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Positive or Negative pressure in my grow tent?

Discussion in 'Grow Room Design/Setup' started by hollapainyo, Nov 27, 2010.

  1. I have a 2'x4' by 7' tall grow tent. My question is.... I am running a 400w HPS and i did not have enough $ for ventilation... So my tent has two good sized"flaps" that open on both sides of the tent at the bottom, all I did was open one flap and placed a box fan infront of it and turned it on high..... inside the tent i placed another fan blowing the same direction. The ten also has duct hole at both ends... i opened the duct hole on the opposite side of the box fans (the duct holes are at the top of the tent). When i close the tent up it turns into a ballon and there is a TON of air coming out of the exhaust hole. Is this considered positive or negative pressure ventilation..... and why dont people use this method..... it seems WAY cheaper and gets the job done.
  2. im pretty sure thats positive if it blows up like a balloon. you want the doors/sides of the tent to suck in when closed.

    for my tent i gave a inline fan pulling air out, and the only intake i have is the flaps that you were talking about. if smell is a problem for you, all that air blowing out through the duct holes etc will blow out some stinky air.
  3. Nah smell is not an issue cause the very first thing i bought was an ozone machine ( my whole apartment smells like a doctors office ). I guess what i was trying to get at was just as long as this method keeps the temp down its okay right? So i can avoid spending the extra coin on duct work and fans right? I just used what i had around the apartment and it seems to work fine. Anyone know the pros and cons of possitive pressure and negative pressure?
  4. common sense should tell your brain that negative pressure will suck air in which effectively doesn't let any "stinky" air out. Positive pressure would blow all of that stinky air out through every little hole or crease in the tent. Use ozone at your own risk, it crystallizes your lungs. A good carbon filter such as phresh or mountain air is a much better choice. I'm sure you'll make mistakes before you get it right. good luck.
  5. #5 hollapainyo, Nov 27, 2010
    Last edited by a moderator: Nov 27, 2010
    Okay after reading a ton of stickies I have learned im doing this ALL WRONG...... call me dumb i dont care im still new to this..... I cant quite wrap my head around the idea of how to set up a DIY inline fan with carbon scrubber... any help would be appreciated.
  6. I mean how to set up the ventilation in my grow tent:confused:
  7. The Scrubber is the first part of your chain, the fan is the last. I have a cooltube HPS light, so my chain is the following.

    Carbon Filter, 4" ducting from the filter to the one end of the cooltube. Then the cooltube. 4" ducting on the other end of the cooltube up to the fan, and out of the grow space.

    Make sure your Filter is strong enough for the fan's pulling power. If not, the fan will pull the air through too fast for the carbon filter to do its job and you will still have odor. But also make sure the fan is strong enough for the air exchange and heat removal you need.

    Good Luck. Peace. :smoke:

    You can see my setup in the Current Grow link in my sig. I have pics I put up when I made the change to the cooltube..
  8. I appreciate the help..... was starting to wonder if this thread would die out and i dont like to annoy anyone.... Thanks again
  9. Also just curious.... the pictures do not show where the fan is? Please have patience with me..... i grow for personal use cause i have ptsd and traumatic brain injury from iraq and i would rather smoke than take the pills the VA gives me and my brain doesnt process things quite like it use to.... not looking for a pitty party AT ALL i just wanted to stress that it takes me a while to read things and picture it in my head ya know.:smoke:
  10. I have a squirrel cage fan, and due to the small size of my grow tent, I could not for the life of me, figure out how to mount the fan on the inside. So the fan sits right on top of the tent., well on a shelf thats right above the tent. The ducting goes out the top of the tent, and connects to the inlet hole of the fan, right outside. You basically see the hole setup, run right up to the side of the fan.
  11. i have the filter mounted in, ducting going out and into the inline fan in the roof. if that makes sense to you
  12. I treat the heat and the stink as separate "problems".

    I have a 6" fan on a speed control for the Cooltube and a 4" fan on a speed control for the stink.

    You want negative pressure on the tent or you are gonna "leak" stink.

    I do not use the grow room air for lamp cooling.

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