The most common method of measuring radon concentration in the indoor air in a dwelling or workplace is an alpha track detector, which reveals the long-term mean concentration. In the workplace, the impact of cycled ventilation or local exhausts on indoor radon concentration can also be investigated. In connection with radon mitigation, the success of the chosen mitigation method can be investigated by means of a short radon measurement indicating the instantaneous radon concentration, based on which ventilation adjustments or additional measures will be made, if necessary.
When and how often should radon be measured?
The average radon concentration in a property can change due to many reasons. STUK is aware of cases where the sub-slab suction was broken without anyone noticing. As a result, human radon exposure was as high as before the radon mitigation. The pressure ratios of the property may also change, for example, after a window replacement: if significant amounts of replacement air came through the cracks in the old windows, the underpressure of the room may increase due to the new, tight windows, the ventilation may become weaker and the radon concentration may increase significantly. Therefore, the renewal of windows also counts as an essential change.
STUK recommends that indoor radon measurement be repeated in dwellings, workplaces and other occupied spaces
- every ten years if the previous radon concentration was higher than 100 Bq/m3
- every ten years if the reduction of the radon concentration below the reference value was achieved by radon mitigation
- every five years if a lower concentration than the reference value was achieved by radon mitigation and the radon concentration before the mitigation was higher than 1,000 Bq/m3
- as soon as possible after the building has undergone substantial structural or ventilation-related construction or alteration work (e.g. replacement of concrete slab, drains or ventilation).
Video: Is there radon in your home - measure and find out! (How to make a radon measurement)
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- Radiation Act 859/2018 (Finlex)
- Government Decree on Ionizing Radiation 1034/2018 (Finlex)
- Decree of the Ministry of Social Affairs and Health on ionizing radiation 1044/2018 (Finlex)
- Radiation and Nuclear Safety Authority Regulation on Practices that Cause Exposure to Natural Radiation STUK S/6/2022 (Stuklex)
- Radon Atlas of Finland (STUK-A245) (Julkari.fi)