We conducted an exhaustive evaluation of low-cost platforms. The evaluation included laboratory testing against reference instruments in a controlled environment and field testing against reference instruments (co-location) under a range of different environmental conditions (e.g., weather, traffic). The results show clearly that a good performance in the laboratory is not indicative of a good performance in outdoor real-world conditions. The coefficient of determination in laboratory was above r2>0.9 for all the gases, while in field it showed a significant decrease, especially for NO2 and O3. This decrease in the performance is most probably due to interferences with temperature and relative humidity. Advances in algorithms to process the data might result in a higher performance of the sensors. Results also showed a high variability in the sensor responses from the same sensor type, making necessary to characterize sensor by sensor, even if by the same producer.
The high variability in individual sensor performance, as well as the variability in the performance depending on weather conditions or changes in emission patterns, etc. makes low-cost platforms difficult to use for applications when high data quality is necessary (i.e. air quality surveillance for regulation purposes). Low-cost sensors is a promising technology, with a rapid evolution in the market and the performance of the sensors is improving. However, the sensors are still in a research phase that requires an exhaustive testing and comprehension of the performance of each individual sensor platform before they can be deployed.
For more information, please contact Dr. Nuria Castell from NILU, Kjeller, Norway, email: firstname.lastname@example.org