Active Air Inline Carbon Filter, 8"x30"Description The Next Advancement in Carbon Air Filtration: Active Air Inline Carbon Filters are designed for maximum versatility in filter and fan placement. The traditional limitation of having the carbon filter inside the grow room has been eliminated. Unique Design: Unlike most carbon filters which are terminal in design, i. e., closed at one end and need to be at the end of the ducting line, Active Air Inline Filters have a unique design allowing