... channels which can allow untreated air through the system. And Housing Material is Galvanised steel ... Grow tent ,hydroponics,greenhouse air cleaning.etc.And we suggest you apply air filter together with ventilation fans ... fan, Grow tent, Carbon filter, Light reflector, Electronic Ballast, Heavy duty hanger, Flexible duct... Rope Ratchet Filter Hanger Activated Charcoal Air Purifier, Air Filter for ...