Once any chemical filter has all "sites" occupied, it will release less tightly bound chemicals in order to attach to more reactive chemicals. It does not matter whether you have purigen or carbon, the principles never change. We never see such a criticism of purigen because they are often the ones who start out by criticizing carbon that way in their ads, but they are not immune to that same effect. There is no such thing as a chemical filter that has an infinite capacity for absorbing or adsorbing chemical impurities. All chemical filters are eventually saturated and start releasing less reactive items in favor of more reactive items. It is simple chemistry and is not subject to the prejudices of advertisers or advertising campaigns.