Industrial radon measurement guideline to get an overall view of the radon concentration in a workplace IRMA 0791-30

Open the Guideline as PDF.

General measurement requirements:

  • The measurements should be performed as long-term measurements meaning a measurement period of at least three months.
  • The measurements should be analyzed by a laboratory which is accredited to the ISO 17025 or NELAC standards.

Rooms/areas considered for measurement:

  • Rooms/areas which are occupied on a regular basis for more than 4 hours a day.
  • All underground/basement rooms/areas and other rooms, where there is a significant risk of major radon entry, which could be used by individuals for more than 50 hours per year (about one hour per week).

Number of detectors to use:

  • Basement and ground floor: Measure in all rooms/areas which fulfill the criteria above. For larger rooms and spaces, place at least on detector per 150 m².
  • On higher floors: At least two detectors per floor and at least one detector per 250 m².


  • A pre-study, to identify possible places where radon from the soil could leak into the building from below, should be performed before the actual measurement starts. In this pre-study, an understanding of pipe penetrations through the floor, ventilation and where any natural gamma radiation from building material is occurring should be identified to enable a more detailed plan to be made for the placement of detectors.
  • Since employees usually get a higher radon exposure in their homes, it is recommended that employees are offered radon measurement in their dwellings in parallel with those being made in their workplace.
  • Information about radon and the planned measurements should be distributed before the workplace measurements start.
  • Measurements should be performed during the building heating season and with a measurement period which fulfills national requirements.
  • The placement of the detectors within the rooms should follow national recommendations (actually quite similar from country to country).
  • Detectors should be placed in a secure way. Meaning that detectors should be sealed units that can be fixed and attached in such a way that any tampering or move during the exposure period can be clearly established and results invalidated.
  • Information concerning the amount of usage of a room/area may need to be logged, particularly basement areas that are infrequently occupied.

The Intention of this document

The intention of this document is to present an industrial guideline for radon measurement in workplaces. The purpose of the guideline is to establish good practice in measurement projects managed by radon consultants/companies where consultancy costs and time constraints (such as hours spent and travel expenses) for completing the project are of importance. In these cases, it may well be financially advantageous for the consultant/company to avoid returning to perform additional measurements. Therefore, to get a good overview of the overall radon concentration in the workplace, it will be extremely important to employ sufficient detectors at the very beginning of the investigation. This guideline only considers the first part of a measurement project. If elevated levels are found then follow-up measurements should be considered to check the radon levels during working hours in addition to recording, as accurately as possible, the exposure time.

When making this guideline, consideration has been given to existing measurement protocols and standards with a view to encompassing all the various regulatory requirements within one ‘best practice guide’. In particular, special consideration has been given to the requirements found in the US ANSI/AARST standard, the ISO 11665-8:2012 standard and specific national measurement protocols in different European countries.

There is an assumption in the guideline, that due to a variety of reasons, both accidental and sometimes malicious, circa 20 % of placed detectors will not be returned for analysis.