Approved document C, Site preparation and resistance to contaminants and moisture, describes radon as:
‘…a naturally occurring radioactive colourless and odourless gas which is formed in small quantities by radioactive decay wherever uranium and radium are found. It can move through the subsoil and so into buildings. Some parts of the country, notably the West Country, have higher levels than elsewhere. Exposure to high levels for long periods increases the risk of developing lung cancer. To reduce this risk all new buildings, extensions and conversions, whether residential or non-domestic, built in areas where there may be elevated radon emissions, may need to incorporate precautions against radon.’
Radon is a naturally occurring radioactive gas released as part of the uranium 238 decay scale. All rocks and soils contain uranium – some more than others – e.g. granite, sandstone, limestone. It travels to the surface through gaps and cracks in the rock
Areas like Cornwall, where the rock is very fissured, means that radon can escape freely, so levels in buildings can be very high. Areas like Aberdeen, where the rock is very solid, the radon cannot escape and so radon levels tend to be very low.
Radon particles are so fine that our bodies don’t detect them – so unlike dust particles that make us cough – radon is breathed deep into the linings of our lungs. Radon gives a dose of alpha radiation, which has lots of energy, but cannot penetrate through skin, meaning that they release all of their energy in a very small area, damaging cells that can lead to cancerous growths. Radon is linked with approximately 1,100 lung cancer deaths each year in the UK and is the second cause of lung cancer next to smoking.
Radon can be drawn into buildings through cracks and gaps in the ground floor. Radon drawn up into a building gets trapped and can build to high levels, risking health with prolonged exposure. Public Health England advises government on a UK radon action level of 200 Bq per m3 (Becquerel per cubic metre).
There are tests you can do to find out your building’s radon level. Radon testing should be carried out over a long period (3 months) to allow seasonal adjustments to be made (radon levels are usually higher in winter than summer). Radon detectors are passive (small detectors placed and left – they do not need to be plugged in).
If your building has a high radon level, there are ways to combat this, including:
- Drawing radon away from beneath the building (a radon sump)
- Diluting radon levels in the building (positive ventilation)
- Diluting radon levels in floor voids beneath the property (either naturally or mechanically)
- Guidance about whether an area is susceptible to radon is available in BRE Report BR 211Radon: Guidance on protective measures for new buildings (including supplementary advice for extensions, conversions and refurbishment), 2007. The report also provides information about basic protective measures appropriate in areas where 3% to 10% of homes 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 of 200Bq/m^3.
- The Ionising Radiations Regulations 1999 (SI 1999/3232).
- BRE Report FB 41 Radon in the workplace: A guide for building owners and managers (Second edition), 2011.
- The Health and Safety Executive guidance on protection from radon in the workplace (www.hse.gov.uk/radiation/ionising/radon.htm).
See also Methane and other gasses from the ground, for information about gasses other than radon.
 Related articles on Designing Buildings Wiki
- Approved Document C.
- Brownfield land.
- Building on fill.
- Contaminated land.
- Cover systems for land regeneration - thickness of cover systems for contaminated land (BR465).
- Deleterious materials.
- Designing to reduce the chemical, biological and radiological vulnerability of new buildings (IP 7/15).
- Ground conditions.
- Landfill tax.
- Managing risks in existing buildings: An overview of UK risk-based legislation for commercial and industrial premises (FB 86).
- Methane and other gasses from the ground.
- Radon: Guidance on protective measures for new buildings BR 211.
- Site appraisal.
- Site investigation.
- Soil survey.
- Solid and liquid contaminants risk assessments.
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