COM3D is a three-dimensional code for turbulent reactive flow simulations in complex 3D-geometries. The Favre averaged Navier-Stokes equations are solved together with different models for turbulence and chemical kinetics. COM3D employs different flow solvers. Advanced numerical procedures are provided to facilitate the grid generation for complex 3D computational domains. COM3D was validated on experiments performed on different scales, with and without chemical reaction. Generally good agreement was observed for the important physical quantities. The code was used for combustion analysis of different application problems, ranging from small-scale laboratory tests up to large-scale reactor containment calculations.