For the dispersion of radioactive substances after release into the environment are sufficiently atmospheric dispersion models available that allow estimation of exposure in the near and far fields. For the emissions in buildings there are to date very little research. In this research project the interaction between flow and dispersion of pollutants to be investigated within buildings and the free atmosphere in coupled simulation models. For this, a literature search of existing simulation models to spread to an instantaneous release within a closed space volume (z. B. park, subway tunnel) should be placed with defined building openings basis. The aim of the project is to provide a simulation model that can determine both the spread by instantaneous release inside the building as well as the transport from the building. Here, the transport out of the building on the basis of relevant factors (explosive mass, specific radionuclides, various interiors, floors, window openings, etc.) should be investigated and these are coupled as a time-dependent volume source with an atmospheric dispersion model to ensure that exposure outside the building through the emission be able to determine within the building.