On a recent home inspection in Aurora Colorado, My company, Magpie Property Inspections inspected a home that was equipped with a Duct Booster like this one. A unit like this is designed to increase the flow of heated air in warm heating systems, or cooled air in air conditioning systems. In most cases, a duct booster’s size limits its use to individual rooms, not the main supply line. They can normally be mounted on round or flat ducts. They are frequently installed on a warm air duct of a gravity warm air furnace to provide heating for a basement area, or may also be helpful in moving treated air to a remote room or through long spans of ductwork. If you have a room or area of your home which is difficult to heat or cool, this might be a solution for you.