Understanding radon in your building

What is radon?

Radon is a naturally occurring radioactive gas released from soil and rock. Invisible and odourless, it cannot be detected by the senses. It can enter buildings and accumulate indoors.

Conditions depend on both the ground and the building. Location provides an initial indication, but a regional map cannot determine the concentration in your rooms. Measurement establishes the actual situation in the building.

How does it enter and move through a building?

Radon can enter from the ground through cracks, joints, pipe penetrations or earth and gravel floors. Small pressure differences between the ground and the interior can encourage this movement.

As warm air rises inside a building, it can create slightly lower pressure on the lower floors: this is the stack effect. Some extraction systems can also draw more air in from the ground.

Once inside, radon can move between rooms and up to higher floors. Room use and ventilation affect concentrations. This is why the survey examines several rooms simultaneously in the context of the building’s layout.

Why does it matter?

The risk is linked to radon concentration in the air and the duration of exposure. When inhaled, its decay products can irradiate lung tissue. According to the FOPH, radon is the leading cause of lung cancer after smoking.

In Switzerland, the reference level is 300 Bq/m³ for the annual average concentration in rooms where people regularly spend several hours a day. Becquerels per cubic metre express the radioactive activity of radon per volume of air.

The aim is to establish exposure and reduce it where warranted, taking occupied rooms and the way the building operates into account.

How can you assess your building?

You do not need to choose a device or measurement duration yourself. We start with your needs: assessing the situation, preparing a purchase or renovation, or following up an existing result.

• No previous measurements: we consider the location, building characteristics, occupancy and your timeframe before proposing an in-depth survey or measurements using passive detectors.
• To understand the building promptly: the survey involves approximately one week of simultaneous measurements in all rooms and other spaces in contact with the ground, with additional measurements on upper floors where needed. The analysis helps identify likely entry points and understand how radon moves through the building.
• Existing results: we review them first to identify useful investigations. Keep the complete report: duration, season, location and method provide context for the measured values.

When concentrations are low during the survey, passive detectors can confirm the result over a longer period. They are also offered when results call for further assessment. If a recognised measurement is required, we incorporate it into the process.

What happens if a problem is identified?

The technical survey provides the basis for a mitigation proposal suited to the building. Depending on its layout, the solution may address radon entry, ventilation or air pathways. Further tests may be needed to refine the technical choices.

Robert Gaisch carries out the mitigation work. Concentrations are monitored before and after the intervention to observe its effect and adjust the system if needed. A mitigation report describes the work and presents the results alongside their measurement conditions.

After the work, a passive detector campaign is arranged to confirm the results through a recognised measurement, according to the applicable schedule. Monitoring results is therefore part of the mitigation process.