How radon enters buildings

Radon enters buildings from the soil, possibly leading to indoor air pollution. 

Chimney effect:

Roter Schleier vor Häusern

The infiltration of radon from the soil into buildings is mainly due to the so-called chimney effect: warm air rises indoors, leading to a barely perceptible drop in atmospheric pressure in the basement and lower storeys; this produces a suction effect, which may be increased by ventilators or chimneys. During the cold season, the suction effect in the basement is intensified when the heating is switched on.

Leaks in building envelope:

Whether radon can infiltrate depends largely on how airtight the building’s foundations are.

Examples of non-airtight elements of the building envelope:

  • Cracks and joints in walls and floors
  • Opening for windows and pipes
  • Dirt or gravel floors

Last modification 27.07.2018

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Federal Office of Public Health FOPH
Division of Radiological
Radiological Risk Section
Schwarzenburgstrasse 157
3003 Berne
Switzerland
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