Radon Gas in UK Homes: Complete Guide to Testing, Risks and Mitigation
Radon is the second leading cause of lung cancer after smoking, causing around 1,100 deaths per year in the UK. This guide covers what radon is, which areas are affected, how to test your home, and what mitigation options are available.
Better Home Hub Editorial Team
TL;DR: Radon is a radioactive gas that causes approximately 1,100 lung cancer deaths per year in the UK. It is most common in Cornwall, Devon, Somerset, Northamptonshire, and Derbyshire. Test your home with a £30-£50 kit from ukradon.org. If levels exceed 200 Bq/m³, install a radon sump system (£800-£1,500) to reduce levels by up to 95%.
Last updated: April 2026
What Is Radon?
Radon is a naturally occurring radioactive gas produced by the decay of uranium found in all rocks and soils. It is colourless, odourless, and tasteless — you cannot detect it without specific testing equipment.
Radon seeps up from the ground and can accumulate inside buildings, particularly in enclosed spaces like ground-floor rooms, cellars, and basements. Outdoor levels are generally low (around 4 Bq/m³), but indoor levels can be hundreds or even thousands of times higher.
Why Is Radon Dangerous?
When radon gas decays, it produces tiny radioactive particles. When inhaled, these particles damage the cells lining the lungs, increasing the risk of lung cancer over time.
- Radon is the second leading cause of lung cancer after smoking (World Health Organisation)
- Approximately 1,100 lung cancer deaths per year in the UK are attributed to radon (UK Health Security Agency)
- The risk increases with higher radon concentrations and longer exposure
- Smokers exposed to radon have a 25 times greater risk of lung cancer than non-smokers in the same environment
Which Areas of the UK Have High Radon?
Radon levels vary dramatically across the UK depending on the underlying geology. The highest levels are found where granite and certain limestone rocks are present.
Highest Risk Areas
| Region | Risk Level | Percentage of Homes Above Action Level |
|---|---|---|
| Cornwall | Very High | Up to 30% in some areas |
| Devon | High | 10-20% |
| Somerset | High | 10-15% |
| Northamptonshire | High | 10-15% |
| Derbyshire (Peak District) | High | 10-20% |
| Parts of Wales (Powys, Ceredigion) | Moderate-High | 5-10% |
| Parts of Scotland (Highlands, Grampian) | Moderate | 3-5% |
Important: Even in low-risk areas, individual properties can have elevated radon levels. The only way to know is to test your specific property.
Check your postcode at ukradon.org to see the radon risk level for your area.
How to Test for Radon
Option 1: Passive Detector Test (Recommended)
The most accurate method is a 3-month passive test using two detectors placed in different rooms (typically the main living area and a bedroom). This gives a reliable long-term average.
- Cost: £30-£50 from UK Radon
- Duration: 3 months (ideally November-February when windows are closed more)
- Accuracy: High — accounts for daily and seasonal variations
Option 2: Digital Continuous Monitor
Electronic monitors provide ongoing real-time readings.
- Cost: £50-£200 for the device
- Accuracy: Good for trends, but less reliable than 3-month passive tests for risk assessment
- Useful for monitoring after mitigation work
Option 3: Professional Survey
For property sales or complex situations, a professional radon survey costs £150-£300 and provides a formal report suitable for conveyancing.
Understanding Your Results
| Level (Bq/m³) | Risk Category | Action Required |
|---|---|---|
| Below 100 | Low | No action needed (UK Target Level for new buildings) |
| 100-200 | Moderate | Consider mitigation, especially if you can do so easily |
| 200-500 | High (Above Action Level) | Mitigation strongly recommended within a few years |
| 500-1,000 | Very High | Mitigation recommended within months |
| Above 1,000 | Extremely High | Urgent mitigation required |
Radon Mitigation Methods
1. Radon Sump System (Most Effective)
A radon sump is a small pit dug beneath the floor, connected to a pipe that vents radon gas to the outside. It can be passive (relying on natural air movement) or active (using a small fan).
- Cost: £800-£1,500 installed
- Effectiveness: Reduces radon by 90-95%
- Running cost: £30-£50/year electricity (active systems)
- Best for: Properties with concrete floors, suspended floors, or basements
2. Positive Pressure Ventilation (PPV)
A fan unit in the loft pushes fresh air into the house, creating positive pressure that prevents radon entering from below.
- Cost: £500-£1,000 installed
- Effectiveness: Reduces radon by 50-70%
- Best for: Moderate radon levels (100-300 Bq/m³)
3. Natural Underfloor Ventilation
Improving airflow beneath suspended timber floors to disperse radon before it enters the living space.
- Cost: £200-£500 (adding or clearing air bricks)
- Effectiveness: Variable — depends on the property
- Best for: Properties with suspended timber floors and moderate levels
4. Sealing and Barriers
Sealing cracks, gaps around pipes, and installing radon barriers can reduce entry points.
- Cost: £100-£500 (DIY) or £300-£800 (professional)
- Effectiveness: Limited when used alone — best combined with other methods
Radon and Property Sales
During property conveyancing in radon-affected areas, solicitors typically request a radon search. If your property is in a high-risk area or tests show elevated levels:
- Buyers may request a radon test as a condition of purchase
- A high reading does not prevent a sale, but buyers may negotiate on price or request mitigation
- Having a radon mitigation system already installed provides reassurance and avoids delays
- Post-mitigation test results demonstrating low levels are valuable documentation
Case Study: Devon Bungalow
Property: 3-bed bungalow in Dartmoor National Park
Initial reading: 850 Bq/m³ (over 4x the Action Level)
Solution: Active radon sump system with external fan
Cost: £1,200 installed
Result: Radon level reduced to 35 Bq/m³ — well below the Target Level
Running cost: £40/year in electricity
Next Steps
Concerned about radon in your home? Get free, no-obligation quotes for radon testing and mitigation from certified specialists through Better Home Hub.
