The TIAA MRT Tunnel Ventilation Fan (Exhaust) System is installed in TIAA MRT underground tunnel sections, which has three main functions: to ensure a safe environmental condition for the train to operate under normal mode; to ensure normal operation of the air conditioning system while the train is suspended inside the tunnel under congestion mode; to ensure a safe environmental condition for personnel evacuation under emergency mode.
When a train fire occurs in an under-ground station, the air conditioning / ventilation system will shut down immediately, leaving only the ventilation and exhaust system of essential equipment rooms and platforms turned on. On the other hand, to avoid platform wayside smoke from spreading into the station, air conditioning systems and fresh air TVF in the station will start to introduce external air directly to the platform to maintain steady and positive pressure in the station and also to prevent further spreading of smoke, which will enable save evacuation.
When a train fire occurs in the tunnel, the driver will immediately inform the operational control center (OCC) and the on-duty supervisor will determine the suitable evacuation method. If the evacuation method is determined to walk onto the track, the OCC will turn on tunnel lighting system and relevant TVF (exhaust) system in accordance to the evacuation direction. The settings of the turned-on fans are based on the operation mode table which will generate critical wind speed (2.5 m/sec, to avoid upstream smoke) to maximum air speed (11.2m/sec, to avoid impeding the evacuation) for personnel to escape under upstream wind to the nearest station, ventilation shafts, etc. and emit smoke to the opposite direction. The temperature of the escape routes should not exceed 60℃, and the smoke should not be spread to the track areas of non-accident tunnels or any adjacent station.
Another consideration regarding detrainment evacuation in tunnel is that this protocol is more difficult and dangerous. Therefore, only when the train is completely inoperative and the situation is endangering passenger safety will this method be triggered by the OCC. In general, the train will continue to operate to the nearest station for evacuation so that onboard personnel can utilize station facilities and implement a safer evacuation.