Low-cost sensor node for air quality monitoring: verification of NO2 measurements against a commercial system

In the light of the current respiratory disease pandemic, air quality gains relevance in cities around the world. Continuously monitoring trends of pollutants with a higher spatial and time resolution is desired to support the information from high quality stations. Given the availability of low-cost sensors and data transmission via wireless networks, it is possible to envision such monitoring with high quality at large scales. Facilitating that smart cities actively influence the distribution of pollutants, for instance, by active traffic control. Thus, offering citizens a better environment to live in. Our sensor-box prototype aims at monitoring air quality and other environmental parameters with lower cost sensors and components. Several challenges exist to achieve sensible measurements from metal oxide semiconductor (MOS) or from electro-chemical (EC) sensors such as: reproducibility, stability, uncertainty, drift, cross sensitivities. Here, the focus is on comparing nitrogen dioxide (NO2) measurements from these two families of low-cost sensors. Thus, we report on a side-by-side evaluation of the MOS sensor from a commercial system, and the EC sensor in our sensor-box. Recalibration of our EC sensors is demonstrated with a linear fit to the commercial system.