Low- and Medium-Cost Sensors for Tropospheric Ozone Monitoring-Results of an Evaluation Study in Wroclaw, Poland

The paper presents the results of a 1.5-year evaluation study of low- and medium-cost ozone sensors. The tests covered electrochemical sensors: SensoriC O3 3E 1 (City Technology) and semiconductor gas sensors: SM50 OZU (Aeroqual), SP3-61-00 (FIS) and MQ131 (Winsen). Three copies of each sensor were enclosed in a measurement box and placed near the reference analyser (MLU 400). In the case of SensoriC O3 3E 1 sensors, the R-2 values for the 1-h data were above 0.90 for the first 9 months of deployment, but a performance deterioration was observed in the subsequent months (R-2 approximate to 0.6), due to sensor ageing processes. High linear relationships were observed for the SM50 devices (R-2 > 0.94), but some periodic data offsets were reported, making regular checking and recalibration necessary. Power-law functions were used in the case of SP3-61-00 (R-2 = 0.6-0.7) and MQ131 (R-2 = 0.4-0.7). Improvements in the fittings were observed for models that included temperature and relative humidity data. In the case of SP3-61-00, the R-2 values increased to above 0.82, while for MQ131 they increased to above 0.86. The study also showed that the measurement uncertainty of tested sensors meets the EU Directive 2008/50/EC requirements for indicative measurements and, in some cases, even for fixed measurements.

Automated summary

The paper presents the results of a 1.5-year evaluation study of low- and medium-cost ozone sensors. It discusses the performance, linear relationships, and measurement uncertainty of different sensor models. The study finds that sensor ageing processes can lead to performance deterioration, and periodic recalibration is necessary for certain sensor models. Improvements in fitting are observed when temperature and relative humidity data are taken into account. The measurement uncertainty of the tested sensors meets the requirements for indicative measurements and, in some cases, even for fixed measurements according to EU Directive 2008/50/EC.