To export ductwork to an IFC file, use the Export One Area to IFC File command.
Ribbon: DM HVAC->3D-BIM-> Export One Area to IFC File
Pulldown Menu: DM HVAC->3D-BIM->Export One Area to IFC File
Select the alignment point area to export and enter a name and location for the file.
If you have ductwork in multiple areas on a drawing, use the Export Drawing to IFC File command.
To export multiple drawings, use the Export Entire Project to IFC File command.
These IFC files can be imported into Revit and used for collision detection with the architectural model.