I have an odorsok on the inside of my cab, and it works great. I have had it for 6 months now, and I am on my 2nd grow, and it still works good. After my 1st grow I just took out the carbon sheet that is on the inside of the odorsok and threw it in the dryer for 15 minutes, good to go!

The Odor Sok has a 12mm fabric of 20 nanometer fibers and should have twice the contact surface of a heavy carbon filter. Sometimes humidity covers the fibers and lets odors by but it works again when it is dried.
The absolute definite place to use it is on the intake. I put on on my intake pipe and any powdery mildew dissappeared. The Odor Sok blocks light from getting in or out like shutter and air only moves through it when the fans run. I heard about a garden over a main street getting visitors when odor got out when the fans weren't on.
The Sok is great for low intensity uses like tents, mom rooms, babies, drying areas, and scrubbing. Mash them in clean water and dry to reset them.
Making homemade filters is OK but there are different kinds of carbon and big differences between them. Remeber why you are buying a carbon filter and make the investment in your security. Phresh filters and the old Phat and Dragon Filters are the best. The new "pHAT" and phat hydro filters won the brand name in a law suit but arent the same. Too bad that kind of thing has to happen in hydro.

Did u cut up the filter? Not supposed to do that but if it works....?

Umm, sorry for the dumbass question, but why on earth would you put an odor scrubber on the intake (as opposed to the exhaust)? To keep the smell outside your grow room from getting all over your plants?

And why do you have powdery mildew anywhere near your grow room?