What i did is bought a hepa air purifier (Honeywell) at H.Depot for like 40.00$ took out the filter, bought activated carbon filter pads for fishtanks.
Nice thing is they're in mesh bags, still needed pantyhose so, covered the square carbon filters with pantyhose in the shape of the square filter. Put it in the unit, snapped the cover on, bingo air scrubber.
My closet is 4x8 walkin. door is closed during the day, while lights are off. Air filter running.
I get home, and lights on in the pm, crack/open the door air isn't as fresh as it could be, but smell is virtually gone. And plants do very good. I'll leave door open while lights on but if company coming over, close the door with the unit on and it's fine.
Pads at petsmart come in different sizes too from like 1"x3 up to like 5"x5" plenty big for the filter i needed.
You could also use this unit to pull air into the closet from under the door, cools a closet with heat issues.