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Radon in the home
Radon is a natural, odourless, colourless radioactive gas that seeps up from the ground and can build up inside buildings. Over many years, high indoor levels raise the risk of lung cancer — it is the second-leading cause after smoking.
Where it comes from
Radon is released by uranium in soil and rock, so levels depend heavily on local geology. Areas with granite bedrock — including parts of the Nordic and Baltic countries — tend to be higher. It enters through cracks in floors and walls, gaps around pipes, and the lowest levels of a building, so ground-floor rooms and basements usually read highest.
You cannot sense it — you test for it
Because radon has no smell, colour or taste, the only way to know your level is a measurement. Long-term test kits (a small detector left in place for two to three months, ideally over winter) give a far more reliable picture than a short snapshot. Many countries run subsidised testing schemes.
If your level is high
Reducing radon is usually straightforward: sealing floor and wall cracks, improving under-floor ventilation, or fitting a sump system that draws the gas away before it enters. A specialist can advise once you have a measured level.
| Indoor radon | Guidance |
|---|---|
| Below 100 Bq/m³ | The WHO reference level — lower concern |
| 100–300 Bq/m³ | Worth reducing; the EU sets a maximum reference of 300 Bq/m³ |
| Above 300 Bq/m³ | Take action to reduce it |
This is general information. To learn your home's level, use a long-term test kit and follow your national radon authority's guidance — figures and action levels vary by country.
More on a healthier home
Bedroom temperature for sleep
A cool room helps you fall asleep and stay asleep. The usual sweet spot is around 16–19 °C.
Tap water and water hardness
In most of Europe tap water is safe and well tested. "Hard" or "soft" is about minerals, not safety.
Indoor humidity and mould
Aim for 30–50% relative humidity. Above 60% invites mould and dust mites; below 30% dries you out.
Ventilation and indoor air (CO₂)
Stuffy air is mostly a ventilation problem. Rising CO₂ tracks it and dents concentration.
Source: General building-health guidance (WHO indoor-air and radon references and national health and water authorities). · checked 2026-09-04
Frequently asked questions
How do I test for radon?
Use a long-term radon test kit — a small passive detector you leave in a lived-in ground-floor room for two to three months, preferably over the heating season, then send off for analysis. Short tests are far less reliable.
Is radon only a problem in basements?
Radon is usually highest in basements and ground-floor rooms because that is where it enters, but it can reach living spaces above. Homes in higher-risk geology are worth testing whatever the floor.
See what actually improves your sleep
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