I’ve just finished building my own Air intake fan with a filter. Which I actually use for the aggressive air intake (in front of a AC Infinity axial fan @110cfm) and at the bottom of my “Veg” tent air intake. I have 2 grow spaces. 54"x 33"x 82" flower room & 36"x 20"x 63" grow tent for veg. I take air in through the bottom of the VeG tent.(That’s where it starts, & runs through the 1st filter) I’m then pulling that air in through yet another filter (incase of ANY unfortunate events) into my flower room through a Corbin filter and out the house. I’m actually thinking of adding a small/medium sized deep freezer as a drying/curing chamber(which I already have right where I need it in the basement) and running it through the same exhaust system. I’m just not sure IF it’s a good idea or not! Any thoughts?
Here’s some more pics to see what I use and what the final product looks like. I also want to note for anyone in the future
If your wondering what kind of filter you can use; As long as it’s “MERV 8” or higher Your covered and nothing will hurt your ladies that come through that vent! I am wondering what household fabrics are the best to use. I heard “Nylon stockings” and “Cotton” But I’m not sure. Anyway, I hope this helps someone
I’ve been using zip tied fabric pots on the end of 6 inch ducting.
Seems to work ok.
Best picture I have at the moment…
I like the idea of using cut up ac filters tough.
Ya, and out of 1 air filter I get like 12 filters my size. So Bamm… @3months/filter; that’s 3yrs of solid air filters for $14.00(Only cuz they were on sale) but honestly you can’t go wrong!
Does that filter block pollen?
I also zip tie fabric pots to my intake, got the idea from someone on here.
I’m pretty sure it blocks pollen! It blocks viruses and I think viruses are smaller that a pollen sac. Sorry about this edit
But I just went and read the package and “YES” it blocks any and all pollen!
Nice! I may need to make this upgrade myself!
Nice!
Another use…
I needed a passive intake on my hybrid box. Installed a 20×30 Merv13. Same as my house. Lol
Flapper of thin foam setup to lift when fan is on to allow flow.
That’s all great stuff!! 
You guys put this ‘old hippy stoner’ to shame!
I took an old cardboard box (2’ x 3’ x 1’) cut a 16" x 24" hole on one side and an 8" circular hole on the other. I glued a spare furnace filter (18" x 25" for me) over the large hole and a 3 ’ section of 8" flexi duct into the circular (I’d take a picture but the filter box is somewhat inaccessible ATM).
Cheers
G