Abstract: In order to get the critical time of fire ventilation for metro trains, the required safe evacuation time is obtained by using the
formula of safety evacuation time for metro accidents, and compared with the available safe evacuation time obtained by numerical simulation of fire. The results show that when the fire happens in the middle of the subway train stopping at section, and the HRR is 5,7.5,10 MW, respectively, the longitudinal ventilation and smoke exhaust system should be activated to organize the evacuation of personnel in the upwind direction; when the power of HRR is 5 MW and the wind speed of longitudinal ventilation is 2.0 m/s, the safe evacuation of personnel can be guaranteed by starting ventilation in
150~180 s; when the HRR is 7.5,10 MW, and the longitudinal ventilation wind speed is 2.4 or 2.6 m/s respectively, ventilation can be started at 120~180 s to ensure the safe evacuation of personnel.Therefore, the critical time of ventilation is 120 s when the fan changes from static state to accident state; the critical time of ventilation from operation state to accident condition is 90 s.

Key words: metro section, train fire, safe evacuation, critical ventilation time