There is a proliferation of inexpensive consumer-grade devices that could be used to monitor air pollutants, including PM2.5 particles and certain gasses. This study compared the performance of four consumer-grade devices – the Air Quality Egg 2 (AQE2), BlueAir Aware, Foobot, and Speck - which utilize optical sensors to measure PM2.5 concentration. The devices were collocated and operated in three residences for 7 days in each, and PM2.5 concentrations compared against established optical sensing devices, i.e., the personal DataRAM and DustTrak DRX, as well as PM2.5 mass concentration measured using a filter-based Personal Modular Impactor.
Overall, the Foobot and BlueAir had the strongest and significant correlations with the direct-reading reference instruments for both hourly and daily PM2.5 mass concentrations. Compared to the DustTrak DRX for 1-hour averages of all residences, Foobot had a Pearson’s correlation coefficient (R) of 0.80, while that for the BlueAir was 0.88, for the AQE2 it was -0.028, and for Speck 0.60. Overall, the strength of correlations depended on a particular residence, likely due to different aerosol composition. The correlation with filter-based measurements was moderate, and R values for the BlueAir, and Foobot were 0.44 and 0.56, respectively. The daily correlations for AQE2 and Speck were -0.61 and 0.69. The average 24-hr PM2.5 concentration data obtained by the consumer-grade monitors were statistically different (p>0.05) from the mass measured by gravimetric filters, according to a paired t-test. Overall, this study demonstrates the utility of consumer-grade air pollution monitors to report PM2.5 trends accurately; however, it suggests that for accurate mass concentration measurements, the monitors should be calibrated to a particular location and application. Further testing is needed to determine their applicability for long-term indoor field studies.