It circulates the air that collects in the plenum. It also draws fresh air into the furnace through a filter on the side of the housing. This is exclusive to gas furnaces, particularly high ...

The return-air plenum carries air from rooms back to the furnace to be heated. Gas valve: Regulates the pressure of gas ...

Plenum: designed to fit in a wall of a building and accommodate the plants. Removable plant trays: accommodate growth media, plants, lights, and a watering device. Back duct: combines multiple air ...