Those blocks sure do dry up fast, even with just drilling a few holes in the top, I was hoping for like 8 weeks out of mine.... Not so much....
Carbon filters probably do work best for odor control though. I never used one, but have been in/near grow rooms where a carbon filter was being used, and there was no smell outside the tent. I was always lucky enough to live in a place where I didn't need to get rid of the smell, I exhausted into the attic, and that was all I needed to do.
Since then I have moved, and can't have the house smelling of weed. I only have a small grow, and a carbon filter + fan isn't practical for my situation, and someone suggested Ona, and I wasn't a believer until I tried it. It works, and works well, if you use the gel, or plan to keep buying the blocks at a fast pace.
I've also tried another odor control gel, it works good, but the Ona smells better. I have an ozone generator as a back up, but never had to use it for growing weed, I do run it for like 10 minutes after smoking, and expect people over that don't smoke. It works better than the Ona in my opinion. I just don't want ozone in my office, where my cabs are.
Gary is right about the gel also. USE IT. The blocks aren't good for shit. At least, not for me. The gel worked MUCH better. Also, why not build your own carbon filter? I did that for my first grow.