Activated carbon is effective at removing harmful VOC's (volatile organic compounds). The most common VOC is chlorine which is often used to treat town and city water sources. It also adds to the finished distilled product creating the best tasting and purest water. This NSF-approved carbon filter is of the highest quality and probably the best price for the Megahome filters. Fore use with the Megahome countertop distiller. Store in a dry place prior to use. A 12-pack of activated-carbon filters is a full one-year supply (at 1 gallon per day).