# The Impact of an Office Fire Combined with the Stack Effect in a Multi-Story Building
## 4 Conclusions  
The numerical study conducted in PyroSim (FDS) simulated a fire on the ground floor of a nine-story building, analyzing its impact on the airflow and smoke movement. Following the simulations conducted, it has been proven that a full-scale numerical model is indispensable for obtaining feasible and relevant results. The fire outbreak on the ground floor represents the least favorable scenario in terms of enabling an efficient and safe evacuation, as well as due to its detrimental impact on fire development and spread. * Temperature. It was observed that infiltration joints did not significantly contribute to the intensification of the stack effect compared to a fire. The fire intensified the pre-existing thermal draft effect in the building, with measurements at control points showing the temperature in the ground-floor stairwell increasing from an average of 20 \({}^{\circ}\)C to over 400 \({}^{\circ}\)C, while other apartments experienced minimal changes. Analysis of temperature variation during the fire (S2) revealed a significant increase in the stairwell, especially on the ground floor, without considerably affecting other apartments. The measurements highlighted that the temperature of the stairwell rose by approximately 100 \({}^{\circ}\)C, whereas the top-floor apartments saw an increase of only about 5 \({}^{\circ}\)C, confirming the localized thermal effects of the fire. Notably, the limited temperature increase on the top floor can be attributed primarily to the short duration of the simulation, which lasted only 4 min. * Velocity. Natural ventilation in the context of a fire outbreak within a multi-story building can become completely ineffective if a preferential pathway is established between the fire floor and the top level. The analysis of gas velocities within the building reveals that the fire significantly intensified the thermal draft effect, causing notable increases in air velocities at the control points. Although wind speeds have increased considerably, they do not pose a threat to the safety of occupants, as they do not dislodge objects and remain below the critical risk threshold of 20 m/s. The building's geometry and the positioning of monitoring points influenced the velocity distribution, with significant fluctuations observed in relation to temperature variations. For instance, air velocities in the stairwell exceeded 8 m/s during peak fire conditions, while velocities in apartments remained below 5 m/s. * Visibility. The study of visibility inside the building shows that, although smoke infiltrates the apartments through unsealed openings, visibility remains adequate for evacuation, except in critical areas such as the burning apartment, the stairwell, and the top-floor apartments, where visibility tends to zero. These differences are determined by air circulation and the size of ventilation openings, highlighting the need for additional sealing and ventilation measures to improve fire safety. Specifically,  
Figure 14: CO and CO\({}_{2}\) concentration in the air in P3. visibility dropped to less than 1 m in the stairwell and top-floor apartments, while other areas maintained visibility above 10-20 m, which was sufficient for safe evacuation. However, due to the building's structural limitations, occupants could not evacuate through alternative routes. This observation highlights a critical issue concerning the fire safety of building occupants, which warrants further study. * CO and CO\({}_{2}\) concentration. The results of the indoor air quality analysis indicate that, in the event of a fire, lethal concentrations of CO and CO\({}_{2}\) are rapidly reached within the building, critically affecting the burning apartment, the staircase, and the top-floor apartments. The study of indoor air quality highlighted a strong correlation between toxic gas concentrations and reduced visibility during fires.