Selection and evaluation of commercial low-cost devices for indoor air quality monitoring in schools

The use of low-cost sensors for monitoring Indoor Air Quality (IAQ) in schools has shown promising results, with the commercialisation of these devices increasing worldwide. This study aims to identify an effective, commercially available low-cost device for IAQ monitoring in schools.

Four low-cost devices (AirVisual Pro, PocketLab Air, PurpleAir PA-II-SD and uRAD Monitor A3) were selected for both qualitative and performance evaluations. Field tests were conducted in six indoor microenvironments within a nursery and a primary school. The low-cost devices were co-located with research-grade instruments to obtain reference concentrations of PM₁, PM_2.5, PM₁₀, CO₂, VOC, formaldehyde and O₃.

The qualitative evaluation revealed limitations, including data loss, negative or erratic values, inconsistent timestamps, and connectivity issues. PM low-cost devices exhibited better performance during non-occupancy periods but faced challenges during periods of occupancy. All devices tended to underestimate measurements compared to reference data, although AirVisual Pro performed better for PM_2.5 during occupancy. Furthermore, CO₂ concentrations were slightly overestimated, showing improved accuracy during occupancy periods. While formaldehyde peaks were detected by the low-cost device, overall performance was weak for both formaldehyde and O₃.

The results indicated that AirVisual Pro demonstrated the best overall performance, and presents itself as a promising tool for IAQ monitoring in schools. However, performance evaluations should be tailored to specific microenvironments and occupancy periods. Despite some acceptable performance results, real-context use of the selected low-cost device should be preceded by a proper calibration. Additionally, long-term performance evaluation should be considered in future studies.