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What is radon?

Radon is a radioactive gas which has no taste, colour or smell. It occurs naturally in all soils, although the amount found varies from place to place. Most of the radon from the ground rises to the surface and is quickly diluted into atmosphere. Concentrations in the open air is very low. However, radon that enters enclosed spaces such as buildings is not diluted so readily and it can reach high concentrations. Radon can enter a building through any cracks and gaps in the floor and walls.

Why worry about radon?

When radon decays, it forms minute particles of other radioactive substances. These are called radon decay products. If formed in the air these particles may be inhaled and some will be deposited in the lungs. The radiation emitted by them as they decay can give a high radiation dose to lung tissues and damage them. Exposure to high radon levels increases the risk of developing lung cancer.

Where is radon a problem?

High indoor levels are found principally in Cornwall, Devon, and parts of Derbyshire, Northamptonshire and Somerset, parts of the Grampians and Highland regions of Scotland, and the District Council areas of Down, and Newry and Mourne in Northern Ireland. It is also found to a lesser extent in other areas.

Radon Action Level

In 1990 the Government accepted the National Radiological Protection Board's advice of an Action Level of 200 becquerels per cubic metre of radon above which measures should be taken to reduce the concentration.

The Health Protection Agency has produced an 'Indicative Atlas of Radon in England and Wales'. The atlas provides the estimated percentage of homes in a 1km area above the radon Action level. Each 1km grid square is coloured according to the highest radon potential found within it. The Health Protection Agency recommends that all existing homes in a radon Affected Area should be tested for radon, concentrations above the Action Level of 200Bq/m3 should be reduced to as low as reasonably practicable, and new homes built in radon Affected Areas should be constructed with precautions against radon.

The estimated radon potential for an individual property can be obtained from the Health Protection Agency at, with the postcode and address. There is currently an online fee of £3.53 (inc VAT).

Radon in Tandridge

The areas declared as Radon affected areas with 1-3% of properties above the Action Level have been extended and previously undeclared areas have been identified with an estimated 3-5% of properties above the Action Level.

Previously the Health Protection Agency's Radiation Protection Division advised this Council that it had tested 38 houses in areas likely to be affected by radon and the arithmetic average concentration was 34Bq/m3, with none at or above the 200Bq/m3 Action Level. None of the testing revealed any premises with Radon above the Action Level in Tandridge and we are not aware of any further tests that support the declaration of new radon affected areas.

In order to comply with the Building Regulations, new houses and extensions in the 3-5% areas have to incorporate measures to reduce the likelihood of radon gas infiltration into the building.

Further information on radon

To view frequently asked questions on Radon, click on the following link Radon FAQs

For details of the Radon measurement service, click on the highlighted text.

For further information please telephone: 01235 831600. Alternatively you can email or write to:

Centre for Radiation, Chemical and Environmental Hazards
Radiation Protection Division
Oxfordshire OX11 0RQ