the cieling? My 5 yr old niece said that they can just look through the vents and see us. Ive lived here for 9 months. Could they have been spying on me the whole time? Im a little creeped out.
No, the vents (actually registers) in your ceiling would be connected to sheet-metal ducts that run between your ceiling and their floor. If they have any floor registers, they would also be connected to ductwork, but not in the same location. So there is no way they could see into your apartment.
could be possible but highly unlikely, if there was sufficient room between the cieling and thier floor for a duct system, and the hole in the duct would have to correlate with your register (line up),try sticking a coat hanger through it (straighten it out first), if you feel no resistance then your elements are lined up. if you hit something then no.