Radon is a colourless and odourless gas that is formed within the ground by the radioactive decay of the small amounts of uranium that occur naturally in rocks and soils and also exists within the atmosphere. Outdoors radon is generally not a health concern, but when it gets trapped indoors it can be dangerous. Exposure to high levels of radon for prolonged periods can increase the risk of developing lung cancer. In fact, radon is the biggest cause of lung cancer in non-smokers and the second overall behind smoking. Due to local difference in geology, the risk of exposure to radon gas differs depending on where you live.

PHE publishes reports containing radon Affected Area maps for the whole of the United Kingdom that can be found at WWW.UKRADON.ORG. There is an INTERACTIVE MAP where you can enter your postcode to see the maximum radon potential in your area. Amounts of radon are measured in becquerels per cubic meter of air (Bq m3). The average level in UK homes is 20 Bq m3 and where levels are below 100 Bq m3 your individual risk remains relatively low and not a cause for concern. The Radon Action Level is 200Bq m3 and BRE REPORT BR211 provides guidance on ‘basic radon protective measures’ appropriate in areas where 3% to 10% of homes are predicted to have radon at or above the Action Level and ‘full radon protective measures’ in areas where more than 10% of homes are predicted to have radon at or above the Radon Action Level.

PART C of the Building Regulations in England requires that where new buildings or extensions to existing buildings are constructed in high radon areas that protective measures are taken against radon entering the building. The floors and walls of dwellings often contain small cracks and gaps, and radon from the ground can be drawn into the building through these cracks and gaps because the atmospheric pressure inside the building is usually slightly lower than the pressure in the underlying soil. Approved Document PART C paragraph 4.2 requires that floors next to the ground should resist the passage of ground gases such as radon or methane and that remedial measure can include a gas resistance barrier which, with proper detailing, can also function as a damp proof membrane. Paragraph 4.19 requires that suspended floors have a ventilated air space of at least 150mm below them with ventilation openings on opposing sides to prevents build ups on ground gases below the building.

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