plenum space
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Plenum SpaceTRANSCRIPT
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Plenum space
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Vertical section through a commercial building without aplenum airspace. When both the supply and return ducts areconstructed in this manner, it is possible to insulate the ductsand the dropped ceiling so that the upper airspace is notheated or cooled, increasing energy efficiency.
A commercial building with a plenum airspace.
A plenum created by accident can go unnoticed andbecome a fire hazard, due to cabling installed under theassumption that this will always be a nonplenum airspace.
From Wikipedia, the free encyclopedia
Not to be confused with Plenum chamber.
This article does not cite any references or sources. Please help improve this
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and removed. (February 2012)
A plenum space is a part of a building that can facilitate air
circulation for heating and air conditioning systems, by providing
pathways for either heated/conditioned or return airflows, usually
at greater than atmospheric pressure. Space between the
structural floor and the dropped ceiling or under a raised floor is
typically considered plenum; however, some dropceiling designs
create a tight seal that does not allow for airflow and therefore may
not be considered a plenum airhandling space.
Purpose [edit]
The cavity/plenum space is typically used to house the
communication cables for the building's computer and telephone
network; however, it has been proposed that the growing
abandonment of cable in plenum spaces may pose a serious
hazard in the event of a fire, as once the fire reaches the plenum
space the airflow present in the space supplies fresh oxygen to the
flame and makes it grow much stronger than it would have
otherwise been.
Recent testing by ASHRAE has shown that, while flame spread is
limited by accumulated cable bundles, other structural concerns
may still exist due to increased load on suspended components.
As plenum spaces are restricted from use as areas for storage,
the principle behind removal of abandoned cable is that regulated
removal prevents the use of plenum spaces as a storage area for
abandoned cable. In addition, no highvoltage powered equipment
is allowed in the plenum space because presence of fresh air can
greatly increase danger of rapid flame spreading should the
equipment catch on fire.
Note that diligence is required to make sure that a nonplenum
airspace stays that way. A nonplenum airspace can become a
plenum airspace by accident if the ductwork is disconnected and
not properly repaired and resealed. Ductwork disconnection can
occur due to building damage such as earthquakes, aging, or
adverse environment causing the metal to corrode and fall apart,
or simply negligence on the part of building contractors that leave
work unfinished. In all such cases, discovery, and repair of such
problems to eliminate unintended plenums is difficult due to the
hidden nature, limited space, and difficult access of most installed
drop ceilings. For highest fire safety, it is best to assume all dropceiling airspaces are plenums, whether or not they are
officially designated as one.
References [edit]
Categories: Heating, ventilating, and air conditioning
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