Table 2 Overall VOC concentration in underground subway stations before and after COVID-19 pandemic.
Line | Length (km) | Before COVID-19 in 2019 | After COVID-19 in 2021 | ||||||
|---|---|---|---|---|---|---|---|---|---|
VOC concentration (µg/m3) | VOC concentration (µg/m3) | ||||||||
Mean ± SD | Min. | Median | Max. | Mean ± SD | Min. | Median | Max. | ||
1 | 7.8 | 26.1 ± 19.9 | 8.5 | 16.1 | 60.7 | 91.7 ± 78.3 | 19.6 | 96.6 | 291.0 |
2 | 60.2 | 32.1 ± 37.7 | 4.0 | 20.6 | 216.0 | 83.0 ± 52.6 | 24.2 | 63.9 | 218.0 |
3 | 38.2 | 30.7 ± 28.2 | 1.5 | 23.2 | 124.0 | 64.4 ± 41.8 | 16.7 | 54.0 | 222.0 |
4 | 31.7 | 42.3 ± 61.8 | 8.3 | 29.1 | 291.0 | 70.6 ± 46.6 | 21.9 | 64.4 | 158.0 |
5 | 56.9 | 54.0 ± 85.7 | 6.1 | 30.2 | 478.0 | 115.0 ± 71.7 | 17.1 | 103.0 | 392.0 |
6 | 36.3 | 36.3 ± 42.3 | 7.0 | 23.9 | 261.0 | 124.0 ± 93.9 | 32.2 | 99.9 | 382.0 |
7 | 57.1 | 53.0 ± 82.4 | 3.6 | 26.0 | 415.0 | 95.1 ± 42.3 | 36.2 | 84.3 | 207.0 |
8 | 17.7 | 65.0 ± 134.0 | 4.6 | 19.0 | 566.0 | 155.0 ± 83.0 | 63.5 | 117.0 | 360.0 |
Total | 305.9 | 43.8 ± 69.8 | 1.5 | 24.7 | 566.0 | 99.9 ± 68.5 | 16.7 | 84.4 | 392.0 |
