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Blow or Suck? Ventilation Question


New Member
Peace, Love and Hare Krishna you Groovy Freaks - lol

So my grow room build continues - received fan and filter today. Now I'm unsure how to proceed.

In the picture, you can see my "In Hole" bottom left. Air will be sucked in through this pipe. I plan on putting my "Out Hole" just to the left of where I have my light holders tied off (black cords).

My question is - should I filter as you see here, sucking air in through the filter and blow the filtered air OUT the hole? Or, can I place fan and filter in the next room and suck air out through the (planned) upper pipe and blow it out through the filter? In essence, do these filters work best when you suck air through them, or blow air out through them? Or does it matter?

My 'druthers are to put the fan and filter in the next room and force air out the filter - but you guys know which works best and that's what I'm after.



New Member
Imo for best smell coverage, it is best to have the fan in the grow room attached to the filter and blow filtered air out. this way any escaping air is already prefiltered also check your grow room has negative pressure. you can check this by simply holding a lit lighter at your inlet or vents and and watching the air draw the flame toward the vent. food for thought, my filter came wrapped on the out side with a washable prefilter but nothing on the inside. just my 2c


New Member
Thanks everyone for the advice - I need and appreciate it. Got my beans and final parts today and everything is set as far as the room goes. Doing light/temp checks now.

Unfortunately having my in/out ports opposite isn't going to happen the way my place is set up, although I can see how that would be ideal. I'm going to try blowing into the filter first - when my plants get stinky I'll know if it's working. If not, I can always put it into the grow room and prefilter.

Popping beans into water tonight, into dirt tomorrow AM. Got Northern Lights Auto Fems, advertised as great for beginners - but as Leonidas said, I'll put that to the test....I'll start a grow journal in the next day or so. Thanks to everyone for the advice!




Active Member
Hey ScurvyKnave,

I just finished building my first grow room too! :)

Some of the things that surprised me (others may not have had shared experiences, this is just what I wasn't expecting from a first timers pov) was: The need for multiple thermometers (as the temperature varied more than I expected from the floor to the light). A few days in I noticed my the oscillating fan I install was skewing some of the leaves (this was fixed by rotating the plants twice daily). The light-tighting process was more difficult than I anticipated as well, I stood inside the closed room/tent and noticed a few spots where light leaked in and because the inside was so reflective I believe this would have been an issue for the plants during their 'night time'.

Also (and very shamefully) I initially installed the fans the wrong way round (the extraction fan which connected after the carbon filter was actually blowing air into the tent). This was odd because I followed the instructions exactly- I only discovered it by placing my hand at the end of the ducting and feeling the air direction.

Anyway I hope that helps.

All the best friend

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