Radon in your property — measurement, limits, responsibility

The reference level for radon in dwellings and in premises to which the public has access is 200 becquerel per cubic metre as an annual average, set out in the Swedish radiation protection ordinance (strålskyddsförordningen). As a property owner you are responsible under Chapter 9, Section 9 of the Environmental Code for ensuring levels in your dwellings do not exceed that value, for having the measurement carried out, and for paying for it. The supervisory authority is the municipal environmental committee (miljönämnden).

A reference level, not a limit value

The distinction is real and constantly misused. A limit value is a level that must not be exceeded. A reference level is a level that should not be exceeded and which triggers a duty to act when it is. In practice: if 200 Bq/m³ is exceeded in a dwelling you must investigate and remediate, and the environmental committee can order you to do so.

The value refers to an annual average, not an instantaneous reading. Radon levels vary sharply over the day and the year with temperature, wind and ventilation, which is why a short-term measurement can never serve as a basis for decisions.

How radon is measured — season and duration

Requirement	What applies
Measuring period	1 October – 30 April (the heating season)
Duration	At least 60 days, preferably longer
Method	Track-etch detectors for long-term measurement, accredited laboratory
Result	Annual average per measured space

The consequence of the measuring season is a planning one: miss the window and you wait six months. A radon measurement ordered in May yields nothing usable until after the turn of the year. It is the only one of the property owner's inspections with a window in the calendar rather than an interval — see the annual calendar.

How many flats must be measured for radon — all of them?

No. Under the Swedish Radiation Safety Authority's method description, measurement must be carried out in all flats with ground contact — those sitting directly on a slab or above a crawl space — and in at least one flat per floor higher up. Taken together, the measurements must cover at least 20 per cent of the flats in the building section, a section being the part served by its own ventilation system. If the building has several ventilation systems, the twenty-per-cent rule applies per section, not per house. The selection is not a statistical sample but targeted coverage: ground contact is the dominant radon source, which is why all such flats are measured.

How often should it be re-measured?

There is no statutory interval as there is for ventilation control. What governs instead are events and reasonableness:

After remediation — always a new measurement, otherwise nobody knows whether it worked.
After changes affecting ventilation or airtightness — window replacement, added insulation, rebuilt ventilation, pipe replacement.
On a change of owner, or where an earlier measurement is missing or old.
Where there is reason to believe conditions have changed.

A common practice in portfolios is to treat a measurement as current for ten years if nothing has happened to the building, but that is practice and not a legal requirement — the requirement is that the reference level is met, not that a measurement exists.

What to do when the level is too high

In the order that tends to pay off:

Investigate the source. Soil radon, building material (blue concrete) or radon in the water call for entirely different remedies. Without that investigation you are working blind.
Look at the ventilation first if it is undersized or not functioning. A ventilation measure solves some cases and is often the cheapest. Radon and ventilation control overlap here — see ventilation remarks.
Seal against the ground, or install a radon sump or radon well for soil radon.
Re-measure after the work, a full long-term measurement within the measuring season.

Remediation costs vary too much with building and cause for us to quote figures. The Swedish Radiation Safety Authority and Boverket are the sources for choice of method.

Premises and workplaces follow partly different rules

The 200 Bq/m³ reference level also applies to premises to which the public has access and to workplaces, but responsibility and method differ. In a workplace it is the employer who is responsible for keeping exposure below the reference level, and the Radiation Safety Authority has its own method description for workplace measurement where the assessment is based on the radon level during working hours rather than a pure annual average for the space.

That has a concrete consequence in a mixed portfolio: the same building may need two measurements — one under the dwelling methodology for the flats and one under the workplace methodology for the ground-floor premises, with different parties responsible. If tenants run their own businesses in their premises, it is worth settling who orders what before the measuring season starts, not during it. See radon in workplaces and premises.

What to require from the measurement provider

Radon measurement is a purchase where quality differences are invisible in the price. Four things to insist on:

An accredited laboratory for the analysis.
A measurement report stating placement per detector — without it the result cannot be tied back to the right flat.
Exposure time and measuring period reported per detector, so you can see the minimum 60 days within the season was met.
A statement of which spaces were included in the selection, so you can show the method description's coverage was achieved.

Point two is the one that usually fails. A results sheet with detector numbers but no flat numbers is effectively useless when the question a year later is which flat had 320 Bq/m³.

Radon in a larger portfolio

Two things make radon administratively awkward compared with the other inspections: the measurement covers many spaces per building, and the results come back as a list per detector several months after the work was ordered. That makes the link between order, detector, flat and result the place where things are lost.

In Emphyx, radon is handled as its own part of regulatory compliance, with a link to Radonova's ordering interface, so that measurements and results land on the right building rather than in a standalone report. We carry out no measurements and analyse no detectors — that is the measurement laboratory's work.

If you live in a rented flat or a housing co-operative, the property owner and the association respectively are responsible for measurement and remediation, not you as a resident.

Read on: radon above the reference level for what happens when a measurement comes back high, and radon in workplaces and premises if the portfolio contains let commercial space — responsibility and method are different there.