilibrium factor
  • Time-correlated measurements in multiple rooms to investigate the dynamics of radon concentration, radon ingress points, convective processes and air flowpaths. IAF can deploy more than 20 radon monitors for a single measurement campain, providing an unparalleled amount of information that can be assessed by our experts
  • Determination of the radon potential of soil and foundation rock using in-situ measurements (determination of the radon concentration in soil and its gas permeability), which is required for the planning of newbuilds and extensions of existing buildings
  • Technical reports on the radon situation in private homes and public buildings (schools, office buildings, hospitals etc.), and development of site-specific recommendations for radon-safe construction
  • Quantification of radon release (emanation and exhalation rates) from building materials, as well as from mining, mineral processing and other wastes
  • Determination of the radon diffusion coefficients and calculation of the radon diffusion length of building materials and components (proofing of buildings, cable sleeves, basements, floor screed, wall insulation etc.)
  • Radon tightness tests during construction, „Blower Door“ tests according to DIN EN 13829 to assess the radon tightness of buildings
  • Measurement and evaluation of the radon situation in geothermal installations, water utilities, etc.
  • Determination of radon in drinking water. IAF provides radon-proof containers to customers if required.

Apart from „conventional“ radon (Rn-222) of the U-238 decay series, IAF can measure the relatively short-lived Rn-220, or thoron, from the Th-232 decay series, of course.

IAF employs certified „Radon Experts“ according to regulatory provisions in Saxony.

Significance of average and time-dependent radon concentration

Long-term measurements over several weeks or months (typically using passive nuclear track etching detectors) provides an average value of the radon concentration and thus a first impression of the radon situation. However, the radon concentration is usually subject to significant circadian and seasonal fluctuations, often over several orders of magnitude. Peak values of the indoor radon concentration occur typically in periods during which the building is not used, and vice versa. This can be seen from the diagram below. Calculating the radon exposure and effective dose due to radon from average concentrations leads often to an over-estimation of the indoor dose.


A more realistic estimate of the exposure to radon and its progeny requires time-resolved measurements of the radon concentration. Over many years IAF has accumulated experience and know-how in planning, execution and evaluation of time-resolved (dynamic) measurements and operates a large park of radon measurement devices.

In addition to the radon concentration, airflow and radon dynamics in a building require knowledge of the air pressure (pressure differentials) and temperatur, that are measured simultaneously as part of every campaign.


Measurements of time-dependent radon concentrations in different rooms of a building, together with pressure and temperature measurements, is a precondition for the planning and implementation of radon mitigation measures so that current and future regulatory limits on indoor radon concentration can be complied with. An example of a complex measurement of indoor radon on different floors, to calculate the convective transport of radon, is shown in the diagram below.


IAF has developed comprehensive internal SOPs and guidelines for radon measurements and monitoring programs, so that our results are of highest quality and reliability. For example, this relates to the following aspects the importance of which is often underestimated:

  • Selection of the right detectors and measurement devices, periodic maintenance and calibration
  • Correct positioning of the Rn detectors in a room or building
  • Parallel determination of other radiological and non-radiological parameters in order to properly assess and interpret the radon data
  • Recording and documentation of the environment of the measurement and its results.

IAF is a founding member of the European NORM Association (ENA) incorporating the European ALARA Network for NORM EANNORM and collaborates closely with the European Radon Association (ERA) and NORM4Building. This ensures a continuous exchange of professional experience and keeps IAF abreast of international developments and best available techniques (BAT).

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