The short answer
The best radon mitigation method depends on the building and the test result. An active sump can extract ground air below a solid floor; ventilation methods may suit other construction types. Always verify the outcome with a new test.
Illustrative system layout. A specialist must design an installation for the property.
Radon sump systems
An active sump uses a fan and pipework to draw radon-containing air from beneath the floor and discharge it outside. UKHSA describes an active sump with a fan as the most effective way to reduce indoor radon. Sumps work best under solid floors, and under suspended floors where the ground below is covered with concrete or a membrane.
Positive ventilation
A fan introduces air into the home, commonly from a roof space. This can change the balance of air pressure and dilute indoor radon. Suitability depends on the starting concentration, layout and ventilation strategy; it is not a universal replacement for extraction.
Under-floor ventilation
Homes with suspended floors have a void below the occupied space. Improving natural airflow through that void, or adding mechanical ventilation, can help reduce radon. A specialist should consider moisture, air paths and the effects of any changes.
Is sealing enough?
Sealing gaps can support an effective system, but UKHSA says simple measures such as sealing large openings or adding extra ventilation do not reduce radon on their own. Completely sealing a floor is difficult and can cause rot in wooden floors.
Installation is only part of the job
Agree the discharge location, noise expectations, power supply and maintenance requirements in writing. Retest after the installation to establish the new radon level. Keep instructions so the system can remain operational over time.
Sources & further reading
UKHSA: reducing radon levels and historical costs ↗UKHSA: Action Level and Target Level ↗Checked 13 September 2026. General property guidance; use the original source and seek professional advice for your circumstances.