$30 DIY Carbon Filter (Design by Ryoko)


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Ryoko said:
Security is important to marijuana growers, and odors can lead the police straight to your grow room. There are a number of 'odor solutions' out there, but they can be quite costly. Here is a simple method you can use to build your own carbon filter. It will take you about half an hour to construct it, and it will cost $20 to $30 dollars.

Aside from its main advantage of being ultra cheap, this method is also very versatile. It utilizes the exact same activated carbon filters that are used in professional air cleaners, without paying the huge prices. It can be adapted to practically any ventilation system. You do not need any crazy tools to build this - anyone can do it.

For supplies, everything is easily available at a store like Home Depot. You will need the following:

1 activated carbon filter - ( found near humidifiers, air, and hepa filters )
1 small roll of aluminum screen
1 four inch ventilation end-cap
1 four inch duct connector piece
1 roll of duct tape

No tools are required. A pair of scissors and a measuring tape are all you need.


The carbon filter I purchased is a 'universal' replacement filter for HoneyWell air purifiers. Since I didn't pay the hefty price for a professional unit, I will cut this to size. It was originally 16" high and about 48" long, so I cut it right down the middle. When the first filter is expired, I will have a replacement ready to go.


The next step is to cut your aluminum screen to size. I chose aluminum because it will be strong, and will still allow good air-flow. You could substitute chicken mesh or something similar. Since my (cut) carbon filter is 8" high, the aluminum will be cut to 12". The carbon filter will go in the middle 8" of this screen, with 2" coming out of each end to connect to the duct pieces.


Now we will attach the aluminum screen to the duct pieces, with duct tape. (This might be the first time you have actually used duct tape on ducts!) Do your best to keep it straight as possible.


It will seem a bit flimsy at the beginning. Continue to wrap the aluminum screen around and around, taping it every few inches. You want it to hold firm.


After a few wraps it will be fairly sturdy, and able to hold its own weight. However, don't drive your truck over it! Treat her nice and gentle like a Christian schoolgirl.


The ends of your screen may have little strands of metal poking out, threatening to impale you. Add some more duct tape to cover this up and to finalize the DIY carbon filter. Soon it will be done.


Now it is time to wrap the activated carbon filter onto our device. Conveniently, the filter I bought came with a couple of velcro straps, so I used them to hold it on. This will be convenient to replace when the activated carbon is expired.


After she's all sealed up, throw on a bit more duct tape around the edges of the carbon filter, to seal up any gaps. Only tape over the edges, because you want the air to flow as easily as possible. Air does not flow through duct tape. Here is the finished product.


Time to hook her up to the grow room exhaust! In this case, it is being hooked to a 4" square duct. (That is why I used a 4" round to 4" square connector piece. You may need a different piece to suit your ventilation setup, but a million sizes are available.) Just slide her onto the vent, and tape it down nice and sturdy. Duct tape is your reliable grey friend.


After she is attached and fire up, things are looking good. It is working nice, hooked to a 60 CFM fan, and you can feel the air flowing out of it lightly. The fan was not slowed down too much, but obviously a carbon filter will add some back-pressure to your vents. I haven't tried this with a slower blower (under 60 CFM), but 60 CFM is not a lot.

I just hooked this up today, so I don't know how often I will have to replace the carbon filter. The box the filter came in says to replace every two or three months. It does seem to make a difference though. Outside the grow room does not stink like a skunk anymore. There is almost no smell at all, except the faint odor of duct tape adhesive. I'm sure that will go away after a few hours.

Using this method, everyone can now build their own activated carbon filter. Its quite easy, and you can build it any size you need, to fit any grow room and any type of duct. Could it get any better than that?

I made my own version of this tonight. I used PVC instead of metal ducting, and I based the design off of a combination of Ryoko's and mtnjohn's. It looks good, I'll be attaching it to the cab tomorrow. I can't really test it out yet, but I'm hoping it's good.



I love the aluminum screen...I wish I'd found that when I went out on my last hunt. All I came back with is chicken wire, which is such a pain in the ass when trying to cut smoothly as to not rip the pantyhose or whatever cloth you cover it with.

