What is radon?
In one line: radon is a naturally occurring radioactive gas that seeps up from the ground into buildings, and it's a leading cause of lung cancer after smoking. A normal HEPA/carbon air purifier does not reliably remove it — the answer is testing and ventilation-based mitigation, not filtration.
What it is
Radon is a colourless, odourless radioactive gas produced by the natural breakdown of uranium in soil and rock. It rises from the ground and can accumulate indoors — especially in basements and ground floors — where it builds up if the space isn't well ventilated. Levels vary hugely by geology; some areas are "radon-affected" and others are negligible. Because you can't see or smell it, the only way to know your level is to test.
Why an air purifier doesn't fix it
Radon is a single gas atom, so a HEPA or MERV-13 particle filter passes it straight through — the same reason particle filters don't remove VOCs or smells. Activated carbon can adsorb some radon briefly, but it saturates and re-releases it, so a home carbon purifier isn't a dependable radon control either. Anyone selling an air purifier as a "radon remover" is overpromising.
What actually reduces radon
- Test first — a simple long-term radon test kit tells you your level. Check whether your area is radon-affected.
- Increase ventilation — more fresh air dilutes indoor radon, particularly in basements.
- Radon sump / sub-floor depressurisation — for high readings, a fitted mitigation system vents radon from beneath the floor to outside. This is the proven fix.
- Seal entry routes — gaps in floors and around services, as a supporting measure.
If a test shows a high level, use dedicated mitigation rather than relying on any air purifier.
Next step
A purifier still helps with dust and mould spores in a basement — see the basement guide — but treat radon as a separate, ventilation-based problem.
FAQ
Do air purifiers remove radon? Not reliably. HEPA filters don't touch gases, and carbon saturates and re-releases radon. Testing and ventilation-based mitigation are the real solutions.
How do I know if I have radon? Test — it's invisible and odourless. Use a radon test kit, especially if you're in a radon-affected area or spend time in a basement.