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Cyngor Sir Ynys Môn - Isle of Anglesey County Council

Radon gas

Radon is a naturally occurring gas, which results from the radioactive decay of uranium.

It is found in small quantities in all rocks and soil. The gas disperses quickly in the open air, but can accumulate in buildings, especially in areas where the underlying ground contains higher than average traces of uranium and is permeable.

New homes are protected through the building regulation requirements in high radon areas. Measures to reduce the levels in existing homes may be installed at modest cost.

Prolonged exposure to high radon values is a health risk

  • Radon is a natural radioactive gas that enters buildings from the ground. You cannot see, hear, feel or taste it.
  • Radon is a natural radioactive gas that enters buildings from the ground. You cannot see, hear, feel or taste it.
  • Indoor radon is the largest source of radiation exposure to the public.
  • High radon values increases the risk of lung cancer in buildings where we live and work.
  • Radon in UK homes causes over 1000 cases of lung cancer each year, it’s the second most important cause of lung cancer after smoking.
  • Radon varies between buildings, between two houses next to each other and even between two homes in the same terrace.
  • High values are more common in some areas of Anglesey. The darker the colour on the map, the greater the risk of high levels.
  • The Health Protection Agency (HPA) conducts radon measurements. A detector pack for your home can be ordered from their website. Full instructions come with the pack.
  • Measurements are simple. Two detectors with instructions are posted to you, placed for three months and returned for analysis. All post and packing is included in the cost.
  • The result, with an explanation and advice, is provided by letter.
  • Other laboratories are validated to do radon measurements, a full list can be found on the HPA website.
  • The average value of radon in UK homes is 20 becquerels per cubic meter (Bq m-3).
  • The action level (AL) for radon in homes is 200 Bq m-3.
  • When high radon values are found, simple remedial measures are recommended which are generally simple and effective.
  • If you run a business, radon must not pose a risk to your staff. The HPA leaflet “Radon at Work” provides further information on this.


Contact Isle of Anglesey County Council's Environmental Services Section on 01248 752 820 or email

Conatct the HPA on 01235 822 622 or 0800 614 529 (freephone) or email

If you need a more accessible version, please email so that we can help you.