PC fans don't really have the pressure to use a carbon filter effectively. On top of that, DIY carbon filters don't really work even for 1 plant. They work to an extent but the whole room will still smell. Your best bet is to buy a can style fan and a carbon filter and just attach them inside the room where the grow is and keep that room's door closed. You can also seal the smell in by taking packing tape, folding it a little less than half way over so theres still a sticky part and sticking it over all the cracks of the door.
another one I just remembered, that I haven't tried, is taking a bucket, putting ona jell in it and drilling holes a few inches from the bottom. Then you buy an appropriate size round fan and set it on top blowing downwards.