If i'm reading this correct, you are planning on using an existing vent to provide cool/heat and not a return vent.

If you want to prevent any backup of odors you need to keep a negative pressure inside the growspace. The only real way to do it is with an exhaust fan, which means treating exhausted air with a scrubber. A 3x5 space doesn't require a huge fan or anything, but you must maintain a negative pressure. If the pressure becomes positive it will push out through any imperfections in the seals around your room and door.

Try as we all might, i really don't think there is gonna be a way around this one.

If you could run portable ac and have a 100% seal, that's a different story. Just a whole different set of circumstances to deal with at that point that i'm too stoned to ramble on about.

Do a search for "noobs guide to growrooms" or something close to that. Great info on room set up in there:thumbsup:
irydyum Reviewed by irydyum on . Grow Room Questions About Heating/Cooling/Odor Control I am planning on enclosing a little cavity corner in my garage that will create a 3' x 5' room. It will be rather easy to connect it to my central heat/air but i worry about odor control. i have successfully used some very small ozone generators inside cabinets in the past. those along with exhausting through activated carbon worked very well. only one strain was ever detectable by smell. with that said i will definitely be using 1 or 2 of these small ozone generators. the room will Rating: 5