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Radon gas

Image of the UK radon atlas.

Radon is a natural radioactive gas, originating from uranium which occurs in many types of rock. All water and air contains some radon, though levels are normally much too low to be of concern. For many years it has been recommended that, if the concentration of radon in indoor air exceeds the Action Level of 200 becquerels per cubic metre, steps should be taken to reduce it.

It is now recognised that some private water supplies contain levels of radon which should also be controlled. However, it is important to recognise that radon in water almost certainly presents a smaller public health hazard than radon in air, both in term of the numbers of people exposed to high levels, and in terms of the risks to the most exposed individuals. People living all their lives at the Action Level run the risk of a few percent of developing lung cancer. On average, about one in thirty people exposed for a lifetime at the Action Level would be expected to develop lung cancer.

New research suggests that around 1000 people may die each year as a result of radon, with smokers at a greatly increased risk.

Measuring Radon in the Home
The best guide to the level of radon in a building is a measurement kit from The Health Protection Agency. This takes three months - and an additional month or so to process and report the results. It is a simple procedure with monitors issued and returned by normal post, so no visit is required. The individual result for each home is confidential and will not be given to anyone else without the prior consent of the householder. The price includes the supply of two radon detectors (with full instructions for their use), subsequent analysis and reporting of the result. All packaging and the return postage costs are also included.

Radon levels in homes vary during the day, from one day to the next, and from winter to summer, mainly because of temperature differences between indoors and outdoors. They are generally higher at night and during the winter. Long term monitoring must be undertaken as Radon levels vary so much that it is not possible to predict with any certainty the long-term values from short-term measurements. Geiger-counters are unable to detect radiation from radon and its decay products at the levels found in homes.

Although radon enters homes all the time, some is carried away by the natural ventilation. Even in a home with good draught proofing and double glazing, the air changes several times a day. Increasing the ventilation, especially on the ground floor, will in most cases cause a moderate reduction in the radon level. Extractor fans can sometimes aggravate radon problems, if a suitable air inlet is not provided, as they may draw soil gas into the house.

Radon Reduction Even in Affected Areas most homes have low levels of radon and high levels can generally be reduced at fairly moderate cost. Concern about radon should not therefore influence your choice of home. The cost will vary with the type of work carried out. For simple measures, such as making sure airbricks are clear, it could be as little as a few tens of pounds. The average cost of a radon sump, the most effective way to reduce high levels, is about £1,500.00. Of course, if you are able to do the work yourself, the cost will be much less.

A Radon sump is a small void under a solid floor connected by a pipe to the outside. A small electric fan in the pipe continually sucks the radon from under the house and expels it harmlessly to the atmosphere. Modern sumps are often constructed from outside the house so there is no disruption inside. The power of the fan is typically around 75 watts; about the same as a light bulb and runs all the time.

Link to an external website. The Public Health England Radon map