This thesis deals with the optimization of ventilation in visitor mines. Such optimizations include several aspects such as economic and safety improvements. In order to determine if the ventilation in the mine has some errors, the ventilation networks of the existing mine will be captured. The ventilation simulation software VentSim was used on the one hand to capture the actual state of the mine and for further risk assessment. The mine is dominated by natural ventilation. For this reason, this work describes the basic literature how airflows through mines behave according to fluid dynamics, as well as the influencing factors to the concerning the ventilation in the mine with special attention to natural ventilation. On the basis of the survey data as well as through mine visits, a three-dimensional model was created with the help of this software. In this model the all elements, which are used for ventilation control have to be implemented as well. To determine the input parameters for the simulation, on-site measurements were performed. This on-site measurements included: The temperature in different mine levels for determination of the thermal gradient plus the humidity and the barometric pressure. These measures are afterwards implemented to get accurate simulation results. Furthermore, the cross sections and airflow speeds were also measured to determine the actual amount of airflow at specific time. Due to the fact of natural ventilation, also the parameters of the outer environment had to be determined time depending, because the temperature changes the whole day and as a result the airflow changes as well. Subsequently, the accuracy of the simulation was determined by comparing the simulated and measured values. On basis of this created model some further risk assessments can be done. One part, that have be done are Gas simulations. Due to the small amount of airflow, caused by natural ventilation, some risks can occur in the mine. For instance because of so less airflow in depending on certain conditions the ventilation can become insufficient to dilute dangerous gases under the needed threshold values. An important part is the quantification of gases and location of the emission for a precise simulation result. The simulation is used to estimate gas concentrations depending on various influencing factors. A common tool used as a part of a risk assessment in fire events are fire simulations, which are also provided by the software. Such simulations can be done in real time based on the created ventilation model. The idea was to simulate different fire event scenarios to show how the fire emission will spread through the mine. Afterward critical areas can be detected and the influence by using ventilation doors and fans to steer the airflow in fire events. Such simulations can be used as supportive tool in the planning of a rescue and evacuation concept. By mine visits and on the basis of the simulations, measures are now taken to improve the ventilation network in the mine.