Abstract: This research focuses on a standard three-story underground transfer station in Beijing. Considering the different types of fires that may occur on the three-story underground platform floor, numerical simulations of fire smoke are carried out using the PyroSim software. These simulations cover various conditions, such as different fire source locations, heat release rates, and smoke exhaust modes. The study aims at exploring the control effects of diverse smoke control modes comprehensively on the fire-generated smoke in the platform floor, with the ultimate objective of achieving precise control of the fire smoke control system in the subway platform area. The results clearly show that the division of smoke zones on the platform floor of a standard subway station is conducive to the control of fire generated smoke and the safe evacuation. And for luggage fires on the platform floor, the mechanical air-make-up provided by the smoke exhaust fans within the platform floor smoke zone and the air-conditioning system of the concourse floor can prevent the smoke effectively from spreading from the platform level to the concourse floor through the stairways and escalator openings. When it comes to train fires, in addition to activating the platform floor smoke exhaust fans, it is also crucial to activate the track exhaust fans and tunnel ventilation fans to restrain the spread of smoke effectively from the platform floor to the concourse floor. Moreover, through the statistical analysis of the wind speed at the stairway and escalator openings, it can be seen clearly that for luggage fires on the platform floor, due to the relatively small scale of such fires, a local downward wind speed lower than 1.5 m/s at the stairway and escalator openings can still prevent the smoke effectively from spreading to the concourse level. For train fires, the smoke control mode can ensure that the downward wind speed at each stairwell meets the regulatory requirements while being as close as possible to 1.5 m/s, which is more conducive to the safe evacuation.

Key words: subway station, smoke control system, smoke control mode, numerical simulation, downward wind speed