Radon is a radioactive noble gas, which forms naturally from uranium through a series of decay steps. Radon in the air can travel into the lungs, causing an increased risk of lung cancer. Smokers are more vulnerable to health risks caused by radon than non-smokers.

Our granitic bedrock, soil, and backfill under houses are the most significant sources of radon in Finnish houses, from which it can travel into a building via its foundations. There are approximately 2000 cases of lung cancer in Finland each year, of which around 200 are caused by radon.

High radon concentrations

According to the Decree on Ionizing Radiation (1044/2018) by the Ministry of Social Affairs and Health, the reference value for radon concentration in indoor air is 300 Bq/m³. New buildings must be designed and built so that radon concentrations do not exceed the reference value of 200 Bq/m³.

Radon concentrations can be decreased in old buildings as well. Sub-slab suction and radon wells are the most effective methods. Other methods include sealing leakage routes, such as cracks and seams in concrete, and improving ventilation in the house, the basement and in crawl spaces.

In Pirkanmaa, radon concentrations of over 300 Bq/m³ mostly occur in areas with moraines and sandy ridges that are very permeable to air.

Measuring radon concentrations

You can easily measure radon concentrations on your own by ordering a measuring kit from the Radiation and Nuclear Safety Authority (www.stuk.fi) and keeping it in your house for 2 months during winter. Radon concentrations in indoor air fluctuate seasonally. The greatest fluctuations happen in buildings that were built on permeable soil, such as on ridges.

Radon concentrations can be multiple times higher in winter compared to the summer. On ridges it can be up to ten times higher in winter. This is why measurements should be made during 1.9. - 31.5. Radon concentrations may vary drastically between different buildings in the same area.

Radon and construction

Dwellings and work places must be designed so that radon concentrations do not exceed the reference values. Radon seeps into indoor air from the soil beneath and around building, from drinking water from drilled wells, and from construction materials (in small amounts).

All construction sites should implement radon-safe building methods regardless of the kind of soil/bedrock surrounding it. These building methods are especially important in radon-rich areas. Radon mitigation afterwards can be expensive. The chosen foundation type of a building has a significant effect on the radon-technical procedures needed.

  • In buildings with a crawl space construction, it is considerably less common to find radon concentrations above the maximum value compared with houses that have a ground slab separately cast inside the foundation wall, given that the vents of the base floor are sized according to regulation and the floor slab is sealed tight.
  • For ground-supported base floors, the best solution is a base floor and foundation structure that is as joint-free and leakage-tight as possible, without much need for sealing. Any necessary seals should be done using something like rubber bitumen according to instructions. It is also possible to install radon piping under the floor slab.

Find more information on the Radiation and Nuclear Safety Authority website.