... 300-1250mm 2.Carbon layer thick: 35mm, 50mm High Iodine Air Filter for Hydroponics Plant System *Carbon layer thickness: 35mm, ... prevents the formation of preferential channels which can allow untreated air through the system. And Housing Material is Galvanised steel & ... , including Grow tent ,hydroponics,greenhouse air cleaning.etc.And we suggest you apply air filter together with ventilation fans 4. ...