The accuracy is the theoretical calculations for underground works turns more and more important for the effective design of emergency systems, like ventilation. That is why when some ventilation circuits need a special analysis one of the most advanced current technologies is used- the three dimensional simulation based on the Computational Mechanics of Fluids. Its more widespread name is CFD. The Uskudar metro station in Istanbul, Turkey, and the railway tunnel in Málaga airport, Spain, are two of the many cases that ZITRON has designed, evaluated and validated by means of this type of tool.