What's that carbon filter you're using? Is it like filter cloth with carbon particles embedded in it? How much does it weigh (just wondering how much carbon it contains, or more importantly, how much surface area there is available for stinky air to be exposed to)?

Good little filter you've got going on :)
Thanks for the post.


EDIT: That aluminum screen isn't the same stuff you use like on a screen window or door is it? It looks sturdier. Come to think of it, most new screen windows I've seen don't use metal...it's more fabricy. It's more flimsy and wouldn't hold up to what you've used that stuff for. Thanks again.
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Same screen you use for windows and stuff I think. You buy it by the roll, WalMart has the exact thing in the picture. It's not that sturdy, but once it's layered like 5 or 6 times it holds up well.

The filter is hard to describe, it's at WalMart as well, the box for it isn't sealed shut so you can take it out and check it out. It seems pretty solid, but air can pass through it. It's made to be used as an air filter, so I'd think it'd be up to the job. If it'll be enough, I don't know. I'll be testing it out with some Sour Diesel IBL, and from what I've heard you need some serious odor control for that stuff.


668, Neighbor of the Beast
Question for Bounty,

You know the dimensions of the carbon cloth you got? I found some
15.75 x 46.5 sheets for around $10 plus shipping and was thinking of going that route if I can make a larger filter.

Filter Cloth
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I apologize, the pictures are screwing up. Is everyone else not seeing all the pictures? The code for them hasn't changed at all, there seems to be an issue with the picture gallery. Or is it just me, and everyone can see the pictures just fine?

SomeGuy - These are 16"x45", and they cost $9.99 at the store. They might be the same one, but if you wanted to save money, go bulk and buy a whole roll. It costs 4x as much as these little ones do, and it's 5x the material. It also might be thicker too.

As a plus, you can make much larger filters with that because of the original size, but it seems to be the same type of material.
I built one of these very similar to the one shown in the DIY but it did very little to combat smell. Not sure why though. Switched to ONA with soil moist crystals and a fan, cheap and it works. But if someone could help me get the carbon one working I'd prefer that. I currently have the unit hooked up to a flexible duct and vented another room in the house but the smell comes out the other end just as bad as the room it was sucked from.
Do I want the fan to be blowing air into the carbon filter or pulling the air through it and sending it out the duct? Currently pulling air through it.


668, Neighbor of the Beast
Pulling air is more efficient than pushing it.

Did you seal up good? Any chance the air is by passing the material? I havent built one yet so I dont know how good its going to work. The original thread people were raving about it for small grows.

Thanks. About the same size and with shipping about the same price. The version I found was 3/8 thick.


I found this thread this mornin. Spent 25 bucks (would have been cheaper but they didnt have the right dryer vent adapter so i had to fab a different one to work) .By this afternoon my Stinky trees were completely under control. Unfortunately i didnt have enough room to make the fan pull through since i'm in a pc case but its still just dandy.

Thanks for posting this. I had tried to do this a few times before and had no luck.



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hell of a nice post there Bounty 29. Absolutely love the step by step pictures....nothing left to question,it's all right there!


Get two birds stoned at once
It probably wont use much of that carbon, it'll just flow where there is the least carbon.


Active member
For what it's worth, I saw one of these filters at HD and took it out of the box.It was still in plastic and folded, but the actual material is pretty thick, and from the outside of the bag the carbon looks spread pretty well throughtout the fibers. The only other carbon impregnated filters I've seen were the "WEB" brand filters and weren't suitable, the "honeywell" ones like in this tek appear to be much better.
I like your design. I've been playing around with the carbon prefilters myself. I finally solved my odor problem by placing a HEPA filter unit in the space and turning it on full blast. The HEPA should help prevent mold and fungi problems as well. I supplement with a masking agent such as incense also.


everything you can do helps. do you notice a difference bounty?
hey , a tip on the cloth or nylon, do a wrap of plastic sheeting over the screen or chix wire before you put the cloth on. put the cloth over the plastic and then pull the plastic out from under the fabric. works slick.

edit/ i meant to add that if ur usin nylons it helps to roll em up like like a hot sexy chic would unrollem to take em off. then you unroll em over the screen.
beats tryin to pull them all they way around the tube. later
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