Each ARCHICAD Building Material can be tagged for whether it should participate in Collision Detection.
Use the “Participates in Collision Detection” checkbox in the Categories and Properties panel of Building Materials (Options > Element Attributes > Building Materials).
If you uncheck this box for a Building Material, then those Building Materials in the model will be exempt from Collision Detection.
For example, if you are using composite elements or complex profiles with skins that model air gaps, you can uncheck this box for those Building Materials. In addition, in the Export Options dialog box of IFC Translation Setup, activate the checkbox “Export geometries that Participate in Collision Detection only”. This way, when the model is exported via IFC to the MEP application, only element parts having real geometry will participate in Collision Detection in IFC model-checkers and in ARCHICAD’s MEP Modeler. The MEP engineer can define systems (e.g. heating or ventilation pipes) without causing the program to signal collisions with air gaps.
If you have correctly defined the Building Material components of a model’s composite and complex profile elements, using the “Participates in Collision Detection” tag for air gap skins, then an MEP engineer can place pipes into these gaps, and the Collision Detection function of MEP Modeler will not find collisions for these elements.