Radon in Finland

Finland has higher indoor air radon concentrations than most other countries. This can be explained by geology, construction technology and the climate. The average radon concentration in Finnish homes is approximately 96 becquerels per cubic metre (Bq/m3). This equals an annual radiation dose of approximately two millisieverts. Reduction of indoor radon concentration would be the most efficient means of decreasing the average radiation dose received by Finns. 

The average radon concentration (Bq/m3) in homes is 96 in Finland, 108 in Sweden, 106 in Norway, 77 in Denmark, 50 in Germany, 66 in France and 20 in England. 

The average radon concentrations and the percentage and estimated number of houses in which the radon concentration exceeds 200, 400 and 800 Bq/m3 (a sample survey conducted by STUK from 2006 to 2007).


average Bq/m3

>200 Bq/m3 % (dwellings)

>400 Bq/m3 % (dwellings)

>800 Bq/m3 % (dwellings)

Low-rise residential buildings


15.1 (204,000)

3.8 (51,000)

0.8 (11,000)

Blocks of flats


1.5 (16,000)

0.8 (8,000)


All dwellings


10.4 (220,000)

2.7 (59,000)

0.5 (11,000)


Radon (Rn-222) is a radioactive gas in the uranium series. Radon is produced from uranium (U-238) through a series of decay steps. The element preceding radon in the decay chain is radium (Ra-226). Radon further decays into a series of daughters; the final product is stable lead  (Pb-206).

The uranium concentration in our granitic bedrock and soil is higher than the global average.  In Finland, the regions of Lahti, Eastern Uusimaa and Kymenlaakso have the highest uranium concentrations, while North Karelia, Kainuu and Northern Lapland have the lowest. 

Moraines and sandy ridges that are very permeable to air are an inexhaustible source of radon-bearing air. Therefore, in houses built on ridges, radon concentrations are clearly higher compared with houses in the same area that are built on other types of soil. With regard to radon, raised steep-sloped moraines, such as Pispalanharju in Tampere and certain areas of Salpausselkä, are the most problematic.

Highest radon concentrations on ridges in Southern Finland

Homes and workplaces in which the radon level is above the 400 Bq/m3 maximum may be found anywhere in Finland, but they are found with the highest probability in Southern Finland and the Pirkanmaa region. Nearly 80 per cent of all dwellings that exceed the maximum level are located in the area formed by these regions. Most of these radon-rich dwellings are found on ridges or Salpausselkä formations.

In these areas, it is recommended to measure the radon concentration of all low-rise residential buildings, as well as first-floor flats and workplaces. The highest measured radon concentrations in a dwelling have exceeded 30,000 Bq/m3 (full year average). 

Between the sand, gravel and clay grains of soil there is air. The radon concentration of this air usually varies from 10,000 to 100,000 Bq/m3. In the worst areas, measured radon concentrations have exceeded one million becquerels per cubic metre.

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  • Katja Kojo / Inspector