What is Radon?

DateOct 8, 2015
AuthorAnnalise Searle


What is Radon? What are the potential sources? What are the potential risks?

Radon is a naturally occurring radioactive gas, produced by the radioactive decay of Uranium (238U) (1).

what is radon

Uranium is found in small quantities in all soils and rocks throughout the UK, with areas of elevated radon risk noted to include the granitic bedrocks in South West England and the Carboniferous Shale in the North West of England (10). Radon222 (Radium) has a half-life* of approximately 3.8 days (2). The length of time it takes Radon to decay, enables the radioactive gas to diffuse great distances along geological strata. The gas then accumulates in buildings where homeowners are at a high potential risk.

Significant health implications can occur when radon is produced and diffused into residential and commercial properties (3). However, it should be noted that little harm occurs as long as the radon source remains outside the body. Problems arise when particles enter the body via inhalation or ingestion. Radon can stick to dust and moisture which is inhaled and can remain in the lungs (3) and this can increase the potential for lung cancer (4). Statistics held by Public Health England (PHE) show that Radon causes up to 1,100 deaths from lung cancer each year (9).

Where is it most likely to be found in the UK?

The average (mean) UK radon level is 20 becquerels per cubic metre of air (Bqm-3 (5), with the UK Radon Action Level (RAL) at 200 Bqm-3. The RAL is a level above which it is recommended that radon levels should be reduced, ideally to below the Target Level of 100 Bqm-3. Academics from a number of universities and the British Geological Survey (BGS) have studied locations throughout the UK with high radon emission levels. South West England, Scotland, Derbyshire and Northamptonshire were areas found to be above the UK RAL (6). The BGS/PHE national radon map also identifies medium risk areas in South East England.

radon map
Figure 1: Percentage of homes at or above the action level within the UK. Edited from Miles et al, 2007

What is the value of a getting a radon search in a property transaction?

It is important to get a radon search when buying a property. If a building has been identified to lie within an area that is at/or above the RAL (which can be established by ordering one the products provided by Groundsure) it allows you to make a more informed decision on whether you wish to proceed with the property transaction. Or highlight the need for a property specific assessment.

A property specific assessment (a home measurement pack) can be ordered through PHE (www.ukradon.org). The process involves placing 2 detectors within the living room and bedroom for a period of 3 months. The detectors are then returned to Public Health England in a prepaid envelope. The results of the analysis and any advice for further action will be posted to the home owner four weeks after the detectors have been returned. Every house is different and the migration of radon gas will vary depending on the property type and age. This highlights the importance of obtaining property-specific tests. A workplace measurement pack can also be obtained from PHE.

If your property has been identified to lie within a radon affected area, it is recommended that remedial measures are installed into an existing property. There are three primary ways to reduce radon in existing properties.

These include:

  • Installation of sumps (effective for all elevated radon levels),
  • improved underfloor ventilation (“natural” which is suitable for up to 500Bqm-3 or “mechanical” which is suitable for all elevated levels), and
  • positive house ventilation (which is effective for radon levels up to 500Bqm-3)

Further details can be seen on the BRE website

If you plan to extend an existing building, or undertake a new development it is required that “reasonable precautions shall be taken to avoid danger to health and safety caused by contaminants on or in the ground covered,” (8). Guidance on installing protective measures for new buildings has been published in guidance documents BR211 (for England and Wales) and BR376 (Scotland) and BR413 (Northern Ireland). These should be reviewed prior to the commencement of any development.

If you are purchasing a property within a Radon Affected Area it is advisable that the property transaction includes a Radon Bond. This is an agreement between the buyer and vendor whereby a sum of money held back from the sale to help with any potential remedial costs.

Important facts about Radon Bonds:

  • Typical remediation costs are around £1000
  • A typical retention sum is between £500 and £2000
  • The money is initially held by one of the solicitors for a period of six months, to allow time for moving in, the three month test, analysis and receipt of the report
  • If the result is below the Action Level, the money returns to the seller
  • If the result is higher, the money pays for remedial works and a timescale is agreed to allow for the works and a further test
  • Any surplus money goes to the seller.

Please note that a Radon Bond may not be suitable when the buyers are planning to carry out major building work as soon as they move in or if the buyers are not planning to move in straight away.

An article published by the BBC indicates that PHE have identified around 18,000 households in Gloucestershire which require radon gas testing. PHE have commented that they estimate a higher than usual chance that homes in those areas will have high radon levels (7). These homes will be given a free home measurement pack.

For more information please click here

Groundsure Reports

The Groundsure suite of commercial and residential searches contains up-to-date data supplied by the BGS, who in 2007 launched a joint data set with the aid of the Health Protection Agency (now known as Public Health England). The dataset uses long-term radon measurements from over 460,000 homes across England and Wales. The average indoor radon concentration was amalgamated with digital geological mapping. For further information and advice on radon, please contact Groundsure on +44 (0)1273 257 755 .


*The time taken for the radioactivity of a specified isotope to fall to half its original value.


  1. Public Health England. Radon. https://www.gov.uk/government/collections/radon. Accessed 12/07/2015.
  2. Nottingham City Council. What is Radon? http://www.nottinghamcity.gov.uk/article/23033/Radon. Accessed 12/07/2015.
  3. Ball.T.K., Cameron.D.G., Colman. T.B., & Roberts. P.D. (1991). Behaviour of radon in the geological environment: a review. Quarterly Journal of the Engineering Geology, 24: 169-182.
  4. Public Health England-UKradon. The risk to your health from Radon. http://www.ukradon.org/information/risks. Date accessed 13/07/2015.
  5. Gillmore. G.K., Phillips. P.S., and Denman. A.R. (2005). The effects of geology and the impact of seasonal correction factors on indoor radon levels: a case study approach. Journal of Environmental Radioactivity, 84: 469-479
  6. Miles. J.C.H., and Appleton.J.D.(2005). Mapping variation in radon potential both between and within geological units. Journal of Radiological Protection, 25: 257-276.
  7. BBC News Gloucestershire.(2014). Radon gas tests to be offered to Gloucestershire households. http://www.bbc.co.uk/news/uk-england-gloucestershire-30099973. Date accessed 12/07/2015.
  8. BRE- Protecting New Builds from Radon. http://www.bre.co.uk/page.jsp?id=3139. Accessed 4/06/2015.
  9. Ukradon. The risks to your health from radon. http://www.ukradon.org/information/risks. Accessed12/07/2015.
  10. The British Geological Survey. May 2012. Naturally occurring Radon. UK Geohazard Note.
  11. Miles.J.C. H., Appleton. J.D., Rees.D.M., Green. B.M.R., Adlam. K.A.M., and Myers.A.H. (2007). Indicative atlas of radon in England and Wales Chilton, HPA-RPD-033.