## 4 Simulation Results Analysis  
### Analysis Results of Case 1 (with the Emergency Stairwell in the Middle of the Corridor)  
The amount of toxic gases entering the emergency stairwell during the time residents open and close the fire door after a fire outbreak was analyzed. Figure 6 shows the variation in the amount of smoke over time for each case. In terms of the soot mass fraction, the cases without air curtains showed over 90% higher levels, and excluding those without air curtains, vertical air curtains demonstrated lower soot mass fractions than horizontal ones at the same wind speed. Figure 7 shows the average temperature and visibility distance of the smoke at different times in Case 1. Figure 7a indicates that in scenarios without air curtains, the temperature in the stairwell nearly reached 120 \({}^{\circ}\)C, while in scenarios with air curtains, it did not exceed 30 \({}^{\circ}\)C. In these cases, the average temperature was found to decrease by more than 70%. Moreover, visibility was below 5 m without air curtains, but it exceeded 5 m when the air curtains were operational, with vertical air curtains being more effective than horizontal ones. Figure 8 illustrates the vector velocity caused by air curtains when the entrance door was opened. After the fire door is opened, the vectors formed outside the stairwell by the air curtain show that the horizontal air curtain creates a rotating vortex at the door, whereas the vertical air curtain forms vectors directed towards the stairwell. This indicates that vertical air curtains are more effective at blocking smoke from entering the stairwell. Figure 5: Evacuation simulation modeling. (**a**) Overall view of evacuation simulation. (**b**) Evacuation simulation before stairwell fire door opens. (**c**) Evacuation simulation after stairwell fire door opens. Analysis of Case 2 (Where the Emergency Stairwell Is Located at the End of the Corridor with Its Wider Side Facing the Corridor)  
In Case 2, the emergency stairwell is situated at the end of the corridor with its wider side facing the corridor. Figure 9 shows the change in the smoke amount according to the scenario during the opening and closing times of the stairwell's fire door in Case 2. The soot mass fraction  
Figure 8: Vector velocity caused by air curtains when the entrance door is open. **(a)** Horizontal air-curtain vector, **(b)** vertical air-curtain vector. Figure 6: Comparison of smoke amount in Case 1. Figure 7: Time-based simulation results for Case 1. **(a)** Temperature. **(b)** Visibility distance. decreased by 49-80% in scenarios with air curtains compared to those without air curtains. Further, vertical air curtains were found to be more effective at smoke blocking than horizontal ones, and their effectiveness increased with higher wind speeds. Figure 10 shows the temperature and visibility distance during the opening and closing times of the stairwell's fire door for different scenarios. Figure 10 displays the temperature, which exceeded 140 \({}^{\circ}\)C in scenarios without air curtains. With air curtains installed, the temperature lowered to near or below the safety standards for human occupancy. In Case 2-H-35, with air curtains installed, an average temperature decrease of 65% was observed. Figure 10 displays the visibility distance, which was less than 5 m in certain cases, even with air curtains installed, owing to the structure of the stairwell. Therefore, to enhance visibility, additional scenarios, Case 2-V-35-2 and Case 2-H-35-2, with a wind speed of 35 m/s for vertical and horizontal air curtains were analyzed, where a visibility exceeding 5 m was achieved. Figure 11 for Case 2 shows the vector values of the flow resulting from the operation of air curtains in the stairwell. Figure 11 shows that with a horizontal air curtain and the stairwell walls closed, a circulating flow is created inside the stairwell, preventing smoke from being expelled when it enters.