Precision was excellent for the Foobot (coefficient of variation range: 5% to 8%) and AirBeam (2% to 9%), but poorer for the Speck (8% to 25%). All three photometers had a bias (< −82%) for welding fume. AirBeam bias was (−36%) for salt and (−83%) for welding fume. Speck bias was at 18% salt for ARD and −86% for welding fume. Foobot bias was (< −46%) for salt and welding fume aerosols. The Foobot bias was (−12%) for ARD and measurements were similar to the medium-cost instrument. Compared to reference instruments, mass concentrations measured with the Foobot (r-value = 0.99) and medium-cost photometer (r-value = 0.99) show strong correlation, whereas those from the Speck (r-value range 0.88 – 0.99) and AirBeam (0.7 – 0.96) were less correlated. Three of each type of CAM were included to estimate precision.

In a laboratory study, PM 2.5 measured with the CAMs and a medium-cost aerosol photometer (personal DataRAM 1500, Thermo Scientific) were compared to that from reference instruments for three aerosols (salt, welding fume, and Arizona road dust, ARD) at concentrations up to 8500 μg/m 3. We evaluated the accuracy, bias, and precision of three CAMs (Foobot from Airoxlab, Speck from Carnegie Mellon University, and AirBeam from HabitatMap) for measuring mass concentrations in occupational settings. Recently, inexpensive (<$300) consumer aerosol monitors (CAMs) targeted for use in homes have become available.

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