Fan/Filter Question & Budget Idea

I've never had need for fan or filter for growing yet but am gonna be using new indoor cabinet soon & wanted to clarify a basic premise - should a fan be placed at the end of a carbon filter sucking air thru it, or should fan sit at the beginning pushing air thru the filter?? Or does it not matter??


Also, any brief input on my budget carbon filter & fan idea would be appreciated; I wanna stay cheap & was gonna modify some of the DIY designs i've seen on here & do 2 x Pringles tubes filled approx. 80% with activated carbon, with filter pads at either end and use PC fans to pull the air thru. Can i ask, would a PC fan pull enough air thru this set-up to make it worthwhile?? I thought doing 2 coming out thru ceiling of same grow cabinet might maybe be enough, with just passive vent slits at bottoms of cabinet?? (cab size approx. 90cm x 60 x 50 - growing 3 plants max.)

Thanks for any input and comments in advance!

They're plenty of DIY tutorials on here if you look. I personally feel most DIY options are a false economy but goodluck, eventually i'm sure you'll come to this conclusion too.