I've stalked sites like this for a while but this is my first post so be gentle. I live in an apartment where my landlord changed my lease from smoking okay to no smoking but that just wont do. I looked around and it seemed pretty easy to make your own carbon filter. I went on eBay and ordered 5 lb. of pharmaceutical grade Granular Activated Carbon (GAC) for $35. Even though the listing said something about the size of each grain I didn't really realize how small the grains were going to be, about the size of roughly ground coffee. Off of Craigslist I scored 2 elicent AXC 150B-C inline fans for just 30 bucks each, they can go from around 100 to upwards of 200 online. I actually found that the large 6" opening pretty challenging and ordered a 6"-4" reducer which came after I finished making the fan anyways. I went and collected things around town and what I came up with was this; a random plastic jar and duct tape from a dollar store and a 1 gal. paint bucket, a 2 gal. paint bucket, a 2 gal. bucket lid (ended up needing 2), and paint filters that were made for the 1 & and 2 gal. buckets (I would recommend getting 2 of each strainer, they're cheap) from a paint store. The plastic container I found fit very snugly with the 1 gal. bucket over it. Over all the supplies cost about $11 + $35 for carbon so I probably only saved about $20ish vs buying a factory made one. I was hoping that 5 lb. of carbon would be enough for both fans but to fill it all the way you will see I had to mix some rice in with it as filler, wouldn't want any loose pockets where air would rush through. Of the GAC I think it might take 6-7 pounds to completely fill it up. My general theroy for drilling holes was this I felt like it would give me the most air passing through the carbon. I would advice doing this somewhere you can easily clean up plastic dust without it getting away into nature. Don't forget to wash your carbon before use, I understand it's dust is pretty bad to breath. I wore a dust mask during all the handling of unwashed carbon and drilling of holes. I did this part before I started taking pictures but you can see it wrapped in the duct tape closest to the fan and the head sticking out. The fan came with some screws that let me keep the plastic jar in place, along with duct tape to seal it fit well. --step 1: drill holes in 1 gal. bucket --step 2: drill holes in 2 gal. bucket --step 3: cut a hole in the cap so it can fit on the plastic jar, or whatever kind of tube/piping you have coming from your fan I only had a dremel at my disposal and I messed up the first lid. --step 4: Slip the lid onto the jar/tube, I secured and sealed it with more tape and a hose clamp under it --step 5: put the paint strainers over the out side of the small bucket (which will be there to keep carbon out of the fan and let air come in) and on the inside of the larger bucket. Next put enough carbon on the bottom of the big bucket so that the small one is level with the rim when sitting inside then pour enough carbon on the sides so it fills all the way up, shaking while pouring to ensure it is evenly spread out --step 5.5: push both filters into the opening of the inner bucket so there will be no leaking, the jar/tube will keep them together and make an even tighter fit --step 6: take all of this and with the bucket of carbon on the ground push them together so the lid fits on the outer bucket and the jar/tub goes into the inner one. Then just push around the rim to seal it up, the buckets make a very tight seal I'm not to worried about it comming apart. Voilà now you are done. My final product looks like this As you can see it has enough sucking power to hold a dollar to it but I do wish it had more even suck. I ended up putting a band of duct tape on the large bucket closest to the fan because it was sucking harder than any other spot and that helped even it out some -------------------------------------- Final thoughts: I'm not unhappy with my finished product, it was fun to make, saved me a few bucks and makes it so I can smoke inside. I am interested to see how it compairs to a professionally made one. It makes some noise but not enough to be heard from outside. I'm thinking of making a scilencer with a larger 5 gal bucket on the exaust end with egg crate on the walls of it, or an old fluffy blanket if I can't find any. If i were to make this again I might go for some sort of mix of the small grains of activated carbon with larger pelets. Since I now have a reducer to 4" I might just order one though because my costs were roughly the costs of a 4" carbon can although the 6" ones are a little more pricey Like I said there are a handful of these kind of DIY fan posts but I hope any commentary, pictures, or my process helped anyone. I'd love to hear how other people's fans turn out or if you feel like I should have done anything differently I'm open to criticism, or if you just want to tell me how awesome I am I'm open to that too. Have a good day and blaze on! And sorry for any fuzzy pictures at the end