ok....if your lucky enough to find a round bucket. Free
Buy one of those fans that Video has on his building page. 15 bucks.
Like a mesh screen. 5 bucks.
Activated carbon. 10 bucks.
Drill the holes out at the bottom not in the middle where it appears video has it. Somehow get the mesh screen halfway in the middle of the bucket. Pour in the activated carbon. Then cover the carbon with another layer of mesh screen. You'd need to improvise on how to keep it suspended. Then put the fan on the top of the bucket exhausting out.