Ventilation, Fans & Filters

**th3 d0n 89** · 07-05-2012, 05:01 PM

Getting ready to set up a first time grow and I've been looking at diagrams and such. I have a little bit of confusion as to where I should place my carbon filters, all of the diagrams I've seen have placed them on the extraction fan. This doesn't make sense to me because I feel like you would want to filter the intake air so that they're aren't any airborne ailments. The only reason I can think of wanting to filter the extraction is to mask smell.

The next question I have is regarding placement. Naturally my extraction would be at the top (heat rises), but I've seen diagrams with the intake at the top as well, which to me would screw up air flow because you wouldn't get any circulation at the bottom. In my mind the intake should be filtered and place at the bottom to bring clean cool air into the room and an extraction at the top hooked up to my light with/without a carbon filter, depending on if you care about smell or not.

Any advice would be much appreciated. Please let me know if my logic is correct or if I'm completely off my rocker.

**ChroniKz** · 07-05-2012, 05:09 PM

Yes you want the filter on the extraction to cover up odour. Make sure the air PULLS through the filter and not pushes.
Extraction - top
Intake - Bottom
Also if you are using an intake fan make sure your extractor is more powerful as you want Negative Pressure to prevent odour leak.

Im not the most experienced but hope this gives you a guideline.

**Metasynth** · 07-05-2012, 05:10 PM

Intake at the bottom...If yout want to filter particulate matter, you'll need an intake fan, and many people just use passive intake(no fan, just a hole) and negative pressure to get fresh air in the tent. If you decide to use an intake fan, you'll still need an extraction fan MORE powerful than your intake, or dial the intake back with a speed controller. Then you can just go to home depot or something and get a flat filter in the AC/Ventilation area for like 10 bucks, and put that over the outside of the intake hole, so the air is being sucked through it.

Yes, carbon filters are to mask smell, and if you somehow do not need to mask, smell, then you don't need one. Extraction fan at the top of the tent, pulling air out of the tent.

So to re-cap, intake at bottom, extraction at top, carbon filter for smell, cheap flat central AC filter for intake if you so decide. Intake fan less powerful, or dialed down with a speed controller, extraction more powerful maintaining slight negative pressure in the tent/room.

**th3 d0n 89** · 07-05-2012, 05:12 PM

what if the fans are equal

**Metasynth** · 07-05-2012, 05:15 PM

Speed controller to dial back the intake fan...I said that TWICE in my post above.

EDIT...Maybe you posted that before you read my post...if that's the case, my bad. Don't mean to be rude...Welcome to RIU! I'm an asshole, but we're not ALL assholes!

**nuskool89** · 07-05-2012, 05:20 PM

Just use a dust shroom for the intake without a fan. Then have an exhaust fan hooked up to your carbon filter pulling air through it and out your cab. Keep your intake hole smaller than outtake. Intake bottom left on one side, outtake top right on opposite side