Santa Fe Dehumidifier Duct Kit, Return Only (4035646) is an add-on to these dehumidifiers: Advanced90 and Advanced120. Duct work is useful if you need to dehumidify an otherwise inaccessible area, pump air from one room to another or simply to hide the dehumidifier. This is a collar that attaches where the moist air goes into the dehumidifier. To duct into another room, you need to use a 10" or a 12" duct, sold separately.