The diagram above shows how supply air is carried from the four make-up air units to all the floors of the building. This air is distributed through ducts and supplied through supply air registers to each of the apartments. The make-up air-handling units on the roof connect to the ductwork that supplies conditioned air through the apartments and returns air from the apartments back to the MAU. The make-up air units supply 100 % outside air and no recirculated air. Volume dampers and fire safety dampers are placed in the ductwork on each level. In case of a fire, the damper can close the duct and temporarily contain the smoke.