Evaluation of consumer monitors to measure particulate matter

Abstract

Recently, inexpensive (<$300) consumer aerosol monitors (CAMs) targeted for use in homes have become available. 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. 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/m³. Three of each type of CAM were included to estimate precision. 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. The Foobot bias was (-12%) for ARD and measurements were similar to the medium-cost instrument. Foobot bias was (< -46%) for salt and welding fume aerosols. Speck bias was at 18% salt for ARD and -86% for welding fume. AirBeam bias was (-36%) for salt and (-83%) for welding fume. All three photometers had a bias (< -82%) for welding fume. 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%). These findings suggest that the Foobot, with a linear response to different aerosol types and good precision, can provide reasonable estimates of PM_2.5 in the workplace after site-specific calibration to account for particle size and composition.

Keywords: AirBeam; Foobot; Low-cost monitors; PM2.5; Speck; environmental monitoring; occupational monitoring.

Figure 1

Experimental set up used to determine the performance of the CAMs

Figure 2

Mass concentrations measured by consumer air quality monitors and the pDR-raw (uncorrected mass) relative to reference mass concentration for salt aerosol. The error bars represent one standard deviation.

Figure 3

Mass concentrations measured by consumer air quality monitors and the pDR-raw (uncorrected mass) relative to reference mass concentration for welding aerosol. The error bars represent one standard deviation.

Figure 4

Mass concentrations measured by consumer air quality monitors and the pDR-raw (uncorrected mass) relative to reference mass concentration for ARD aerosol. The error bars represent one standard deviation.

Figure 5

Fractional number (dN/N_T) and mass concentration (dM/M_T) by size measured for A) Salt; B) Welding fume; and C) ARD