Just to get input I am going to rehash an old topic.

I am attempting to enforce a standard for the display of rise and drop symbols in both AutoCAD and Revit. Everyone seems to have their own idea on what items should look like, and claim that these are from industry standards. People seem to want full control over Rise and Drop symbols, this I am not a fan of, however I would like the symbols in Revit to conform to a standard...

I was wondering what standard you conform to. It seems that Revit conforms to SMACNA CAD Standards, 2nd Edition July 2001 (see attached) apart from the Yin Yang on round duct being ignored.

Please reply with which standard you are conforming to and if possible a link to the standard.

The use of Shading or dotted lines based on up and down duct seems to be a common theme, and I wonder where this comes from, other than people like it and consider it a standard.

As another question that maybe someone from the development team can answer... Is Revit using SMACNA as the driving standard for rise drop symbols? and if so, why isnt the Yin Yang available? it is available in piping, so it should be easy to include in the ductwork.