AS&T Highlight: Field Evaluation of Community Condensation Particle Counters, Optical Particle Counters, and a Low-cost Particle Sensor

By: Robert Nishida, University of Waterloo

Article by: Xiaoliang Wang, Patrick Myers, Matthew Claassen, Judith C. Chow, John G. Watson, Susanne Hering, Arantza Eiguren Fernandez, David Pariseau, Daniel Timmons, Ben McMullen, Craig Petersen, and Francisco Vega https://doi.org/10.1080/02786826.2025.2590103

While regulatory monitoring networks continue to rely on PM_2.5  and PM₁₀  mass concentrations, increasing attention to the distinct properties and effects of ultrafine particles (UFPs) has motivated the development of new measurement approaches. In addition, recent advances in low-cost particle sensing have expanded opportunities for community-scale monitoring, indoor and industrial applications, and distributed sensor networks. These trends have led to both “low-cost” optical particle sensors and “affordable” monitors, such as community condensation particle counters (cCPCs) and optical particle counters (OPCs), together enabling broader spatial and temporal coverage of a range of particle properties.

In this study, Wang and co-workers evaluate three such approaches: a community condensation particle counter (cCPC), an optical particle counter (OPC), and a low-cost optical sensor, each with distinct operating principles, operational requirements, and costs. Results were compared with two reference Beta Attenuation Monitors (BAMs) and gravimetric mass measurements for PM_2.5, PM₁₀, and related metrics.

The instruments were collocated at an urban monitoring site over four months. The cCPC, designed to measure particle number concentrations down to 5 nm, showed strong agreement with a reference CPC (R² > 0.99) and low inter-unit variability (3%), indicating good precision under field conditions, albeit within a temperature-controlled shelter. However, practical limitations remain, including a 10 s measurement cycle, the need for periodic refilling of working fluid, and underestimation (~15%) at higher particle concentrations relative to a reference CPC.

The OPC and low-cost optical sensor, both based on light scattering, were reasonably correlated with reference PM_2.5 mass concentrations, but did not capture particles smaller than 0.3 µm and therefore poorly represent ultrafine particles. The OPC showed reasonable correlation with the coarse particle fraction, whereas the low-cost optical sensor was unable to accurately measure the coarse particle fraction. Correlations with reference BAM measurements were evaluated only above a 5 µg/m³ concentration threshold, reflecting uncertainties in the BAM reference method, as well as in the lower-cost instruments, even at ambient concentrations considered relevant to human health in other contexts.

Overall, the study provides a useful field-based comparison of emerging “low-cost” and “affordable” particle monitors relative to established regulatory instruments, and highlights the current trade-offs between cost, measurement principle, and data interpretation. Each instrument exhibits its own uncertainties, operational constraints, and sensitivities; as such, cost alone does not necessarily determine measurement quality. Each method captures different aspects of the aerosol population, and results should be interpreted accordingly in both regulatory and community monitoring contexts.

Further reading:

Wang, X., Myers, P., Claassen, M., Chow, J. C., Watson, J. G., Hering, S., … Vega, F. (2026). Field evaluation of community condensation particle counters, optical particle counters, and a low-cost particle sensor. Aerosol Science and Technology, 60(3), 185–196. https://doi.org/10.1080/02786826.2025.2590103