Radon is a radioactive gas that originates from uranium. It occurs naturally in the ground and is the most common cause of radon problems in indoor air. Radon can also come from building materials. In Sweden, blue concrete building material is what causes problems. It was used as a building material between the years 1929-1975 and includes shale. Blue concrete may be high- or low-radiation depending on where the shale comes from.
The Swedish Radiation Safety Authority (SSM) estimates that about 500 people per year in Sweden die from cancer in the respiratory system, caused by radon. The risk increases with increased exposure to radon. The government has set a milestone that all homes should be below a limit of 200 Bq / m³ in year 2020. Since radon neither is visible nor smell, measurements are required to detect the gas, such measurements are performed by Eurofins.