DearArray,nThank you so much for getting back to me. I have resolved this and have successfully created three solid (Set as fluid) (2 ducts and fluid in the lecture hall) with the respective walls labelled using named selection. I have also extruded the round diffusers and Outlets as they were causing me a lot of contact issues in meshing which after doing so solved the issue. However as i moved towards the setup stage, Missing new zones issue showed up and caused a lot of undefined surfaces to appear in the zone section.nI should also mentioned that I preserved the duct bodies when I Boolean Subtract it from the cavity of the lecture hall. What would most likely be the cause of this issue?nHope to hear from you soon.nThank you.n