What is Radon, and should I worry?
Paul Vernon · Surveyor (retired)
Radon is a naturally occurring radioactive gas formed from the uranium present in all rocks and soils and can cause lung cancer. Radon gas is inert, colourless, and odourless and exists in the atmosphere in trace amounts. Outdoors everywhere and indoors, in many areas the radon levels are low and the risk to health is small. It is present throughout the UK, but the levels are quite low in the most populous areas. Because radon comes from the soil, the geology of an area helps predict the potential for elevated indoor radon levels.
The map below shows the distribution of Radon in the UK. The darker the colour on the map, the greater the chance of a high radon level in a building. Whilst some of the highest levels have been found in the south west, levels well above average have been found in some other parts of England and parts of Scotland, Wales and Northern Ireland. However, even in these areas most homes have low levels.Contains British Geological Survey materials © UKRI 
Radon and Buildings
Radon can enter a house through cracks or openings in the foundation. The differences in air pressure between the inside of a building and the soil around it also play an important role in radon entry. If the air pressure of a house is greater than the soil beneath it, radon will remain outside. However, if the air pressure of a house is lower than the surrounding soil (which is usually the case), the house will act as a vacuum, sucking radon gas inside. Other than buying a house that has evidence of either being built with Radon in mind or been subsequently adapted there is no simple way of comparing one house against another.
Identifying if there is a problem
As mentioned, every building has radon and in most areas the levels are low and of no real concern. Areas that have high levels have been subject to Radon Protection Measures in new buildings for the last 20-30 years (varies throughout the country).
Some buildings in "Radon Affected Areas" will have higher levels. PHE recommends that buildings in these areas should be tested for radon. The good news is that high levels can be reduced by simple building works.
If your home is in an area with high Radon levels, there are three simple steps you can follow:
- Check whether the property is in a Radon Affected Area. After looking at the map, you may choose to order a Radon Risk Report from PHE. At a cost of £3.90*
- If the property is in a Radon Affected Area, then you could order a radon measurement pack. Those from PHE cost £51.60* and involve two detectors placed in your home: one in the living area and one in an occupied bedroom. After three months you post the detectors back to them and they analyse the detectors and post the results to you.
- If the measure result is at or above the UK Action Level of 200 Bq m-3, then there are a variety of measures that can be taken. These are outlined on PHE's website.
* correct at the time of writing, Dec 2020
Of course, the difficulty with phases 2 and 3 is that this assumes that you already own the property or are prepared to wait for the outcome of surveys (if the current owner permits them, of course).
What could I do?
This all sounds very scary, and expensive, but if it transpires that there is an issue in your building it need not be. There are essentially 2 separate approaches to remedying the risk from Radon. Either stop the radon seeping into your home by sucking it out with a sump that diverts the radon from its route into the building (or ventilating the void if the house has one) or create a positive pressure in the building to prevent ingress of gases. The costs of these works can be up to about £2,500 for a sump or as little as £800 for a positive pressure system.
If it transpires that there may be an issue, but the evidence is not conclusive, you could get the solicitors to agree a “Radon Bond”. I have seen figures suggesting that this would not normally exceed about £2,500 and a timescale of say 6-12 months to allow for a period of testing and if necessary, remedial works.
Should I worry?
If we were to simply avoid areas where radon exists, then many areas, including Devon, Cornwall and much of Wales would be empty. Yet people have lived there for millennia and continue to do so, leading long and happy lives. I am not suggesting that Radon should be ignored - it does present a real threat to health. However, we should be pragmatic.
- Its distribution is geologically predictable.
- Even in these areas it is not universally present.
- It does not always present as a risk.
- It is measurable; and
- There are measures that can be taken if it is determined to be a problem.
Would I buy a house in a Radon Affected Area?
Yes, in fact I did. PHE's Radon Map shows 6 ranges of Radon in the UK. My home is in range 3 and one of the other guys at MyNestBox lives in zone 5.
I would look at the Radon map and determine whether I thought that my property was in a zone worthy of further consideration. If it was, or I was in any doubt, then I would spend the £3.90 for a report. If I then felt it warranted further investigation or advice, then I would seek out specialist advice.