RESUMO
Over the last 10 years, as a possible alternative to the conventional approach to air quality monitoring, real-time monitoring systems that use low-cost sensors and sensor platforms have been frequently applied. Generally, the long-term characteristics of low-cost PM sensors and monitoring have not been thoroughly documented except for a few widely used sensors and monitors. This article addresses the laboratory and field validation of three low-cost PM monitors of the same type that use the NOVA SDS011 PM sensor module over a 1-year period. In outdoor environments, we co-located low-cost PM monitors with GRIMM EDM180 monitors at the National Air Quality Monitoring stations. In indoor environments, we co-located them with a Turnkey Osiris PM monitor. Several performance aspects of the PM monitors were examined: operational data coverage, linearity of response, accuracy, precision, and inter-sensor variability. The obtained results show that inter-monitor R values were typically higher than 0.95 regardless of the environment. The tested monitors demonstrate high linearity in comparison with PM10 and PM2.5 concentrations measured in outdoor air with reference-equivalent instrumentation with R2 values ranging from 0.52 up to 0.83. In addition, very good agreement (R2 values ranging from 0.93 up to 0.97) with the gravimetric PM10 and PM2.5 method is obtained in the indoor environment (30 < RH < 70%). High RH (over 70%) negatively affected the PM monitors' response, especially in the case of PM10 concentrations (high overestimation).