The MEP Modeler add-on allows us to run collision detection between the MEP and the structural elements. Run Collision Detection (Design/MEP Modeling/Detect Collisions or use the Toolbar shortcut). Rolldown the MarkUp Tool entries for both levels. Click on some of them to show the collisions, stop when the whole bottom slab is highlighted. Click the eye to remove highlights. Currently there are 18 clashes, which seems to be too much. What could be the problem here? The ducts are located in the air gap above the suspended ceiling. The ceiling, the air space and the load-bearing slab were modeled as one composite slab.