Evaluation of two low-cost PM monitors under different laboratory and indoor conditions

Figures & data

Table 1. Specifications of the tested low-cost monitors.

Technical data	Foobot	Airvisual
Particle sensor	Sharp GP2Y1010AU0F	Airvisual AVPM25b
Sensor outputs	PM2.5	PM2.5 and PM10
Detectable particle size range (μm)	0.3–2.5	0.3–2.5
Sampling frequency	5 min	10 s or 5 min
Battery	No battery	Rechargeable Li-Ion battery
Data Storage	Remote storage	Internal and remote storage
Visual data display	No	Yes
Additional measured parameters	TVOCs, CO2, temperature and, relative humidity	CO2, temperature, and relative humidity
Cost ($)	199	269

Figure 1. Experimental setup in Aerosol Exposure Chamber at CH Technologies Inc. (Westwood, NJ, USA). For illustration purposes only.

Figure 2. Experimental setup in the Controlled Exposure Facility (CEF) at Rutgers Environmental and Occupational Health Sciences Institute (EOHSI).

Figure 3. Experimental setup for indoor testing of low-cost monitors during cooking.

Figure 4. Performance of low-cost monitors in the Aerosol Exposure Chamber when measuring different particles: (a) 0.72 μm PSL, (b) 2 μm PSL, (c) Arizona Road Dust (ARD).

Table 2. Summary of Pearson correlation coefficients (r) and linear regression parameters (intercept value, slope coefficient, and coefficient of determination R²) for the 5 min average PM_2.5 concentrations measured by Foobot and AirVisual units compared to TSI DRX, when challenged with 0.72 µm and 2 µm Polystyrene Latex (PSL) spheres and Arizona Road Dust (ARD) (measurements in Aerosol Exposure Chamber [AEC]), nano-silver spray (measurements in the Controlled Exposure Facility), and particles resulting from cooking (measurements in an indoor environment).

Instrument	Data pairs	Intercept value ± standard deviation, µg/m^3	Slope coefficient ± standard deviation	r	R^2
(A) 0.72 µm PSL
F1	18	21.15 ± 7.77	1.51 ± 0.17	0.92	0.84
F2	18	37.53 ± 11.93	1.27 ± 0.26	0.78	0.60
F3	18	19.24 ± 10.52	1.61 ± 0.23	0.87	0.76
A1	18	–0.77 ± 2.02	1.02 ± 0.04	0.99	0.97
A2	18	–1.06 ± 1.62	0.98 ± 0.03	0.99	0.98
A3	18	–1.57 ± 1.59	0.98 ± 0.03	0.99	0.98
(B) 2 µm PSL
F1	15	6.55 ± 5.51	1.79 ± 0.25	0.90	0.80
F2	15	1.94 ± 4.31	1.54 ± 0.19	0.91	0.83
F3	15	2.97 ± 2.52	1.82 ± 0.11	0.98	0.95
A1	15	–0.54 ± 0.92	0.83 ± 0.04	0.98	0.97
A2	15	–1.19 ± 2.52	0.95 ± 0.11	0.92	0.85
A3	15	–0.65 ± 1.92	0.85 ± 0.09	0.94	0.88
(C) ARD
F1	15	9.40 ± 6.89	0.55 ± 0.05	0.96	0.92
F2	15	22.98 ± 6.58	0.36 ± 0.04	0.92	0.84
F3	15	13.34 ± 8.19	0.49 ± 0.05	0.94	0.88
A1	15	4.49 ± 3.03	0.36 ± 0.02	0.98	0.96
A2	15	–0.45 ± 4.07	0.37 ± 0.03	0.97	0.94
A3	15	1.29 ± 3.378	0.37 ± 0.02	0.98	0.95
(D) Nano-Silver Spray particles
F1	44	10.57 ± 0.55	0.09 ± 0.02	0.68	0.46
F2	44	5.83 ± 1.28	0.33 ± 0.04	0.82	0.67
F3	44	8.01 ± 0.58	0.34 ± 0.02	0.96	0.91
A1	44	0.51 ± 0.12	0.03 ± 0.00	0.78	0.60
A2	44	0.37 ± 0.07	0.02 ± 0.00	0.84	0.71
A3	44	0.34 ± 0.05	0.01 ± 0.00	0.55	0.30
(E) Particles from cooking
F1	17	15.00 ± 0.88	0.24 ± 0.01	0.98	0.97
F2	17	10.55 ± 0.83	0.23 ± 0.01	0.99	0.97
F3	17	10.64 ± 1.08	0.28 ± 0.01	0.98	0.97
A1	17	–1.47 ± 1.80	0.48 ± 0.02	0.98	0.97
A2	17	0.11 ± 2.08	0.53 ± 0.03	0.98	0.96
A3	17	–0.59 ± 2.08	0.48 ± 0.03	0.98	0.96

Table 3. The precision error of paired monitor.

Paired Monitors	0.72μm PSL	2.00μm PSL	ARD	Nano-silver Spray	Particles from cooking
F1 vs F2	0.31	0.27	0.23	0.31	0.23
F1 vs F3	0.26	0.17	0.20	0.20	0.19
F2 vs F3	0.22	0.20	0.27	0.23	0.16
A1 vs A2	0.24	0.16	0.19	0.29	0.33
A1 vs A3	0.20	0.16	0.16	0.47	0.30
A2 vs A3	0.22	0.15	0.16	0.34	0.36

Table 4. The coefficient of variation, CV (%), for Foobot and AirVisual when challenged with different aerosols.

Instrument	0.72μm PSL	2.00μm PSL	ARD	Nano-Silver Spray	Particles from cooking
Foobot	21.0	16.7	19.2	19.0	15.2
AirVisual	17.6	12.5	13.4	28.7	24.0

Table 5. The p-values resulting from the paired t-test of sensor pairs. *Significant difference (p ≤ 0.05).

Paired Sensors	0.72μm PSL	2.00μm PSL	ARD	Nano-Silver Spray	Particles from cooking
F1 & F2	0.65	1.16E-09*	0.10	0.16	2.47E-06*
F1 & F3	0.94	0.16	0.69	0.10	0.028*
F2 & F3	0.58	7.49E-04*	0.10	6.71E-05*	0.037*
A1 & A2	0.31	0.06	0.12	3.05E-05*	0.10
A1 & A3	0.09	0.60	0.12	1.22E-06*	0.69
A2 & A3	0.31	0.18	0.59	2.52E-06*	0.017*

Figure 5. The size distribution of particles produced by nano-silver spray and a cooking event as measured by Grimm Aerosol Mini WRAS 1371 (Grimm Technologies Inc, Douglasville, GA, USA).

Figure 6. PM_2.5 concentrations measured in the Control Exposure Facility after spraying a nanosilver product.

Figure 7. PM_2.5 levels measured in the indoor environment during cooking.