In the course of the design of the CERN Large Hadron Collider collimation regions as well as of other locations where important beam losses are expected and that contain critical accelerator elements, the FLUKA Monte Carlo code is extensively used. The field of applications spans from energy deposition calculations, studies of material damage, and detector studies to shielding design and activation studies. Using the design of the passive absorbers as an example, this paper illustrates the simulation approach, defines involved critical quantities, and confronts the need for simplified and detailed simulations.