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Ionising radiation

Environmental Radioactivity - Medicine - Occupational Radiation Protection - Nuclear Hazards Defence

Ionisierende Strahlung

Where does radon occur?

Diagram of radon occurrence Occurrence of radon

In different concentrations, radon occurs everywhere in our environment.

From the underground of buildings radon also gets indoors, where it can accumulate. In particular when houses are only ventilated occasionally, this may lead to high radon concentrations that are dangerous to health.

The radon concentrations in the ground, in the air, and indoors vary locally and regionally.

Radon in pores of soil and rock

Radon in the soil

The propagation of radon depends on the permeability of the soil. Up to a depth of approx. one metre, the propagation of radon is also influenced by the weather conditions. Regionally, radon occurs in different concentrations in the soil.


Radon in building materials

Every building material from natural rock– depending on the geological origin – contains a natural share of uranium and radium. When uranium and radium decay, radon and its decay products are formed and released from the building material into the building. Measurements by the BfS prove that building materials contribute little to the indoor radon concentration.

Outdoor radon near the soil

Outdoor radon

When radon escapes from the soil to the surface, it is released into the ground-level atmosphere, where it mixes rapidly with the ambient air and generally occurs in low concentrations. Inhaling radon outdoors leads to a relatively low radiation exposure of 0.1 millisievert per year which is part of the natural radiation exposure and unavoidable.

Diagram of radon pathways through a building

Radon in buildings

Among others, the level of indoor radon concentration depends on how much radon is formed in the subsoil, how permeable the subsoil is for the radon transport and how the building has been constructed. The annual mean of the indoor radon concentration is 50 becquerel per cubic metre on average. The actual levels of indoor radon concentrations can only be determined by measurements.

Water glass filled from a tap

Radon in drinking water

Radon easily dissolves in water and can also enter buildings via water pipes: It is released from drinking water during cooking and showering or taken up during drinking, thus contributing to the radiation exposure of man. The Commission on Radiological Protection recommends that the radon concentration in drinking water does not exceed 100 becquerel per litre. The BfS carried out comprehensive measurements of radon in German drinking water.

© Bundesamt für Strahlenschutz