Supply air, return air, and outside air for heating, cooling, or evaporative cooling duct systems
constructed of metal shall comply with SMACNA HVAC
Duct Construction Standards-Metal and Flexible or UL 181.
Exception: [OSHPD 1, 2, 3 & 4] See Section 407.4.1.3
Not permitted for [OSHPD 1, 2, 3 & 4] Concealed building spaces or independent construction within buildings shall be permitted to be used as ducts or plenums.
Exception: [OSHPD 1, 2, 3 & 4] See Section 407.4.1.3
Not permitted for [OSHPD 1, 2, 3 & 4] Concealed building spaces or independent construction within buildings shall be permitted to be used as ducts or plenums.
Materials
exposed within ducts or plenums shall be noncombustible or
shall have a flame spread index not to exceed 25 and a smoke
developed index not to exceed 50, where tested as a composite product in accordance with ASTM E84 or UL 723.
Exceptions:
Exceptions:
- Return-air and outside-air ducts, plenums, or concealed spaces that serve a dwelling unit shall be permitted to be of combustible construction.
- Air filters in accordance with the requirements of Section 311.2.
- Water evaporation media in an evaporative cooler.
- Charcoal filters where protected with an approved fire suppression system.
- Products listed and labeled for installation within plenums in accordance with Section 602.2.1 through Section 602.2.4.
- Smoke detectors.
- Duct insulation, coverings, and linings and other supplementary materials installed in accordance with Section 604.0.
- Materials in a hazardous fabrication area including the areas above and below the fabrication area sharing a common air recirculation path with the fabrication area.
Electrical wiring in plenums shall
comply with NFPA 70. Electrical wires and cables and
optical fiber cables shall be listed and labeled for use in
plenums and shall have a flame spread distance not exceeding 5 feet (1524 mm), an average optical density
not exceeding 0.15, and a peak optical density not
exceeding 0.5, where tested in accordance with NFPA 262.
Nonmetallic fire sprinkler
piping in plenums shall be listed and labeled for use
in plenums and shall have a flame spread distance not
exceeding 5 feet (1524 mm), an average optical density
not exceeding 0.15 and, a peak optical density not
exceeding 0.5, where tested in accordance with UL 1887.
Nonmetallic pneumatic
tubing in plenums shall be listed and labeled for use in
plenums and shall have a flame spread distance not
exceeding 5 feet (1524 mm), an average optical density
not exceeding 0.15, and a peak optical density not
exceeding 0.5, where tested in accordance with UL 1820.
Loudspeakers
and recessed lighting fixtures, including their
assemblies and accessories, in plenums shall be listed and
labeled for use in plenums and shall have a peak rate of
heat release not exceeding 134 horsepower (hp) (100 kW),
an average optical density not exceeding 0.15, and a peak
optical density not exceeding 0.5, where tested in accordance
with UL 2043.
Discrete
plumbing, mechanical, and electrical products that are
located in a plenum and have exposed combustible material
shall be in accordance with UL 2043.
Ducts, plenums, or fittings of metal shall comply with SMACNA HVAC Duct Construction Standards-Metal and Flexible.
Existing metal ducts shall be permitted to be used where cooling coils are added to a
heating system, provided the first 10 feet (3048 mm) of the
duct or plenum measured from the cooling coil discharge are
constructed of metal of the gauge thickness in accordance
with SMACNA HVAC Duct Construction Standards- Metal
and Flexible. Existing metal ducts completely enclosed in
inaccessible concealed areas are not required to be replaced.
Accessible ducts shall be insulated in accordance with Section
604.0. For the purpose of this section, ducts shall be considered
accessible where the access space is 30 inches (762 mm)
or more in height.
Where gypsum products are exposed in ducts
or plenums, the air temperature shall be restricted to a range
from 50°F (10°C) to 125°F (52°C), and moisture content shall
be controlled so that the material is not adversely affected.
For the purpose of this section, gypsum products shall not be
exposed in ducts serving as supply from evaporative coolers,
and in other air-handling systems regulated by this chapter
where the temperature of the gypsum product will be below
the dew point temperature.
Factory-made air ducts shall
be approved for the use intended or shall be in accordance with the requirements of UL 181. Each portion of a factory-made
air duct system shall be identified by the manufacturer
with a label or other identification indicating compliance with its class designation.
[OSHPD 1, 2, 3, & 4] In
hospital building projects and all other health-care facilities,
including clinics and correctional treatment
centers, flexible ducts of not more than 10 feet (3048 mm)
in length may be used to connect supply, return or
exhaust-air terminal devices to rigid duct systems. Where
constant volume, variable volume or mixing boxes are
utilized, flexible duct of not more than 10 feet (3048 mm),
may be used on the inlet side for alignment. An internal
impervious liner shall be provided to isolate insulation
material from conditioned air.
Vibration isolators installed
between mechanical equipment and metal ducts (or casings)
shall be made of an approved material and shall not exceed 10
inches (254 mm) in length.
Corridors shall not be used to convey air
to or from rooms where the corridor is required to be of fire-resistive
construction in accordance with the building code
except where permitted by the building code.