Most of us who smoke weed know of the classic paper towel roll stuffed with dryer sheets (here where I live its called a doob tube), but I've found that it doesn't really do much for the smell when I smoke kind bud (you could smell the lemon kush downstairs, outside, with the wind blowing). I needed a way to either mask or eliminate that dank smell so I could smoke in my dorm without the cops showing up. After reading about activated carbon filters for grow rooms, I had an idea. Why not make a cheap carbon filter to fit a "doob" tube? It was almost too easy. Here are the materials one needs: 1 paper towel roll, paper towels removed. 1 box dryer sheets, any scent. 1 rubber band. 1 container activated carbon for fish tanks. Where do I get activated carbon you ask? Easy! Go to your local Wal Mart. Head down to the fish/aquarium section and either find or ask where to find loose activated carbon for a fish tank filter. They make pre packaged filters, but what you wanna find is a clear plastic square container filled with loose carbon (charcoal). The one I found was made by Aqua-Tech and it only cost about 5 dollars. Now that you have the carbon, take your paper towel roll and rubber band 2 or 3 dryer sheets to one end of the tube. Then pour a good amount (1.5-2 inches) of carbon into the open end of the tube. Next, take 3 dryer sheets and, one at a time, stuff them into the open end of the tube. This is to keep your carbon from falling out. Now, whenever you smoke indoors, just exhale your smoke into the tube. The activated carbon acts as a scent eliminator, so even though you see smoke coming out of the tube, all you smell is freshness. Just change out your dryer sheets and carbon every 1-2 weeks, depending on how often you use the tube.