There has been a proliferation of inexpensive consumer-grade devices for monitoring air pollutants, including PM2.5 and certain gasses. This study compared the performance of four consumer-grade devices—the Air Quality Egg 2 (AQE2), BlueAir Aware, Foobot, and Speck—that utilize optical sensors to measure the PM2.5 concentration. The devices were collocated and operated for 7 days in each of three residences, and the PM2.5 mass concentrations were compared with those measured by established optical sensing devices, viz., the personal DataRAM and DustTrak DRX, as well as the filter-based Personal Modular Impactor (PMI).
Overall, the Foobot and BlueAir displayed the strongest correlations with the direct-reading reference instruments for both the hourly and daily PM2.5 mass concentrations. Comparing the 1-hour averages obtained with the DustTrak DRX for all of the residences with those obtained with the Foobot, BlueAir, AQE2, and Speck, the Pearson’s correlation coefficients (R’s) were 0.80, 0.88, –0.028, and 0.60, respectively. Overall, the strength of the correlation depended on the specific residence, likely due to the differences in aerosol composition. The correlations with the PMI measurements were moderate, with R values of 0.44 and 0.56 for the BlueAir and Foobot, respectively. The correlation coefficients for the daily values obtained with the AQE2 and Speck were –0.59 and 0.70 compared to the PMI. According to a paired t-test, the average 24-h PM2.5 concentration data obtained using the consumer-grade monitors were statistically different (p > 0.05) from the mass values measured by the gravimetric filters. Overall, this study demonstrates the ability of consumer-grade air pollution monitors to report PM2.5 trends accurately; however, for accurate mass concentration measurements, these monitors must be calibrated for a particular location and application. Further testing is needed to determine their suitability for long-term indoor field studies.