Common Culture Carbon Filter 4in x 12in + 4in Inline Duct Fan ComboCommon Culture carbon filter and inline duct fan combo for odor control The Common Culture Carbon Filter 4" x 12" 200 CFM uses activated granular carbon to scrub odors and airborne pollutants from your grow space, locking unwanted smells inside its dense carbon bed. As air passes through the 4" x 12" filter, odor causing molecules bind to the carbon, leaving cleaner, fresher air exiting the system. This compact carbon filter is ideal for smaller grow