Active Air Inline Carbon Filter, 6"x24"Description Next Advancement in Carbon Air Filtration: Introducing Active Air Inline Carbon Filters! These filters are installed inline which allows for maximum versatility in filter and fan placement. No longer does the carbon filter need to be located inside the grow room. Versatile Location: Traditional carbon filters are designed to be "terminal" they are closed at one end and must be at the end of the ducting line. Active Air Inline Filters can