General Discussion

And it's certified via instrumented testing to ensure no electronic signals can be randomly transmitted out along with access controls and doors, outside storage for personal electronics, ect...
And that's just a plain old classified space. A SCIF has even stricter requirements.
Now, there may be a "curtain wall" in a classified space, but that's typically considered a "no go" space around a specific desk for a TS terminal.
A curtain by the entrance of a small conference room does not make a classified space...