I grow in a closet as well right now. I simple open the bedroom doors which go outside (1st floor) and have the duct pipe blow lamp air inside the room. Seems OK. ABout 72-85 temps. It does smell up the place a bit. I usually air the place when i come home.

Building a proper grow closet now (4x5x7) and that'll vent lamp air from the top and plant air from the bottom to outside (hopefully this won't look too weird.