A case study evaluating the performance of a cost-effective optical particle counter coupled with a humidity compensation approach for ambient air monitoring of particulate matter

The spatial monitoring of submicron particles has become an essential issue due to their negative effects on human health. However, the use of high-cost and high-grade measurement instruments is a challenging investment cost. Thus, a cost-effective optical particle counter (OPC), which is improved measurement quality, has become a good candidate. In this study, two cost-effective OPCs, coupled with a heated inlet tube to reduce the effect of humidity on its measurements, were applied in the field to measure ambient PM₁₀, PM_2.5, and PM₁ over 1 month. Their 1-h-average and 24-h-average data were compared with those obtained from a reference-grade OPC and a beta attenuation monitor (BAM). In particular, the correlations between the measurement data obtained from them, the differences in the mean values of these data, and the relative errors were evaluated. The PM_2.5 data obtained from cost-effective OPCs were comparable to those from BAM at even under high humidity conditions, except for rainy days. The data obtained from the cost-effective OPCs also showed good correlations and low relative errors (i.e., < 7%) compared to the reference-grade OPC, with no significant difference in mean values in terms of the PM_2.5 and PM₁ data. Although the measurement of PM₁₀ by the cost-effective OPCs showed lower quality than PM_2.5 and PM₁, the relative errors were still acceptable (i.e., < 18%) compared with those in other studies. Therefore, the cost-effective OPC coupled with a heated inlet tube has the potential to serve as a real-time monitoring instrument for ambient PM_2.5 and PM₁.