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What is Radon Gas ?

Radon gas emanates naturally from rocks and soils in the ground, mixes with air and rises to the surface where it is quickly diluted in the atmosphere. Concentrations in the open air are very low. However, radon that enters enclosed spaces, such as buildings, can reach relatively high concentrations in some circumstances.

  • Radon is a naturally occurring radioactive gas.
  • It comes from the minute amounts of uranium that occur naturally in most rocks and soils.
  • It has no odour, taste or colour (at standard temperature and pressure).
  • It can only be detected by using specialist equipment.
  • Radon is present throughout the country and in Thanet at levels that pose a low risk.

Where does it come from?

Radon gas is generated by the breakdown of radioactive radium, which in turn is the decay product of uranium, found in the earth's crust [1]. It is present in small quantities in most soils and rocks, although the amount varies from place to place. It is particularly prevalent in granite and limestone areas, but not exclusively so. Radon levels vary not only between different parts of the country, but even between neighbouring buildings. Most homes even in the higher radon affected areas will not have a radon problem. 

Action level for Radon

The Health Protection Agency (HPA) measures radon levels in Becquerel per cubic metres of air (Bq m-3) and have advised the government that a reading of 200 Bq m-3 in homes should be considered the ‘Action Level’. This is the level at which action should be taken to reduce the radon concentration.

Where is Radon gas found?

Public Health England and the British Geological Survey have jointly produced new information on radon Affected Areas in England and Wales. A new atlas was published on 12 Nov 2007 giving an overview of ‘Radon Affected Areas’ by km2 of the national grid. The atlas is indicative rather than definitive (ie. it refers to the maximum percentage band that exists within each km2 grid). This material replaces the existing Radon Atlas of England and Wales. These maps may be viewed at

Radon affected area

According to the new indicative atlas, most of the Thanet District now falls within a ‘Radon Affected Area’ (defined as an area where there is a 1% or more risk of homes being above the 200 Bq m-3 ‘Action Level’), and it highlights maximum percentage bands of 1-3% for most 1-km2 grids of the Thanet District.

However, this does not automatically mean that an individual property within these 1-km2 grids will have a radon problem. More accurate radon potential estimates for an individual home can be obtained through the following website:


[1] N.N. Greenwood and A. Earnshaw (1994) ‘Chemistry of the Elements’, Oxford: Pergamon Press, 1454-55.