I've flown my Air 2 through some large spaces, but there were few if any people around, and I didn't fly over or near them. Ken H. had prop guards on that drone, but the Air 2 did not. Sweating the whole time!
In the US at least, "national airspace"--and all the federal regulations that come with it--is only outdoors.
Do the FAA rules and regulations apply to a commercial UAS or drone operations conducted indoors ONLY?
No, Part 107 would not apply to operations conducted indoors. FAA rules and regulations apply to operations conducted outdoors in the National Airspace System (NAS).