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Radon Awareness: When to Best Measure Levels

The season for measuring radon is here. The measurements are made during the winter months, from October 1 to April 30, for the simple reason that buildings and homes are sealed up tighter during the winter months with closed doors and windows shut to keep in the heat, making measurement results more reliable; but, what is radon and why is it important to measure it periodically? Who is responsible?

We will guide you through the questions!

Radon article

What is radon?

Uranium is a radioactive metal found naturally in rocks and soil. Radioactive substances are constantly in a process of change; a so-called decay chain, where ionizing radiation is emitted. The substance radium, derived from uranium, is one of the decomposition products. As the radium in turn continues its process and decays, the radioactive noble gas, radon is formed. Radon gas continues to decompose into small radioactive metal particles, called radon daughters.

What are the health risks of radon?

The radon gas and radon daughters accompany our inhaled air and emit radiation that can damage the cells of our airways and lungs. Prolonged exposure to radon radiation can lead to lung cancer. Smokers are estimated to be 25 times more exposed than non-smokers, but even passive smokers have an increased risk. One likely reason is that radon gets stuck on the smoke particles that you breathe in.

However, the link between lung cancer and radon can be difficult to identify since the exposure does not give any direct symptoms and it can take up to 40 years from being exposed until lung cancer is detected.

“Radon is the second leading cause of lung cancer after smoking. Radon is responsible for about 21,000 lung cancer deaths every year.”

Source: United States Environmental Protection Agency

Where is radon?

Radon is naturally found in the soil. The concentrations in the outdoor air never become particularly high as the radon has a short half-life* (for four days) and the radon is diluted in large volumes of air. However, the radon levels in the soil are constantly high. This is because uranium from which radon is derived has an extremely long half-life – nearly 4.5 billion years. Therefore, constantly new radon is formed as long as the uranium in our soil is decaying, which it will continue to do for billions of years.

Radon can be sucked into any indoor environment (housing, workplaces, schools and public buildings). Unlike the outdoor radon content, the radon content in the indoor air is important to keep track of. The concentrations are higher than outdoors as the gas is concentrated on a much smaller air volume and we spend about 90% of our time indoors.

High levels of radon can occur in all types of house types and come from one or more of these three sources: the ground below and around the house, building materials and water from one's own well.

The ground

Most of the radon in indoor environments comes from the ground below and around the house. Indoor air pressure is lower than outdoors, ie. a vacuum, which allows air with radon to be sucked into the housing. How much radon is sucked in depends, among other things, on what kind of soil it is, how porous the soil is, how strong the suppression in the house is and the inputs there are for the air. Inputs can e.g. be cracks in floors and walls, pipes, drains, orifices and cracks, most so small that they cannot be seen with the eye.

Contact your local environmental and health protection office for information on the land where you live.

Building materials

All building materials containing stone emit radon, but it is mainly lightweight concrete with alum slate, also called blue concrete, which has such high levels that it becomes a problem. Blue concrete was used extensively during the 1950s and 1960s, before the problems were discovered and stopped production in 1975. However, the concrete continued to be used a few years after that.


Water from wells drilled in rocks and cold springs contains radon, especially if it is uranium-rich rocks. Municipal drinking water does not normally contain levels above the recommended value of 100 Bq/l, while rock-drilled wells can have 10 times as high levels, in some cases even more. The risks of drinking radon-containing water are small, however, the radon gas is spread from the water to the indoor air when used in the home.

How is radon measured?

Radon gas has no odor, color or taste, which means that you have to make a measurement. The content is measured in becquerel per cubic meter (Bq/m3).

Average outdoor levels are between 5–15 Bq/m3 while the average in indoor environments such as housing is 100 Bq/m3. The guideline for housing, workplaces above ground and schools is 200 Bq/m3. However, the goal should always be to have as low a radon content as possible to minimize the health risk.

The measurement period in Sweden is October 1st to April 30th.

The levels can vary greatly from day to day, but also during the day. The measurement should be done for at least two months to obtain an average content that is reliable. Before measuring the radon content, ventilation should be checked to make surer it works properly.

How to test for radon

Depending where you reside, it can be common to order measurement boxes yourself from a measurement laboratory or through your local environmental office. Even some home improvement stores offer test kits.

Keep in mind that the measurement result is not valid forever. The levels can be affected by the aging of the house, living habits, renovations and ventilation.

Who bears the responsibility?

It is the responsibility of the property owner to measure radon on his or her own initiative, as well as taking action if necessary. Unfortunately, the knowledge about radon is very low and many live in a house with radon levels that should be addressed.

Please note: QleanAir Scandinavia offers air filtration services but cannot help with radon remediation. In this Newsroom, however, we share all types of news and facts about air quality and its impact on our health; even in cases where we cannot provide the solution.

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