dual exhaust fan for window
if u can afford two exhaust fans, set one up as an inlet to bring in fresh air from the outside and displace the stale air on the inside with an exhaust fan.....if ur livin in a colder climate, i know this will make the place cold but thats the price u gonna have to pay if u wanna smoke inside
Not sure if your separate room has a door but if it does, u should obviously close it.
Block bottom of door to the hallway with blankets or whatever.....check outline of the door with a lighter or match when door is shut to see how bad the draft really is.....if its sucking flame to the outside u got it bad and if desperate enough u can get a thick sheet of plastic (which they use to cover drafty windows in the winter) and tape or tac it up to completely cover door. If you dont want to go to that trouble get a good fan that is low to the ground and can swivel upward and place that in front of door. The main thing is getting the smoke out of the place thru means other than hallway door.
in addition to stuff above, yankee candles work well and bytches love them so thats a win win
keep air filter clean and change filters when recommended, also keep fans free of dust and shyt (ud be amazed at how efficient a clean fan works)
the carbon filter (isolation filer) near the door i dont think is enough (ur better off with good weather stripping at the base of the door, shyt is easy and cheap to install)....the goal should not be to let any air escape thru the hallway door