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A European project installs ozone sensors in the homes of citizens

Low cost sensors for measuring ozone have been installed in homes from rural areas. The obtained data can be seen on the Captor app and in real time. The CAPTOR project scientists and citizens working together in finding solutions for the problem of ozone pollution

Members of the Captor team installing the sensors.The Institut de Diagnosi Ambiental i Estudis de l’Aigua (IDAEA) of the CSIC is a partner in the project CAPTOR, which is led by Jorge García Vidal and José María Barceló, scientists of the Universitat Politècnica de Catalunya (UPC). CAPTOR is aimed at monitoring the tropospheric ozone pollution.


This 3-year project is funded by the Horizon 2020 program of the EU with 2 million Euros. Up to 8 partners are involved from Spain, Italy, Austria and France.

Internet of Things applied to sensors

In the frame of this project, scientists are implementing and monitoring a network of low-cost sensors. The sensors have been installed in volunteer houses, in order to get real information about air quality in those areas. The three chosen areas are very affected by tropospheric ozone pollution: Barcelones-Valles Oriental – Osona (Spain); the Pianura Padana (Po Valley, Italy); and Burgenland, Estíria and Lower Austria (Austria).

The sensors have been developed at the UPC, and its management and maintenance is carried out by the IDAEA-CSIC and the UPC. Anna Ripoll and Mar Viana, scientists at the IDAEA-CSIC, have also done the calibration of the sensors comparing the data obtained by the sensors to the data from reference laboratories and official stations.

These sensor devices are inspired by the ‘Internet of things’ technology (IoT). They are prepared with all the needed components to measure ozone and to send wirelessly the result via internet. Scientists now are testing two type of devices: the first one, based in Arduino technology (a free and open source platform for computing) and with ozone sensors of metal-oxide; the second one, based on Rapsberry Pi technology (a computing platform) and electrochemical ozone sensors.

As tropospheric ozone is formed mostly in summer, the scientists install and monitor the sensors in summer. This summer, until now, they have installed sensors in 12 homes in Catalunya (Spain) and 10 in Austria. After installing the ones in Italy, next days, they will have a total of 61 stations installed, the same that last year.

One of the developed devices.Making citizens aware of this pollutant

Tropospheric ozone is a secondary pollutant, formed by electrochemical reactions of nitrogen oxides (NOx) and volatile organic compounds (VOCs) when they are exposed to intense sunlight. This happens virtually always when the first gases, which are emitted mostly in big cities, have travelled far away of the emission points.

As a matter of fact, says Mar Viana, from the IDAEA-CSIC, if we have a look at the quality air maps, we can see how the points that indicate the ozone concentration increase their values as they get more and more distant of big cities.

That’s why tropospheric ozone is often an overlooked pollutant, because it has effects far away from the places where their precursors were emitted. The population that suffers the consequences are not the emissaries, and the ones who can contribute to reduce this pollution don’t suffer the effects.

With the CAPTOR project, citizens and scientists cooperate to deal with the ozone pollution problem in Europe. One of the goals is to boost cooperation among local communities, citizens, non governmental organizations and scientists to make society aware and to find out solutions.

Real time information of the sensors can be seen through the app CaptorAIR, which can be downloaded at the website or at Google Play. 

Another app has been also developed as a part of Captor project: airACT, which informs daily and every hour about air pollution. The values are provided by the official monitoring networks of every country.  

In Spain, the scientific team at the UPC have developed the sensor devices as well the algorithms for their calibration; the IDAEA scientists are in charge of analyzing the obtained data and calibrating the sensors; gives suport with the digital platform works; and the NGO Ecologistes en Acció is in charge of dissemination of information and public awareness tasks The project also has the support of the local government.

Air pollution is the environmental issue that worries most the European citizens. Up to 400,000 premature deaths every year are caused by air pollution. Also, it is the cause of significant damages in agriculture and the natural environment, according to the European Agency of Environment.


Project website

Data from the ozone sensors at volunteers houses last summer:

Vídeo about CAPTOR project:

Results obtained last year: