What the number on your radon report means
Bq/m³ means radioactive decays per second in each cubic metre of indoor air. That is the unit used on UK domestic radon reports.
A standard UK domestic test uses two passive detectors, one in the living area and one in an occupied bedroom, left in place for about three months. The laboratory combines the two readings, weights them for typical occupancy and applies a seasonal correction, because indoor radon is usually highest in winter and lowest in summer. The headline figure is therefore an estimated annual average, not the reading on one day.
Source: UKradon measuring radon. Guidance checked 26 October 2026.
Reading your result against the UK levels
| Your annual average | What UKHSA guidance says | Next step on this site |
|---|---|---|
| Below 100 Bq/m³ | Below the Target Level. Reduction is generally not needed. | Keep the report with your property documents. |
| 100 to 199 Bq/m³ | Between Target and Action Levels. Consider reducing it, especially if anyone in the home smokes or has smoked. | Remediation guidance |
| 200 Bq/m³ or more | At or above the Action Level. UKHSA recommends reducing radon, then re-testing after the work. | Remediation guidance and the official UKradon levels advice ↗ |
Cite: UKradon Action Level and Target Level. These are public-health references, not a sharp boundary between risk and no risk.
When a result is less reliable
UKradon notes that a result can be less reliable when the occupier changes during the test, the home is empty for more than a few weeks, building works take place, detectors are not placed within a week of arrival, or the test is shorter than three months.
Short-term (7–30 day) and electronic-monitor readings are screening measurements with greater uncertainty. Use them as an indication; compare with the Action Level using a validated long-term test.
Sources: UKradon measuring radon; UKHSA validation scheme (2018).
Readings from a digital radon monitor
Consumer monitors show short-term values that swing with weather and ventilation. Treat them as an indication only. To compare with the Action Level, use a validated long-term laboratory test. See the detector guide for the difference between passive kits and electronic monitors.
Workplaces are different
Workplace radon is regulated under the Ionising Radiations Regulations 2017 (IRR17). The Health and Safety Executive (HSE) reference level for workplaces is 300 Bq/m³ as an annual average, with duties on the employer. Homes still use the UKHSA Action Level of 200 Bq/m³ and Target Level of 100 Bq/m³. This page covers homes only.
Source checked 26 October 2026: HSE radon at work.
Radon test results FAQ
Is my radon level safe?
Radon Map Check does not label a concentration as safe or unsafe. UKHSA guidance is that risk rises with concentration and with time spent exposed. Compare your annual average with the Action and Target Levels, then follow your laboratory report and official UKradon advice. Contact a qualified health professional for personal medical questions.
Why is my result different from the radon map band?
The map shows the probability that homes in an area will exceed the Action Level. A test measures radon in your building. Neighbouring homes can differ. Use the postcode check walkthrough to understand what a map band does and does not tell you.
Do I need to re-test?
After remediation work, arrange a follow-up measurement to assess the result. After major building work, or if detectors were misplaced during the first test, consider testing again. Agree a plan with your measurement provider or contractor.
Can I use a radon result when selling a house?
A measurement report is factual information that can be shared with a buyer. It does not certify the property or replace professional conveyancing advice. See UKradon's house-sales guidance and this site's homebuyer section. This is not legal advice.
Sources
- UKradon — Measuring radon
- UKradon — Action Level and Target Level
- HSE — Radon in the workplace
- Radon Map Check — About radon risk
- Radon Map Check — Detectors
- Radon Map Check — Remediation
Facts on this page were checked against the linked official pages on 26 October 2026. UKradon and UKHSA remain the authority on your result.