WOW, it wouldn't work for everyone, but for ductwork, I don't think I've seen a cheaper / easier / cleaner solution.
I'm curious to see how long such a small amount of carbon will last (it seems like a small amt to me, though I haven't used carbon yet).
I was going to wait until you ran it for a while to say how much I like it but hell, even if it didn't last the whole 3 months it'd be a snap to recharge it or just swap it out for another!
Definitely +Rep. Please keep us up-to-date on the lasting power!