Ducting  is  an  approach  to  air  management  that  uses  a  series  of  metal  or  plastic  pipe  to  carry  heated  or  cooled  air  from  one  place  to  another. A  duct  system  is  often  referred  to  as  Ductwork.

There are two types of ducts  :  active and passive. Ducts are naturally passive because they have no moving parts. Active ducts use fans to help move the air. In the data center, air cooled by a computer room air conditioner (CRAC) can be carried through ducts into the raised floor and forced into the data center’s IT space through perforations in the raised floor panels. The duct moves heated or cooled air around (such as above ceiling spaces) without spilling the air into other areas. Ducting is used in hot and cold aisle containment, which improves data center reliability and energy efficiency. It can be used to exhaust hot air from IT equipment into a dropped ceiling, which then acts as its own duct to move air back to the CRAC. Ducts can also direct cold outside air into data centers, with proper filtration for contaminants and accommodation for humidity control.

Typically, the air pressure differential produced by CRAC activity pushes the heated air upwards as the cooled air is forced into the space below it, helping to complete the cooling loop. Return ducts are typically located above server racks or at the raised exhaust point within a containment enclosure where heated air (which is less dense than cool air) rises and can be exhausted more easily. Fans are generally only used with a simple ventilating duct (not a CRAC) or if there is a specific need to enhance airflow.