Growbox pressure

I tried to set the ventilation with two fans (outtake (Blauberg TURBO E-100: 220 m³/h) & intake (S&P, TD160/100 silent 180 m³/h) but then I have a positive pressure and as I heard the positive pressure isn’t good, because the smell of cannabis can leak out of the box through tiny holes.
So I set negative pressure but with one passive intake.
Will i feel the smell if I set negative pressure through passive intake instead of a intake fan???
I have searched through the lot of related topic and i didnt find specific answer.

I hope you understand my question.

thank you

@bob31 @Countryboyjvd1971 @Fever

That’s a good question for @Countryboyjvd1971 he’s in HVAC in sure he can give you a solid answer @Ivan2309

With negative pressure you shouldn’t have to worry about the smell, since negative pressure means there is more air bein pulled out then pulled in. You shouldn’t smell it if you have a good carbon filter in the exhaust


ok, that’s good to hear!!! :relaxed:
thank you

@bob31 @Hawkeye_diesel

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I’m fairly sure anyway, let country chime in to make sure, he is the expert in hvac


I thought I did and that’s why I tossed cb at ya. But then I read Hawks response and realized, I didn’t.

As long as it’s negative pressure it will be fine. The thing with passive is you may not be getting good air in fast enough… it really depends on being able to strike a reasonable balance and depending on your individual situation you might need an intake fan.

And yep cb is the HVAC man!


My grow box is only 2x2x4. My exhaust pulls 140CFM from the top of the sealed box. Intake is a 3" filtered hole at the bottom. It creates a quite strong vacuum. Carbon filter takes all smells away. :sunglasses:.

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ok, I’m glad to hear that because the dimensions of my box are similar to yours.
It seems to me logically that negative pressure is pulling out of the box air also through the passive intake but I want to check it out about the smell.

@Ivan2309 you’ll be fine with the passive intake
As @OldStealth mentioned it’s the carbon filter that’s removing the smell
I only run my intake fan when I need to force more cool air into tent usually after I’m in flower and have a nice canopy
And in winter I never run them
You should get a speed controller for you fans as well so you can adjust speed and control temps and humidity A little better


Because the box is small, I can keep humidity and temperature pretty much controlled with the fan speed.:sunglasses:

My Rh averages 67, temperature around 77.:sunglasses:

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Thanks @Countryboyjvd1971 @OldStealth … I get it (passive intake)
I did not count on the temperature when I started growing, because this was my first grow evere and i started it in april. Now i realized that it is easier to control the temperature in winter
Temp now: 82,76: during a day…lights on

thanks a lot :relaxed:

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For sure it easier in the cool weather @Ivan2309
You can try changing light schedule to have lights on at night and off day time ? It may help with tent temps
I’m lucky in one sense I have my grow in my basement so it’s not temps but humidity I have to deal with need to run dehumidifier most of time or Ac
Or my grow room would be 80% humidity 9 months out of the year the other 3 I used struggle to keep humidity but havevit all worked out now lol

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i have already changed the schedule: 6 pm-12am :slight_smile:
so much to learn…:sweat:
I assumed things would go that way, with a lot of problems, but there’s a first time for everything…
I hope to succeed only thanks to ILGM and to your help guys.

@Countryboyjvd1971 @bob31 @OldStealth @Hawkeye_diesel

see you at the next question

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Holler if you need anythin


Same here. Mind you, I keep it very small scale.:sunglasses:


Here if needed brother just tag me