View & Edit 3D Revit Files Without Revit | AutoMEP
Checking one duct run in a Revit model usually means waiting for Revit to load. Upload the model to AutoMEP instead and it prepares a 3D view you can turn and zoom in the browser. From the same page you can describe a change to the model the way you would on a DWG.
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- Revit file foundation in the Version 1.1 release notes