So you are having a problem with the marijuana odour and want to fix it so a priest can sit in the next room and not know you are the leading provider in your state for marijuana. Well its not going to work that good the home made jobs are not for the pro's but then again pro's can afford to go buy one The Shopping List 1 roll - ¼ hardware cloth - look in the wire and fencing sections of home improvement stores 1 - 4 to 6 aluminum duct adapter 2 6 aluminum duct end caps (actually, you need a 4 and a 6, but no one seems to carry a 4, so I made one by carefully disassembling a 6 end cap cutting the end plate down to 4, then re-assembling it.) 1 4 aluminum duct starter collar 2 pair of womans pantyhose, I prefer black because activated carbon is black and it wont look so crappy .it looks cool. 3 or 4 boxes good quality activated carbon for fish tanks. (The actual amount you need depends on how big you make your filter.) 2 or 3 4 stainless duct clamps (those worm gear hose-type clamps- I used 3) 2 or 3 - 6 stainless duct clamps (those worm gear hose-type clamps I used 3) 1 tube of high strength duct sealant/epoxy - sets up strong and seals really well - usually found in the same section of the store as the ducting a handful of batting material (cotton, etc look in the quilting or fabric section at wal-mart, etc.) Now for the Assembly Disassemble a 6 end cap by drilling out the rivets. Cut the end plate down to a 4 circle with tin snips, etc. Wrap the edging back around the end plate and cut it to length leaving a bit of overlap. Clamp the two pieces together and seal with the sealant, allowing it to dry overnight. You should be left with something that looks exactly like the 6 end cap, but is only 4 in diameter. Cut a piece of hardware cloth the length you want your filter and the appropriate width to wrap around the starter collar and end cap with a small bit of overlap. Wrap the hardware cloth around the end cap and starter collar and use a 4 hose clamp at the midpoint of the cloth to hold the 3 pieces together. Cut a section of pantyhose to make a continuous tube, and pull it over the 3 pieces you just assembled. Add a hose clamp to each end to hold the pieces firmly together. You should be left with something that looks like a 4 version of the above pic with out the reducer, of course. Insert the assembly you just made into the large end of the 4-6 reducer. It may take some force to get the starter collar to snap in properly, but it will. I then sealed the joint with sealant/epoxy. Cut another piece of hardware cloth the proper length and size to go around the 6 end of the reducer and the 6 end cap, plus a little overlap. Install it with a 6 clamp at the midpoint. Cut another tube of pantyhose and fit it over the outside of the unit. Be careful not to rip it or get a runner (heaven forbid!) Install the outer two hose clamps as in the pic. Loosen the end hose clamp and you should be able to remove the 6 end cap without the thing falling apart at all. Add a few inches of batting material to the inside of the unit at the reducer end .this area will not have any airflow anyway and the batting will take the place of some activated carbon, thereby preventing wasted carbon. Fill with carbon almost to the top, then top off with more batting. Replace the end cap and tighten the hose clamp. Hook up to your duct work and enjoy the odor-less-ness! The final product should look something like the picture below, sorry about the lack of step by step pics, but I do not need to make another one. One of these days I will get around to it. Carbon Scrubber This does work if you can follow directions if you can not follow the directions you should go door to door and ask people for money.