Digitalisation is making its way into many areas of the construction industry, including tunnelling. With Building Information Modelling, also known as BIM, future large-scale projects, buildings and infrastructure designs are already being digitally modelled in the planning phase. It serves as a working method for handling construction projects. This makes it possible to subject building projects to variant studies as early as the design process. Safety-relevant issues, such as a sufficient supply of fresh air during the operation of road and railway tunnels in accordance with international guidelines, are considered in advance and already taken into account in the planning. Design optimisations are thus made possible at an early stage of planning. In this master thesis, the topic “Numerical modelling of the ventilation of tunnel facilities” is elaborated and examined with regard to its applicability to the complex tunnel research facility “Zentrum am Berg”. In the first section, the legal framework conditions for the operation of tunnel facilities and general technical aspects of various ventilation systems are presented. Dusts and gases that are harmful to health and are present in the ventilation flow of underground structures under construction are dealt with in a technical manner. The theoretical basics of numerical modelling methods are summarised within the scope of this work. The simulation is limited to a section of the “Railway Tunnel West”. The focus is on the illustration of the input parameters, as well as the discussion of the possibilities for representation and evaluation. The results of the research regarding suitable numerical software are discussed. With the help of measurement data from a simple ventilation test with natural ventilation and the CFD software from ANSYS Fluent, a model is built. The simulation data obtained in this way are examined and compared graphically with the real measurement data.