Q&A – When do you need to perform radon measurements in the workplace?

Every year, radon causes about 480 cases of lung cancer in Belgium. In specific cases, as an employer, you must carry out a measurement and – if necessary – take corrective measures. ​

What is radon and why is it dangerous?

Radon is a radioactive gas that occurs naturally in the soil. Radon occurs especially in rocky soil, hence the higher concentrations of radon in Wallonia. Building materials can also emit radon, albeit to a much lesser extent. Radon is odourless, colourless, and has no flavour, so it is not easily detectable.

In the open air, the concentration of the gas is harmless. But radon can enter the workplace through cracks, crevices, and openings in the ground. It accumulates in areas that are not or only poorly ventilated, where employees inhale it. The inhaled radon particles and decay products damage the lung tissue. Long-term exposure can even cause lung cancer.

When and how must you take measurements?

The concentration of radon in the workplace depends on the site’s soil, the building materials, and ventilation. Therefore, it differs from one building to the next, and from one region to another. You only need to perform a (one-time) measurement if:

  • the workplace is underground, or
  • the building is located in municipality that lies in a class 2 risk zone.

Check the risk zone map

A radon measurement is done over a period of three months. It’s best to do it during the winter. During the cold months, the workplace is usually less ventilated. Place one or more passive detectors in the workplace and at least one in the area belowground.

After the measurement, fill in a short questionnaire, and submit a declaration file to the FANC via www.radonatwork.be. You can also order radon tests via this website. The FANC checks whether companies that need to carry out a measurement actually do so.

When must you take corrective action?

The action level in Belgium is 400 Bq/m³. If this limit is exceeded, you, as an employer, must take measures at the workplace. A few examples:

  • You create an impermeable barrier against radon by sealing cracks and fissures in the floor.
  • Reduce radon concentrations by utilising ventilation and extraction pipes outside the building.

Afterwards, you must carry out a second radon measurement to test whether the measures taken are sufficient.

Need a helping hand?

Mensura can provide custom advice on radon and other workplace exposures. If you have a specific question, please contact us on +32 2 549 71 00 or info.edpb@mensura.be.

Mensura will help you develop a targeted approach

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