Radon
Radon is a naturally occurring radioactive gas that can seep from the ground and accumulate in homes, workplaces, and public buildings. The main reasons why it is essential to know how much radon is present in your home are:
– Radon causes more than 3,200 deaths every year in Italy alone;
– In many areas, over 10% of homes have radon levels higher than 100 Bq/m³, a level above which the World Health Organization considers radon a risk to the population;
– In areas classified as critical, the percentage of homes with radon levels exceeding 100 Bq/m³ rises to over 20%.
The home, where we spend most of our time, is the place where—also according to the latest updates from the ICRP (International Commission on Radiological Protection)—the risk is most significant.
Radon can be measured using PASSIVE or ACTIVE devices!
Measuring radon: differences between active and passive devices (CR-39)
Measuring radon in indoor environments is a fundamental step for protecting health and ensuring compliance with current regulations. Radon is a natural radioactive gas that is colorless and odorless, can accumulate inside buildings, and represents one of the leading causes of lung cancer after smoking. For this reason, measuring radon correctly and reliably is essential both in residential settings and in workplaces.
There are several technologies available to measure radon, mainly divided into active measuring devices and passive measuring devices, among which the most widely used are CR-39 nuclear track detectors. Understanding the differences between these instruments helps in choosing the most suitable solution for specific needs.
Active devices for detecting radon
Active devices used to measure radon are electronic instruments powered by an energy source (battery or mains electricity). These instruments continuously measure the concentration of radon in the air and provide results in real time or near real time.
Main features of active devices
Continuous measurement of radon concentration
Immediate data display, often via a screen
Possibility of time-based analysis (hourly, daily, or weekly trends)
High usefulness for diagnostic studies and rapid assessments
Thanks to their ability to record variations over time, active devices are particularly useful for:
analyzing the effect of ventilation,
verifying the effectiveness of remediation actions,
identifying peaks in radon concentration.
However, when it comes to measuring radon for regulatory purposes, active devices have some limitations: they are generally more expensive, and short-term measurements may not be representative of the average annual exposure. Below you will find a dedicated section where you can purchase them!
Passive devices for radon sampling: CR-39
Passive devices, such as CR-39 nuclear track detectors, are the most widely used solution for measuring radon over long periods. These instruments do not require an electrical power supply and operate using a plastic material that is sensitive to alpha particles emitted by radon and its decay products.
How CR-39 works
During the exposure period, alpha particles strike the CR-39 material, creating micro-tracks that are invisible to the naked eye. At the end of the measurement period, the detector is analyzed in a laboratory, where the tracks are made visible and counted to determine the average radon concentration.
Advantages of CR-39 passive devices
Ideal for long-term radon measurement (typically 3–12 months)
Provide an average value that is representative of real exposure
Easy to use, with no maintenance required
Lower cost compared to active devices
Widely recognized for official assessments and regulatory compliance
Because of these characteristics, CR-39 detectors are the reference tool for large-scale measurement campaigns and for verifying radon levels in buildings. Below you will find a dedicated section to purchase them, and don’t worry—you will be provided with all the guides, which you can also preview in advance: www.niton.it/guide/
Active or passive devices: which should you choose to measure radon?
The choice between active and passive devices depends on the objective of the measurement:
For rapid assessments, diagnostic studies, or dynamic monitoring, active devices are more suitable.
To measure radon reliably and representatively over the long term, passive CR-39 devices are the preferred solution.
In many cases, the two technologies are used in a complementary way: radon is first measured using passive detectors to obtain an average value, and then active instruments are used to analyze variations in detail and to plan any necessary mitigation measures.
