Drawing

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K.3
Cable/Conduit Beam/Purlin Hangers/Hanging
Systems
Stud Wall Communication/
Low Voltage
Dry Wall Acoustical Miscellaneous Index
Sizing Information
Reference
Codes & Standards
Reference
type shall be installed in any duct, or shaft containing only such
ducts, used for vapor removal or for ventilation of commercial-type
cooking equipment.
(B) Ducts Speci cally Fabricated for Environmental Air.
Only wiring methods consisting of Type MI cable, Type MC cable
employing a smooth or corrugated impervious metal sheath without
an overall nonmetallic covering, electrical metallic tubing,  exible
metallic tubing, intermediate metal conduit, or rigid metal conduit
without an overall nonmetallic covering shall be installed in ducts
speci cally fabricated to transport environmental air. Flexible metal
conduit shall be permitted, in lengths not to exceed 1.2m (4 ft.), to
connect physically adjustable equipment and devices permitted
to be in these fabricated ducts. The connectors used with  exible
metal conduit shall effectively close any openings in the connection.
Equipment and devices shall be permitted within such ducts only if
necessary for the direct action upon, or sensing of, the contained air.
Where equipment or devices are installed and illumination is
necessary to facilitate maintenance and repair, enclosed gasketed-
type luminaires shall be permitted.
C) Other Spaces Used for Environmental Air (Plenums).
This section shall apply to spaces not speci cally fabricated for
environmental air-handling purposes but used for air-handling
purposes as a plenum. This section shall not apply to habitable
rooms or areas of buildings, the prime purpose of which is not
air handling.
Informational Note No. 1: The space over a hung ceiling
used for environmental air-handling purposes is an example
of the type of other space to which this section applies.
Informational Note No. 2: The phrase “Other Spaces Used for
Environmental Air (Plenum)” as used in this section correlates with
the use of the term “plenum” in NFPA 90A-2009, Standard for the
Installation of Air-Conditioning and Ventilating Systems, and other
mechanical codes where the plenum is used for return air purposes,
as well as some other air-handling spaces.
Exception: This section shall not apply to the joist or stud spaces
of dwelling units where the wiring passes through such spaces
perpendicular to the long dimension of such spaces.
(1) Wiring Methods. The wiring methods for such other space
shall be limited to totally enclosed, nonventilated, insulated
busway having no provisions for plug-in connections, Type MI
cable, Type MC cable without an overall nonmetallic covering,
Type AC cable, or other factory-assembled multiconductor
control or power cable that is speci cally listed for use within
an air-handling space, or listed prefabricated cable assemblies
of metallic manufactured wiring systems without nonmetallic
sheath. Other types of cables, conductors, and raceways shall
be permitted to be installed in electrical metallic tubing,  exible
metallic tubing, intermediate metal conduit, rigid metal conduit
without an overall nonmetallic covering,  exible metal conduit,
or, where accessible, surface metal raceway or metal wireway
NFPA 70; National Electric Code; 2011 Revision
(continued)