I am in no way, shape, manner or form affiliated with EnviroKlenz! That out of the way, here's a blurb from their article:

"Activated carbon filters will remove chemical gasses. They work by adsorption, a process by which the toxic gasses are attracted to and stick to the carbon But there are problems with carbon filters. Since activated carbon simply collects toxic gasses and stores them, when the carbon becomes full of gasses, the gasses can release back into the air."

That is what I was referring to in terms of carbon not being a cure-all.