Table 1.
The median and range (1st to 99th percentile) of RMSE from 250 calibration runs from six co-location lengths (1 day, 1 week, 6 weeks, 1 month, 3 months, and 6 months) for five low-cost sensors. The median and range (min to max) of PM2.5, CO, NO2, O3, and NO reference concentrations were 7 (1–53) μg/m3, 199 (100 –2950) ppb, 5.5 (1–58) ppb, 32 (1–110) ppb, and 0.5 (0.1–136.5) ppb, respectively.
| 1 Day | 1 Week | 1 Month | 6 Weeks | 3 Months | 6 Months | |
|---|---|---|---|---|---|---|
| PM2.5 (μg/m3) | 44.9 (5.2 – 400) | 6.6 (3.1 – 18.3) | 3.4 (3.1 – 9.1) | 3.4 (3.2 – 7.9) | 3.5 (3.2 – 5.6) | 3.6 (3.2 – 3.7) |
| CO (ppb) | 4870 (196 – 28,580) | 437 (61 – 1,630) | 125 (57 – 231) | 98 (59 – 219) | 77 (57 – 135) | 76 (51 – 105) |
| NO2 (ppb) | 22.4 (7.8 – 1830) | 8.6 (4.1 – 21.8) | 6.1 (4.1 – 10.5) | 6.1 (3.9 – 8.7) | 6.0 (3.7 – 7.8) | 4.9 (3.6 – 7.6) |
| O3 (ppb) | 721.2 (15.2 – 10,100) | 50.8 (9.1 – 267.8) | 15.7 (8.9 – 27.1) | 15.8 (8.2 – 22.8) | 15.0 (8.4 – 23.0) | 10.3 (8.1 – 12.6) |
| NO (ppb) | 16.3 (4.2 – 624) | 7.5 (3.5 – 72.4) | 4.3 (3.3 – 6.2) | 3.5 (3.1 – 4.7) | 3.6 (2.4 – 4.1) | 3.2 (2.9 – 3.6) |