You would want and intake/exhaust fan to vent the room, and as far a the smell goes I have seen small can filters that work wonders when placed strategically in the room.
im not sure about the air purifier, but my grow is in a 3x3x7 closet and with a 400 watt hps it gets about 90 without fans, i put one fan in the back corner, to blow the hot air to my big fan thats turned away from the plants, and pointing out the closet. If you turn a fan's back tords the room it will suck out all the hot air... my room stays about 75-77 now hope that helped
possibly i am not really sure you can always try it but it gets really smelly after a while my first grow was so toxic you could virtually smell it next door or outside.
just dont answer the door to anyone unless you know who it is.
I have my own place and have three holes in the door and one through the ceiling. There is an intake for the light ventilation in the door that gets pushed through the light and out through the ceiling. There is also an intake and exhaust in the door for the closet air to go in and out of.
I have all fitted with black pvc pipe and elbows to keep unwanted light escaping, or getting back in.
Otherwise, if you rent, you could just jack up the door and buy a new one when you leave. Chop some holes in it and fit some ducting. You handy???