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Portable device for automatically monitoring presence of radon in buildings

The Institute of Microelectronics of Barcelona (IMB-CNM-CSIC) has collaborated in the design and development of a prototype for the detection of radon gas, a radioactive gas of natural origin that can be found in buildings. The prototype is the result of the CARE project, led by the company Alibava Systems, and developed by research centres and companies.

Silicon microdevices that are integrated into the sensor.  | IMB-CNM-CSIC

It is imperceptible, but it is the largest source of natural radiation exposure in humans (about half of the total, according to some sources). This is radon, a noble gas produced by the natural radioactive decay of uranium in soils and rocks.

Some geographic areas have higher levels of radon than others because of their geological characteristics. Outdoors, radon is not an issue. However, a problem arises in enclosed spaces that are not well ventilated, such as large buildings, basements or buildings with closed air-conditioning circuits. In such cases, radon accumulates and can reach levels that are harmful to health. The World Health Organisation (WHO) estimates that between 3 to 14% of lung cancer cases can be attributed to this gas.

Since 2018, the European directive (2013/59/Euratom) obliges governments to measure radon in workplaces which are located in risk areas and to reduce radon concentration in places where a minimum of 300 becquerels per cubic metre is recorded. 

The objective of the CARE project, in which CSIC participates, was to develop an automatic and affordable system for monitoring radon levels. The result is a device based on a silicon sensor manufactured in the IMB-CNM-CSIC Clean Room, which monitors radon levels automatically and remotely.

The prototype is still in the standardisation phase. The CARE initiative has been led by the company Alibava Systems and has involved the participation of two public research centres, the IMB-CNM-CSIC and the Galician Institute of High Energy Physics (IGFAE, by its initials in Galician) of the University of Santiago de Compostela, which has been responsible for carrying out the calibration and validation tests, both in its experimental facilities and in real environments. Galicia is, as a matter of fact, one of the areas inside Spain with the highest radon emissions, according to the Nuclear Safety Council. The companies ATI Sistemas SL, Radiansa Consulting SL, and Sensing & Control Systems SL are also participating in the project.

Measurements every half an hour or less

The IMB-CNM-CSIC has actively participated in the development of the semiconductor sensor incorporated in the prototype, whose sensitive area has been set at 800 mm2. For optimal sensitivity, it has been covered with 30 silicon sensors with sizes of 27 mm2, which have been manufactured in the Micro and Nanofabrication Clean Room of the IMB-CNM-CSIC. The latter is a Singular Scientific and Technological Infrastructure (ICTS, by its Spanish acronym) of the CSIC dedicated to the development and application of innovative technologies in the field of microelectronics.

"The biggest challenge has been silicon integration in the heart of the radon detector; the final characteristics of the system depend on its quality, stability and repeatability," says Salvador Hidalgo, IMB-CNM principal researcher of the project. "We have manufactured modular structures consisting of ten silicon detectors, of which three have been used for this prototype placed in a new way. This solution allows us to have a very flexible system, with a quick and easy adaptation depending on the application," he adds.

When the device is approved, it will be used in both public and private buildings, and in both the domestic and industrial sectors. "It will be marketed in different countries around the world where building regulations require an active radon monitoring," says Juan Herranz, director of Alibava Systems and coordinator of the project. "Besides the possibility of storing data in the cloud, the final device will have protocols to communicate with the most commonly used intelligent ventilation systems in buildings," he says.

"Current radon detectors on the market read passively, but this prototype makes it possible to automate the data collection process and the execution of corrective actions," compares Celeste Fleta, IMB-CNM-CSIC researcher on the project. "The concentration readings are processed in the sensor unit and the results are sent wirelessly to a control centre that executes the established safety procedures,”she adds about the prototype, which has shown an efficiency “10% higher than current systems” during the validation phase.

The device provides the ability to have a detection network distributed within the area to be controlled, accurately identifying possible risk areas to be able to take corrective measures in the spaces where it is necessary. It is a real-time monitoring, which increases the level of security.

The CARE project (Development of an automatic radon concentration monitoring system in buildings) has been funded by the Ministry of Science and Innovation in the 2016 Call for Collaboration Challenges (RTC-2016-5627-1). It is an industrial research project to facilitate collaboration and knowledge transfer between public institutions and companies.