# Study on Fire Smoke Distribution and Safety Evacuation of Subway Station Based on BIM
## 6 Conclusions  
(1) Based on the example of a subway station, this paper optimized the station layout scheme by adding an ascending escalator and recombining all vertical traffic facilities, and it established a three-dimensional visual model of the station based on BIM technology;  
(2) PyroSim software is used to establish a subway station fire model. The time taken for CO concentration, smoke temperature and visibility to reach the critical values of danger under different ignition points is calculated and analyzed. It is concluded that the time taken for visibility in the station to reach its critical value of danger is the shortest and that the threat to safety evacuation is the greatest. In case of fire at the end of the station platform, the available safe evacuation time of four groups of stairs and escalators is 88 s, 123 s, 168 s and 181 s, in sequence. In the case of fire in the middle of the station platform, the available safe evacuation time of the four groups of stairs and escalators is 163 s, 95 s, 90 s and 117 s;  
(3) Using Pathfinder software to establish a subway station fire evacuation model, this study calculates and analyzes the safety evacuation time of people in subway station fire situations, and concludes that the safety evacuation time of people in different fire situations is less than the available safe evacuation time, that is, the optimized subway station layout can ensure the safety evacuation of people in the station. At the same time, under the condition of satisfying normal use, passengers can choose the nearest stairs or escalators for evacuation, and can re-plan the evacuation path according to congestion, which improves the service efficiency of the stairs and escalators and the emergency evacuation capacity of the subway station, which is more conducive to passenger evacuation;  
(4) The combination of BIM technology and simulation software can effectively improve the efficiency and fineness of simulation modeling, facilitate comparative analysis and research and help to improve the accuracy of the evacuation results and show the evacuation simulation process more intuitively. The research results can provide a reference for the optimization of safety evacuation designs of similar subway stations;  
(5) The types of people in subway stations are complex. In the process of evacuation simulation in this paper, the types of evacuation people have not been fully considered, such as whether there are people who evacuate in groups or who are not able to move. In the process of evacuation, the average speed is set according to the classification of people, but the average value cannot reflect the individual differences in the real scene. In the future, we can try to eliminate the impact of individual differences on evacuation results, and how to conduct evacuation research on individuals. In addition, because the structure of each subway station is different, it is necessary to further select different subway stations for research and analysis to draw a conclusion with a wider applicability.  
Conceptualization, N.Z. and Y.L.; methodology, Y.L. and N.Z.; software, Y.L.; formal analysis and investigation, C.Z., F.W. and M.N.; writing--original draft preparation, Y.L. and M.N.; writing--review and editing, N.Z. and C.Z.; funding acquisition, N.Z. and F.W.; resources, F.W. All authors have read and agreed to the published version of the manuscript.  
This work is sponsored by the open Foundation of the BIM Engineering Center of Anhui Province (Grant No. AHBIM20202 KF) and the fund of Research Project Supported by Shanxi Scholarship Council of China (Grant No. 2020-038).  
**Acknowledgments:** The authors acknowledge the financial support of the BIM Engineering Center of Anhui Province, the Shanxi Scholarship Council of China and the relevant organizations. The authors are grateful for the comments provided by the anonymous reviewers.  
**Conflicts of Interest:** The authors declare no conflict of interest.