Page 97 - 2018_IMC

DUCT SYSTEMS

steel having a minimum thickness of 0.0187 inch penetrates the ceiling of a fire-resistance-rated floor/
(0.4712 mm) (No. 26 gage). ceiling or roof/ceiling assembly.
2. The duct shall open into only one dwelling unit or Exceptions:
sleeping unit and the duct system shall be contin- 1. A fire-resistance-rated assembly tested in
uous from the unit to the exterior of the building. accordance with ASTM E119 or UL 263
showing that ceiling radiation dampers are
3. The duct shall not exceed a 4-inch (102 mm)
nominal diameter and the total area of such ducts not required in order to maintain the fire-
shall not exceed 100 square inches for any 100 resistance rating of the assembly.
2
2
square feet (64 516 mm per 9.3 m ) of the floor 2. Where duct and air transfer openings are
area. protected with a duct outlet penetration sys-
4. The annular space around the duct is protected tem tested as part of a fire-resistance-rated
with materials that prevent the passage of flame assembly in accordance with ASTM E119
and hot gases sufficient to ignite cotton waste or UL 263.
when subjected to ASTM E119 or UL 263 time- [BF] 607.6.2.1 Ceiling radiation dampers testing and
temperature conditions under a minimum posi- installation. Ceiling radiation dampers shall be tested
tive pressure differential of 0.01 inch (2.49 Pa) of in accordance with Section 607.3.1. Ceiling radiation
water at the location of the penetration for the dampers shall be installed in accordance with the
time period equivalent to the fire-resistance rat- details listed in the fire-resistance-rated assembly and
ing of the construction penetrated.
the manufacturer’s installation instructions and the list-
5. Grille openings located in a ceiling of a fire-resis- ing.
tance-rated floor/ceiling or roof/ceiling assembly [BF] 607.6.3 Nonfire-resistance-rated floor assemblies.
shall be protected with a listed ceiling radiation Duct systems constructed of approved materials in accor-
damper installed in accordance with Section dance with Section 603 that penetrate nonfire-resistance-
607.6.2.1.
rated floor assemblies shall be protected by any of the fol-
[BF] 607.6.2 Membrane penetrations. Ducts and air lowing methods:
transfer openings constructed of approved materials, in 1. A shaft enclosure in accordance with Section 713 of
accordance with Section 603, that penetrate the ceiling the International Building Code.
membrane of a fire-resistance-rated floor/ceiling or roof/
ceiling assembly shall be protected with one of the follow- 2. The duct connects not more than two stories, and the
ing: annular space around the penetrating duct is pro-
tected with an approved noncombustible material
1. A shaft enclosure in accordance with Section 713 of that resists the free passage of flame and the prod-
the International Building Code.
ucts of combustion.
2. A listed ceiling radiation damper installed at the 3. In floor assemblies composed of noncombustible
ceiling line where a duct penetrates the ceiling of a materials, a shaft shall not be required where the
fire-resistance-rated floor/ceiling or roof/ceiling duct connects not more than three stories, and the
assembly.
annular space around the penetrating duct is pro-
Exceptions: tected with an approved noncombustible material
1. A fire-resistance-rated assembly tested in that resists the free passage of flame and the prod-
accordance with ASTM E119 or UL 263 ucts of combustion and a fire damper is installed at
showing that ceiling radiation dampers are each floor line.
not required in order to maintain the fire- Exception: Fire dampers are not required in ducts
resistance rating of the assembly. within individual residential dwelling units.
2. Where exhaust duct or outdoor air duct [BF] 607.7 Flexible ducts and air connectors. Flexible
penetrations are protected in accordance ducts and air connectors shall not pass through any fire-resis-
with Section 714.5.1.2 of the International tance-rated assembly.
Building Code, are located within the cav-
ity of a wall and do not pass through
another dwelling unit or tenant space.
3. Where duct and air transfer openings are
protected with a duct outlet penetration sys-
tem tested as part of a fire-resistance-rated
assembly in accordance with ASTM E119
or UL 263.
3. A listed ceiling radiation damper installed at the
ceiling line where a diffuser with no duct attached

80 2018 INTERNATIONAL MECHANICAL CODE 
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