Data set: Long-term deployment of low-cost sensor IoT CAPTOR nodes measuring O3 and NO2 in Barcelona (2022-2024)

This data set corresponds to a low-cost Internet of Things (IoT) sensor deployment with three sensors at three locations in the city of Barcelona, measuring ozone (O₃), nitrogen dioxide (NO₂), temperature (T) and relative humidity (RH) during the period July 2022 to February 2024. This long-term deployment can therefore be used to evaluate sensor data processing techniques, as well as for exposure studies. The IoT nodes included two Alphasense electrochemical sensors measuring O₃ and NO₂, as well as a DHT sensor measuring temperature and relative humidity, collecting hourly measures. This deployment was funded by MCIN/AEI by a DIDEROT project (PID2022-138155OB-I00 funded by MCIN/AEI/ 10.13039/501100011033) and AGAUR project (2021SGR-01059). The three sensors were collocated with reference stations at "Gala Placidia", "Palau Reial", and "Avenida Roma" (more details on the sites are available in the Readme.txt file). Ground-truth values can be found at Generalitat de Catalunya webpage: https://mediambient.gencat.cat/ca/05_ambits_dactuacio/atmosfera/qualitat_de_laire/vols-saber-que-respires/descarrega-de-dades/. We have also included a calibrated version of the data ('_calibrated_NN.csv'), for which a feed-forward neural network (FFNN) was employed to calibrate the O₃ and NO₂ sensors. Two extra columns representing the estimated O₃ and NO₂ values have been added. Regarding the sensor calibration methodology, we used the first month of deployment to calibrate the sensors, and we used the same model for the remainder of the deployment (>1.5 years). We cannot guarantee accurate estimations over such a long period. For more details on general sensor calibration, please refer to the following reference: "A data-driven framework for air quality sensor networks, Ferrer-Cid et al. 2024", "A comparative study of calibration methods for low-cost ozone sensors in IoT platforms, Ferrer-Cid et al. 2019", "Sampling trade-offs in duty-cycled systems for air quality low-cost sensors, Ferrer-Cid et al. 2022".