## 3 Numerical Results
### Temperature Variation Inside the Building  
The analysis of temperature distribution across the three fire simulation scenarios reveals significant differences both in the fire compartment and along the evacuation route. In scenario S2, a maximum temperature of 490 \({}^{\circ}\)C is observed, uniformly distributed within the fire compartment (as illustrated in Figure 6--S2 at T = 240 s). This distribution is explained by the additional air supply entering from the staircase, which is maintained at a higher pressure relative to the adjacent rooms, with air being introduced even on the lower level. This increased oxygen supply promotes intense combustion and elevated temperatures in the affected zone. In contrast, scenario S1 shows the lowest temperature in the staircase, with a maximum value of 57 \({}^{\circ}\)C recorded on the ground floor. This condition is particularly favorable from the perspective of the safe evacuation of occupants on the upper levels, as well as for firefighter intervention, by offering a thermally protected area. In scenario S0, a temperature of 378 \({}^{\circ}\)C is recorded at point T2 in the staircase, a value that compromises the possibility of safe evacuation through this route. By comparison, in scenario S1, the temperature at the same location (T2) remains between 53 and 57 \({}^{\circ}\)C, indicating significantly better thermal protection. In scenario S2, the temperature at T2 reaches 137 \({}^{\circ}\)C, placing it between the values observed in the other two scenarios. Therefore, scenario S1 is the most favorable in terms of evacuation conditions and intervention safety, due to its effective thermal control within the stairwell. Figure 7 presents the temperature distribution through the slice at Y = 5.75 m, from which the following conclusions can be drawn:  
Figure 6: Temperature distribution in the slice at Y = 2.00 m at times T = 240 s and T = 360 s.  
* In scenario S0, the stairwell acts as a vertical conduit for the propagation of hot gases, reaching temperatures up to 130 \({}^{\circ}\)C on the upper floors (T3) and 85 \({}^{\circ}\)C at location T4. The high vertical temperatures indicate an intense infiltration of smoke and heat, severely compromising evacuation conditions. * In scenario S1, where the stairwell is pressurized and the door is opened at 120 s, the most favorable thermal profile is achieved: temperatures remain at 20 \({}^{\circ}\)C at points T3 and T4, while only 80 \({}^{\circ}\)C is recorded on the ground floor (T2). This scenario demonstrates the effectiveness of pressurization in preventing the ingress of hot gases into the stairwell, ensuring a safe and functional evacuation route for occupants and emergency responders. * In scenario S2, although the stairwell is pressurized, the door opening at 60 s and the placement of the fan on the lower level reduces the system's effectiveness. Temperatures significantly increase on the ground floor, reaching 140 \({}^{\circ}\)C at T2, which considerably reduces vertical evacuation safety. While the upper floors remain at 20 \({}^{\circ}\)C, the thermal load from the lower part of the stairwell adversely affects evacuation. Therefore, scenario S1 offers the best thermal protection conditions within the stairwell, while scenario S0 is the least favorable. Scenario S2 indicates partial protection, compromised by the timing of door opening and fan placement on the lower level. These results highlight the critical importance of precise synchronization between pressurization, fan placement, and access control to the fire-affected areas in maintaining a functional evacuation route. Figure 8 shows the temperature variation recorded by a thermocouple placed at X = 3.25 m, Y = 2.00 m, Z = 1.7 m above the fire source in the three simulated scenarios (S0, S1, and S2), highlighting the influence of the door opening time and ventilation configuration on the thermal regime. In scenario S2, the early door opening at 60 s does not cause a sudden temperature spike but rather a gradual and apparently controlled increase.