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coal filter

Discussion in 'Grow Room Design & Setup' started by lorenzo08, Jul 1, 2008.


    lorenzo08 Well-Known Member

    can I make a carbon filter? I've found small containers of activated coal for aquariums at walmart. could this be made into an exhaust filter?

    what about small electronic air filters. how well do they work with the smell? the air filter I have has an ionizer in it as well. what if I place the filter in
    a buffer box inside the exhaust?

    how well would these 2 methods work for a 4x10 room? what if I use both methods together? I've been researching and brain storming, but hearing from someone with experience can be invaluable.

    KillerWeed420 Well-Known Member

    Carbon filters are definitely the way to go. Lots of different styles. I just built a new one made out of an old dresser. Just the top drawer with the bottom cut out and a furnace filter in the bottom of the drawer and then put in a couple inches of carbon. Have an inline 6" fan plumbed through the top of it.

    Attached Files:


    lorenzo08 Well-Known Member

    very nice idea. how well does it work for you? do you recommend pulling air up into the carbon or down into it? how long does it last before it needs changing? what actually happens when the carbon is "spent". does it just not absorb any more oders and lets them pass back out of the filter?

    RandyRocket Well-Known Member


    honkeytown Well-Known Member

    or you can build one of these...built it for 56 bucks from lowes....just lined the inside of the top with carbon filter material and taped it on...I also just threw the rest of the filter on the back of my box fan...the fan pulling air in holds the filter to the back and draws ait thru it...pretty damn simple...and it also works...

    materials BTW:

    50cfm bath fan
    5"x4" reducer
    4"x3" reducer
    5" universal cap
    duct tape
    extension cord

    Attached Files:


    lorenzo08 Well-Known Member

    I've looked around the forum and read up on different custom designs of carbon filters. here is what I've come up with in my own design:

    1. I first built a small box out of 1x6 wood I had laying around. I mitered the corners and glued/nailed everything to seal it air tight. I end up with a box with no top or bottom, 12 inches long, 6 inches wide, and about 5 inches deep.

    that's as far as I got so far, but here is what I have planned:

    2. I take a standard air filter from a furnace or central air system. any will do, (can't be fiberglass type) but I'm looking for one with good air flow. it's a cloth-like filter with a zig zag shaped screen under it. flatten out the filter/screen and make it a flat sheet shape. cut out a piece to fit the box. fold the edges around to the sides of the box and securely glue and staple the filter to the bottom and sides of the box.

    3. fill the filter with activated coal. I'm using coal from the aquarium section of walmart. spread out the coal evenly to cover the bottom of the box with an inch or 2.

    4. I'll be building a custom exhaust filter to set my filter ontop of and seal it with weather stripping.

    I've heard, once the coal wares out, it can be used longer by crushing the coal into smaller pieces, or bake it in an oven at 350F for 30 minutes. I'll also be using an ion filter to supplement my carbon filter. I'll post pictures when I finish it :-)

    bonz Well-Known Member

    to start with you cant use aquarium charcoal. it dosen`t hold the smell properly, has to be for air. the holes in aquarium charcoal is meant for a larger size particle and only last about 1 week.

    lorenzo08 Well-Known Member

    what about crushing and/or baking? or is there anything else that might help it work better?

    any idea what they do to aquarium coal that's different from air filter coal?

    bonz Well-Known Member

    they dont do anything. the way activated carbon works is that there is microscopic holes in the pieces that contain the smells or particles. the stuff you need has more holes per square inch and are smaller, so it holds more smells. the stuff for water has larger holes so the small smell particles go right through.
    i made a homemade filter and made that mistake and it only lasted a week.

    lorenzo08 Well-Known Member

    thanks for the info

    I have all the parts to finish the project, and it only cost me about $5, so I'll finish the project and give it a try anyway. don't have anything to lose. the area my exhaust will probably vent into has a very dirty smell, so that will help cover up any spell that does pass through the filter. I think my goal with the carbon filter and the ion filter is to have it working "well enough". if it fails, I'll be in search of better carbon.

    bonz Well-Known Member

    you should be able to get the correct charcoal at a hydro store or order online. good luck

    lorenzo08 Well-Known Member

    what do you think of my fan idea. I've used a car radiator fan to pull fresh air into a bedroom in the summer. just need a strong 12 volt power supply that can handle a few amps for a period of time. I put a large resistor in series
    to give me high and low. low moves quite a bit of air and is quiet enough to sleep next to, and high moves a lot of air. I can also build a speed control circuit that is very efficient and flexible. this was part of my grow room plan. should be more then enough air movement for the size of my room. what do you think?

    RandyRocket Well-Known Member

    What is activated charcoal and why is it used in filters?

    Charcoal is carbon. (See this Question of the Day for details on how charcoal is made.) Activated charcoal is charcoal that has been treated with oxygen to open up millions of tiny pores between the carbon atoms. According to Encylopedia Britannica:

    The use of special manufacturing techniques results in highly porous charcoals that have surface areas of 300-2,000 square metres per gram. These so-called active, or activated, charcoals are widely used to adsorb odorous or coloured substances from gases or liquids.
    The word adsorb is important here. When a material adsorbs something, it attaches to it by chemical attraction. The huge surface area of activated charcoal gives it countless bonding sites. When certain chemicals pass next to the carbon surface, they attach to the surface and are trapped.

    Activated charcoal is good at trapping other carbon-based impurities ("organic" chemicals), as well as things like chlorine. Many other chemicals are not attracted to carbon at all -- sodium, nitrates, etc. -- so they pass right through. This means that an activated charcoal filter will remove certain impurities while ignoring others. It also means that, once all of the bonding sites are filled, an activated charcoal filter stops working. At that point you must replace the filter.

    from Howstuff works .com

    all activated charcoal is vapor based

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