Carbon filters are the most common way indoor gardeners to keep unwanted odors and scents from overpowering their gardens. These filters work by trapping odor causing molecules on the porous surface of activated carbon, which is finely packed into the metal cylinder for longevity …and ease of use. Carbon filters come in many sizes, and the bigger the flowering area, the bigger the carbon filter must be! HTG Supply carries carbon filters from the closet hero all the way up to commercial air filtering applications.