Radon in Finnish apartment buildings.

The 106 866 dwellings measured for radon in Finland so far by Radiation and Nuclear Safety Authority include 5560 apartments. The radon concentrations in ground-contact apartments are similar to those in low-rise residential buildings located in the same area. The values in apartments above the first floor do not significantly depend on the floor level, being typically one-third of those in ground-contact apartments. The radon values in new ground-contact apartments are lower than in those built in the 1990s, apparently because of lesser soil gas intake into new buildings. Radon in upper floors originates from building materials, and concentrations there have remained unaltered.