Radon is a radioactive noble gas that rises from the ground and accumulates in indoor spaces. You cannot see, smell, or taste it. Measurement is the only option.
But radon fluctuates — hourly, daily, seasonally. A snapshot is worthless. That is why there are clear rules for a meaningful measurement.
How Long to Measure?
Minimum: 3 months. This is not an arbitrary value. Radon concentrations in buildings fluctuate by a factor of 5–10 within a few days depending on weather conditions, wind direction, air pressure, and ventilation behaviour. A 3-month measurement averages out these fluctuations.
Ideal period: heating season (October to March). In winter, windows are closed, heating creates negative pressure in the building (warm air rises and escapes at the top, ground air containing radon is drawn in from below), and radon concentration is at its highest. If you are below the reference level during the heating period, you will be below it throughout the year.
Short-term measurements (24–72 hours) with electronic devices provide only a snapshot. They can be useful as an initial screening, but do not replace a long-term measurement.
Where to Place Dosimeters?
Which room: The most frequently used living area on the ground floor or in the basement. Living room, home office, bedroom — wherever you spend the most time. Not in kitchen or bathroom (too much ventilation distorts the measurement).
Where in the room: - 1–1.5 metres height (breathing height) - At least 20 cm from the wall - Not directly by the window, not on the radiator, not in a draught - Not hidden behind furniture — the dosimeter should measure the room air, not the air in a corner
How Many Dosimeters?
Minimum: 1. In the most-used room.
Recommended: 2–3. One dosimeter in the basement (highest concentration), one on the ground floor (typical living area), possibly one in the bedroom (8 hours of exposure per night). This gives you a complete picture of the distribution within the building.
What Dosimeters Cost
€30–€50 per unit, including laboratory evaluation. Passive dosimeters (track-etch dosimeters) require no power, no maintenance — you place them and send them back to the laboratory after 3 months. Simpler than that it does not get.
What the Results Mean
The unit is becquerel per cubic metre (Bq/m³).
- Below 100 Bq/m³: Unremarkable. No action required.
- 100–300 Bq/m³: Simple measures recommended. Regular ventilation, sealing cracks and penetrations in the basement. This often suffices.
- Above 300 Bq/m³: Remediation measures recommended. The EU reference value is 300 Bq/m³. Possible measures: radon drainage, radon well, sealing the floor slab, controlled ventilation with heat recovery.
For comparison: the average in Austrian dwellings is approximately 100 Bq/m³, but there are massive regional differences. In parts of Upper Austria, Salzburg, Carinthia, and Styria we regularly measure values above 500 Bq/m³.
→ Radon in Austria — background
Next Step
You want to know how high the radon exposure is in your home? Get in touch — we will send you the dosimeters. 15-minute initial consultation, free of charge.