How long lasts a carbon filter?

Discussion in 'Growing Marijuana Indoors' started by ihctoab, Sep 10, 2009.

  1. Hey guys

    I'm new here and I am in the process of getting my stuff togheter to start my first grow. I am really into DIY so I try to build as much as I can and buy only the essential things.

    I found some activated carbon on the web and I was about to order some to build an odor filter but I'd like to know how long before I need to replace the carbon. It would help me select if I need a 5 pound or a 10 pound bag (or more).

    I am building a 20 plant grow under a 1000 HPS in about a 8x8x7 room.

    Also how can I calculate the fan size I need ?

    Thanks alot!
  2. #2 yesicancancan, Sep 10, 2009
    Last edited by a moderator: Sep 10, 2009
    8x8x7 = 468 ft ^ 3
    Now you want to turn that over every couple of minutes... So your fan will need at minimum about 250 cfm. In reality though fans that can move that much air THROUGH a carbon filter are generally very loud, especially when running full blast. So unless you want a lawn-mower sound emanating from your grow, I would get a nice quiet fan (check the ones in my sig) that is rated for about 2x what you need, then use a speed controller to dial it down just until you get negative pressure in the room.

    With that size room and that many plants I would shoot for something the size of a Can33, or about 15-20lbs of carbon. It should last a year at least, assuming you use the activated carbon granules.


  3. Wow a 500cfm fan is expensive... Is a 250-300 CFM really that loud? It'll be in my basement so maybe if it's like 2 times louder than a bathroom fan I can handle it. If it's like a high pitched sound it's another story... Also, why do I need insulated duct? Can I use regular round metal conduct?
  4. You could go with a very quiet 300 CFM fan, and truth be told a 6" S&P (the kind linked in my sig) running at 3/4 speed is still quieter then a 6" vortex running 1/2 speed.

    I do not personally use insulated duct, but it would cut down on the sound.


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