At present, the actual pollutant emissions under slag removal stage have not been fully considered in the ventilation of tunnel construction, greatly increasing the required air volume for tunnel construction and causing huge energy waste. On-site testing of CO concentration and wind speed was conducted based on a certain tunnel, the changes in CO concentration over time under different processes were studied, and the effects of engineering vehicle emissions and fan air supply on the distribution of CO concentration and wind speed in the tunnel were analyzed. The results show that: The CO concentration on the palm face remained basically unchanged within 25 minutes after blasting, about 200 mg/m³; During the slag removal stage, the CO concentration on the palm surface decreases linearly and reaches the standard limit (30 mg/m³) after 90 minutes of ventilation; The actual required air volume for tunnel construction during the slag removal stage is much lower than the standard requirements. As the supply air volume increases, the CO concentration in the return air section decreases exponentially. Based on the research results, an empirical calculation formula for CO concentration in highway tunnel construction ventilation is proposed, which takes into account the coupling effects of CO emissions and supply air volume.

For the fire smoke control of the interchange ramp connecting the main tunnel at both ends, the effect of the longitudinal induced air velocity, smoke vent size and fire source location on the top centralized smoke exhaust effect was investigated with the help of numerical simulation software FDS based on the Nanjing West Jianning Road Curve A ramp project. The results show that: the fire source is located in the middle of the ramp, the induced air speed is 1.0 m/s to ensure that the smoke does not "spread across the area", and the smoke control effect is better when the induced air speed is 1.5 m/s and the smoke volume is 150 m³/s; the smoke spread range in the ramp decreases with the increase of the smoke vent size, and when the smoke vent length to width ratio is 4 and the area. When the smoke vent aspect ratio is 4 and the area is 6 m², the smoke control effect in the ramp is better, and the overall smoke exhaust efficiency of the system is more than 98%; when the smoke vent aspect ratio is unchanged, the maximum temperature of the vault decreases with the increase of the smoke vent area; when the smoke vent area is unchanged, the maximum temperature of the vault increases with the increase of the smoke vent aspect ratio. When the fire source is located in the upstream or downstream of the ramp, the smoke exhaust air volume should be increased to at least 210 m³/s and the induced air velocity should be optimized.