## 3 Results and Discussion  
The results of the unsteady simulations are presented minute by minute for the first 5 min after the fire broke out, as these are the most important minutes for the emergency evacuation of passengers from the subway station [48]. The results of the simulations after 10, 15, and 20 min are also presented to assess the effect of emergency ventilation and PSDs on the evacuation of hot air and pollutants and to have an overview of the emergency situation at the station throughout the simulation. The results are given in term of longitudinal and cross sections, as well as 3D images that predict the air flow, temperature, CO, and CO\({}_{2}\) concentrations in the area near the ventilation devices, the fire outbreak, and the PSDs. The temperature fields obtained during the simulations are presented in Figure 12 (minutes 1-4) and Figure 13 (minutes 5-20) for a cross section through the area of the fire outbreak, on the left side of it (direction of propagation for hot air and pollutants). It can be seen that the area of the subway train with the fire outbreak is missing because the temperature in this region is higher than the maximum temperature scale used to more clearly represent the temperature fields in these figures. The maximum temperatures in the fire outbreak region have values between 900 and 1100 \({}^{\circ}\)C, in accordance with the temperature levels determined experimentally in [49] for fires with similar HRR values to those in this study. On the other hand, it is worth mentioning the important effect of the PSDs on limiting the propagation of hot air into the subway station. It can be clearly seen that if PSDs did not exist, a large amount of hot air would reach the platform area and prevent the safe evacuation of passengers. The CO concentrations are given in Figure 14 (minutes 1-4) and Figure 15 (minutes 5-20) in the same cross section through the fire outbreak (with maximum values of 6450 ppm). It can be noted that the CO accumulates in the space between the subway train and the PSDs. Consequently, these results show once again the impact of PSDs in blocking the entrance of polluted air into the station. The CO\({}_{2}\) concentrations in the same region are shown in Figure 16 (minutes 1-4) and Figure 17 (minutes 5-20). It can be observed that, in the first minutes, CO\({}_{2}\) accumulates under the subway (maximum concentration: 77,000 ppm) as the density of this gas is higher than air density. Furthermore, the impact of PSDs to limit the penetration of pollutants into the station is even more obvious in this case, as the PSD system stops the spread of CO\({}_{2}\) at the entire system height. Finally, CO\({}_{2}\) is driven by the upward movement of air towards the ventilation devices above the train, following the same distribution pattern as CO.  
Figure 12: Temperature contours (\({}^{\circ}\)C)—cross section through the fire outbreak (minutes 1–4). Figure 13: Temperature contours (\({}^{\circ}\)C)—cross section through the fire outbreak (minutes 5–20). Figure 14: CO contours (ppm)—cross section through the fire outbreak (minutes 1–4). Figure 15: CO contours (ppm)—cross section through the fire outbreak (minutes 5–20). Figure 16: CO\({}_{2}\) contours (ppm)—cross section through the fire outbreak (minutes 1–4). Moreover, Figures 18-23 present the temperature, CO concentration, and CO\({}_{2}\) concentration through the door of the PSD system to the left of the fire outbreak; this is the place with the highest chance that the polluted hot air will enter the station. Figure 17: CO\({}_{2}\) contours (ppm)—cross section through the fire outbreak (minutes 5–20). Figure 18: Temperature contours (°C)—cross section through the door of the PSD system near the fire outbreak (minutes 1–4). Figure 19: Temperature contours (\({}^{\circ}\)C)—cross section through the door of the PSD system near the fire outbreak (minutes 5–20). Figure 20: CO contours (ppm)—cross section through the door of the PSD system near the fire outbreak (minutes 1–4).