I came across a video a couple years back with somebody washing the carbon and then re-activating it. Basically, he put it in a bucket and ran water through it to wash away all the crap (it looked nasty when he did it). After he washed it, he put it in a single use turkey tray and cooked it in his BBQ. The heating activates it and give you fresh carbon (at least that was the moral to the story). I have not tried it yet, like many things, it is on my list of experiments to do when I can get a spare moment. I just buy new ones whenever I have an especially stinky strain(s) that my older filters just can't contend with.