Radon Testing

Radon is a radioactive gas that you cannot see or smell, and its concentration indoors depends on the geology under the building, its construction and how it is ventilated. The World Health Organization identifies radon as the second leading cause of lung cancer after smoking, and the first among never-smokers.

Because the risk is proportional to concentration and time of exposure, knowing your long-term average level is the essential first step. Testing is inexpensive and requires no specialist to get started.

Passive detectors (alpha-track and electret detectors) are small devices you leave in place for weeks or months and then send to a laboratory for analysis. They are the most common choice for the long-term measurements that regulations and health agencies recommend.

Continuous radon monitors are electronic devices that display the concentration over time. They are useful for seeing daily variations, checking a mitigation system, or getting an early indication — though a laboratory-analysed long-term test remains the standard for decisions.

Charcoal test kits measure over a few days only. They can be a quick screening tool, but short-term results should never be the sole basis for deciding whether to mitigate.

Place the detector in the lowest level of the building that is regularly occupied — a ground-floor living room or a basement office, for example — away from draughts, windows, exterior doors and heat sources.

Measure for at least 90 days, ideally including the heating season, when windows stay closed and radon accumulates most. Radon concentrations can change by a factor of two or more between day and night and between summer and winter, which is why long-term averages are the basis for every official reference level.

Results are reported in becquerels per cubic metre (Bq/m³) in Europe and picocuries per litre (pCi/L) in the United States (1 pCi/L ≈ 37 Bq/m³).

The EU Basic Safety Standards Directive (2013/59/Euratom) sets a maximum reference level of 300 Bq/m³ for homes and workplaces. The US EPA recommends action at 4 pCi/L (≈148 Bq/m³), and the WHO proposes a reference level of 100 Bq/m³ where feasible. If your long-term average is above the reference level that applies to you, the next step is mitigation — a set of well-established building techniques that reliably reduce indoor radon.