INVESTIGATION OF THE NATURAL SMOKE EXHAUST OF AN ATRIUM BY THE CFD METHOD by YANG BAI Thesis Supervisor: Prof. Lap Mou Tam Department of Electromechanical Engineering, University of Macau In the recent years, there are many large-scale buildings such as hotels, shopping malls, and university campus built in Macau. The atrium is often used in those buildings. In the modern cities, the performance-based method is more and more used to design and evaluate the performance of fire protection facilities. Since the Macau fire code has been using over twenty years, the performance-based design for large-space such as atrium was not included in the Code. Among all construction codes and regulations, the fire protection engineering is one of the most important sections. Due to the rapid development of building technologies and advancement of building material, the local fire code should be enhanced. In this study, the performance-based method for fire protection in USA, Mainland China, and Hong Kong was summarised. The performance-based method becomes popular and more feasible due to computational power, unlike years ago, can be achieved with relatively lower cost. Commercially available tools for fire simulation can now be found easily, Fire Dynamics Simulator (FDS) is one of the famous CFD software to simulate the fire scenarios. However, the usage of those tools requires sound knowledge in the area of fire engineering. In this study, the natural smoke exhaust vent of an atrium was studied by a numerical method. FDS was used to establish a CFD model. The performance analyzes of the smoke exhaust based on façade natural vent design. An acceptable mesh cell size was determined by the comparison of results from equations in NFPA 92B and model simulations. For evaluating the performance of the smoke control design, the different fire scenarios are simulated with changing external wind speed, number of vents, etc. The mesh cell size of 0.4 meters was first determined by the comparison of results from the equations in NFPA 92B and the results of simulations. After that, the results showed that the stronger wind resists the smoke out of the natural venting and the smoke descending rate and the plume temperature are increased by the stronger wind speed. Furthermore, the effect of the vent size on the smoke exhaust rate is observed. However, the exhaust rate is not linearly proportional to the vent size. The results can not only verify the applicability of façade natural vent to control the smoke out from the atrium but also provide a reference for the performance-based design for revising the local fire code in the future.