smart group to find blank department in device inventory

If you know what the data should be, then you can create a smart group.
E.G. choose Building as Criteria, and Is Not, and add your first Building. Then repeat using OR for all of the rest of your Buildings. Whatever it then finds should no Building data. Handy tip for adding the Values, click on the 3 dots to the right of the Value box, it will show you the data you have set, and you can pick it from there too.
Building "Is Not" Value A
Or Building "Is Not" Value B
Or Building "Is Not" Value C

Buildings and Department will show up in Advanced Criteria when you make the smart group.

Not an option as we have 12 buildings and around 200 departments..   I've now found the solution.

Thanks

If you're specifically looking for records that contain nothing (are totally empty of everything) then search for that...

Department is ____
or
Building is ____

Don't put anything in the fields, leave them totally blank.

Just want to thumb this up. Totally the simplest way to go.