Ammm, I believe someone mentioned to tape up the vents? I really wouldn't advise that in case you forget. Strangely, they put vents there for a reason not just aesthetics. If you fall asleep in a small room with no vents, it is quite possible you will wake up choking to death. Or not, but just to be safe.
I second the essential oils suggestion, Olbas oil is especially good and helps clear a blocked nose.Good luck