Table 2 The air quality standard of tunnel
From: Simulation and measurement of air quality in the traffic congestion area
| Averaging period | England | Norway | Australia | USA | Japan | Taiwan | |
|---|---|---|---|---|---|---|---|
| CO (ppm) | 15 min | 200 | 200 | 100 | 120 | 100 | 75 |
| NO (ppm) | 1 h | 35 | 15 | – | 10 | 25 | 25 |
| NO2 (ppm) | 1 h | 5 | 1.5 | 1.5 | – | – | – |