According to the experience in tunnel and parking ventilation project and using professional stuff, ARA Co is presenting fire simulation and analysis by Pyrosim software.
PyroSim is the leading software for quickly and accurately working with FDS models. PyroSim is a graphical user interface for the Fire Dynamics Simulator (FDS). PyroSim helps you quickly create and manage the details of complex fire models.

PyroSim imports AutoCAD DXF and DWG files. When PyroSim imports a DWG/DXF file, it will treat all 3D face data as obstructions and all other data (lines, curves, etc.) as separate CAD data. The left image of the figure shows the DWG file face data and the right image shows the grid representation that will be used in the FDS analysis.