I found a product called ONA Block at a local hydro store about 5 months ago, and the stuff really works for killing odors. From what I read about it, it chemically changes the odors. I've been using it ever since, with NO carbon filter at all, and it works at least as well as the filters did.
Once the stuff dries out a little, it shrinks in its can, and you can cut off the top 1/4" or so and expose fresh material, I can get a good 3 months out of an $8 can.
Once the stuff dries out a little, it shrinks in its can, and you can cut off the top 1/4" or so and expose fresh material, I can get a good 3 months out of an $8 can.