Reference levels and regulations concerning radon in dwellings

According to the Ministry of Social Affairs and Health’s Decree on Ionizing Radiation, the reference level for the radon concentration in indoor air in dwellings and other living areas is 300 becquerels per cubic metre (Bq/m3) of air. Questions about radon concentrations in dwellings are answered by the municipality's health protection.

Radon concentration is determined as the annual average radon concentration measured over a continuous period of one year or estimated from a shorter measurement. The measurement must be continuous, must last at least two months, preferably three, and must be conducted between the beginning of September and the end of May.

In designing and constructing new buildings, the reference level for the radon concentration in indoor air is 200 Bq/m3. If the reference level is exceeded, the building owner can require the builder to make repairs to reduce radon levels.

The radon concentrations stated in the result report received from the laboratory that conducted the radon measurements are averages of the concentrations that prevailed during measurement. The reference levels 200 and 300 Bq/m3 refer to the annual average radon concentration. The annual average radon concentration is calculated by multiplying the result measured during the radon measurement period (1 September–31 May) by 0.9.  Accurate determination of the annual average radon concentration requires a 12-month measurement.

Regulations and guidelines concerning radon-safe construction work

  • Decree of the Ministry of the Environment on Foundation Structures, 465/2014.
  • Decree of the Ministry of the Environment on Indoor Climate and Ventilation of Buildings, 1009/2017.
  • National Building Code of Finland, Strength and stability of structures, Design of foundations (Ministry of the Environment, 2018)
  • Rakennustieto Oy. Radonin torjunta. RT reference card RT 81-11099, LVI 37-10513, KH 27-00510. (Radon prevention, available in Finnish).

More info about National Building Code of Finland can be read on Ministry of the Environment website (

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