I know that you can fit creatures inside the bag and that the bag has a limited amount of air, with part of the Bag of Holding's description reading
"Breathing creatures inside the bag can survive up to a number of minutes equal to 10 divided by the number of creatures (minimum 1 minute), after which time they begin to suffocate." (DMG, pg. 153-154)
However, the Air Genasi have the racial trait Unending Breath
"You can hold your breath indefinitely while you’re not incapacitated." (Player's Companion- Elemental Evil, pg. 9).
This would imply that an Air Genasi could casually sit in the bag for hours while holding their breath. If so, could a party in theory smuggle a group of Air Genasi inside a Bag of Holding?
I do want to note, however, that the Bag of Holding does not specify that a creature inside of the extradimensional space can try to force its way out, so would putting someone in there even be a good idea?