Hey there wheatus The debate re:suck versus blow continues, but Ive tried em both in my present grow cab, & one is a clear winner Put your carbon filter as close as possible to the smell source ( IN ya grow space ), & suck that stench away as quick as possible. Did it the other way last year , with fan & cf in roof space.. no, no ,no.. not as good . Really noticed it ,after tending grow, I get a cloud of stink in my room.. Smell clears MUCH quicker when the CF is RIGHT above the plants, & if ya quick enuff, barely any smell leaks, & what does is cleaned quickly by being sucked thru the passive intakes. Depends on ya situation tho, but thats what has CLEARLY been the better option for my set-up Good luck, & be prepared to tweak thru things.. which may take a while take care