You cannot sense radon ‒ a measurement is the only way to determine radon levels in dwellings

10.2.2023 14:16

A measurement is the only way to determine the radon level in a dwelling because radon is an invisible and odourless radioactive gas which can occur in the indoor air in any Finnish building. Radon is produced in the soil, and the soil beneath a building is the most important radon source for indoor air. A long stay in rooms with high radon concentration can be associated with a higher risk of developing lung cancer. Radon does not cause allergic reactions or general symptoms, such as dizziness or fatigue.

Radon levels in dwellings rarely measured

Radon occurs all over Finland, but mostly in Southeast Finland and Pirkanmaa. There are areas with high radon levels also in Western Lapland and North Karelia. To review radon levels in dwellings, visit Radon maps of Finland (

Even though radon occurs in Finland, the Radiation and Nuclear Safety Authority (STUK) has estimated that a radon measurement has been conducted in only about 10% of detached houses. Radon measurements should be conducted more commonly in detached houses, terraced houses and the first floor of high-rise buildings to ensure that the radon levels in indoor air are safe.

Measurement season is September–May

Radon measurements use a so-called box method, where a detector is placed in the room for at least two months during the measurement season from 1 September to 30 May. The reference value for indoor air radon concentration in dwellings is 300 becquerels per cubic metre which should not be exceeded. Instructions for radon measurements in dwellings can be found (in Finnish) on the STUK website (

Usually, measurements are ordered by the owner of the dwelling or the housing company (the board or the building manager), but a tenant can also order one for their home. The municipal supervisory authority controls radon levels in dwellings based on suspected adverse health effects. Municipal supervisory authorities control other premises, such as schools and kindergartens, in connection with regular control visits.

If radon is found, mitigation measures are generally related to sealing of leaks, ventilation technology or sub-slab-suction and radon well solutions. More information about radon mitigation can be found at the STUK website (

Further information: Senior Officer Titta Manninen, tel. +358 295 209 398