the filter itself doesn’t care if you suck or blow.
they absolutely work better when you blow into them though.
Because you are creating a vacuum and pulling all stink out the room, including through all air cooled leaking light fixtures, door jambs, cracks, vent holes… and forcing it at the very last step into a carbon filter.
say you are pressurizing the hood with a fan before it, then pushing that into a carbon filter. Filtration is lost as the pressurized unfiltered air (and heat) exits the hood.
You get a grow big enough and you are building a room next to the grow just to house the filtration.
suck everything out of the room so you can see an incense or a puff get sucked in the door jamb or the vent holes. Blow that into your carbon filter. To reduce smell as much as possible set the fan directly on the carbon filter blowing in. The smell will disappear in minutes as long as the carbon filter works.
When used correctly, Quality carbon filters work very very well. They rely on them in space ships and jets.
Thanks for taking the time to help, appreciate it! You seem to know your stuff as well, nice. OK, I did the incense trick and my vaccum is working. You can see the smoke going into the cracks of my safe. If I'm hearing you correctly, running the fan first, filter second (blowing the air through the filter) works better? if this is true this is GREAT news. I'll gain a lot of needed headspace moving the big 4 inch filter out of my grow space... (the four inch filter is robbing me of 16 inches of space now)
This is very important information for me. If blowing works better than sucking though the filter, I'll redesign my grow cabinet. Thanks man!