Radon in a home in Norway: limits, measuring and remedies (2026)

In Norway, radon should be reduced above the action level of 100 Bq/m³, and the level should in any case stay below the maximum of 200 Bq/m³, measured as an annual mean. Radon is an invisible, odourless gas that seeps up from the ground, and over time high levels are a health risk. The good news is that it is simple to measure and usually straightforward to lower. A winter measurement gives you the answer you need.

The limits: 100 and 200 Bq/m³

Radon is measured in becquerel per cubic metre of air (Bq/m³) and judged as an annual mean, the average over a longer period. Two limits are worth remembering.

Limit	Level (annual mean)	What it means
Action level	100 Bq/m³	Above this you should take steps to reduce the level
Maximum level	200 Bq/m³	The level should in any case stay below this

The limits apply to living rooms on the lowest occupied floors, where people spend time. A single high spot reading means little on its own; it is the annual mean that decides whether the home needs action.

How to measure: a winter measurement

Radon is measured with track-etch detectors, small measuring badges you place around the home and leave for at least two months. The measurement should be done in the winter half-year, typically between October and April, because that is when we heat and ventilate least and indoor radon is highest. That gives you an annual mean with a realistic picture.

Place the badges in living rooms on the lowest occupied floors, for example the living room and bedrooms on the ground or basement floor. A shorter measurement over a few days can give a pointer, but it is too uncertain to decide whether the level sits above 100 or 200 Bq/m³. For a judgment against the limits, it is the winter measurement that counts.

Common remedies if the level is high

If the annual mean is above the action level, there are several ways to lower it. Which measure fits depends on how high the level is and how the home is built.

• Sealing cracks and penetrations in floors and walls against the ground, so less radon gets in.
• Improving ventilation in the living rooms, so the air is changed more often.
• Fitting a radon sump, a fan system that draws air out from beneath the building before the radon reaches inside.

After a measure, you should measure again to confirm the level has actually come down. The cost varies with which measure is needed, and belongs in your budget the same way as other maintenance work.

New builds: a radon barrier is required

For new buildings with rooms for lasting occupancy, the building rules (TEK17) require radon protection. The building must have a radon barrier against the ground and an activatable measure to vent radon, and the annual mean must be below 200 Bq/m³. If you buy new, radon is handled through the regulations.

For an older home there is no equivalent requirement, so a measurement is what gives you the answer. If no measurement has been done, neither you nor the seller knows what the level is.

Radon and the condition report

A condition report describes the technical condition of the building and need not include a radon measurement. If a measurement has been done, the result may be attached to the sales prospectus, and then you should read it. Finding no measurement does not mean the level is high or low, only that it has not been measured. You can ask the seller for any earlier results, or plan your own winter measurement after takeover. Radon is something you can investigate, not something that has to stay unknown.

Heimer reads the sales prospectus and surfaces what affects the total price and the maintenance, so you know what to investigate before you bid. Paste the listing.