Page 95 - 2018_IMC

DUCT SYSTEMS

2. Ducts are used as part of an approved smoke con- 3.5. The duct shall not terminate at a wall reg-
trol system in accordance with Section 513 and ister in the fire-resistance-rated wall.
where the fire damper would interfere with the 3.6. A minimum 12-inch-long (305 mm) by
operation of the smoke control system.
0.060-inch-thick (1.52 mm) steel sleeve
3. Such walls are penetrated by ducted HVAC sys- shall be centered in each duct opening.
tems, have a required fire-resistance rating of 1 The sleeve shall be secured to both sides
hour or less, are in areas of other than Group H of the wall and all four sides of the sleeve
and are in buildings equipped throughout with an with minimum 1 / -inch by 1 / -inch by
1
1
2
2
automatic sprinkler system in accordance with 0.060-inch (38 mm by 38 mm by 1.52
Section 903.3.1.1 or 903.3.1.2 of the Interna- mm) steel retaining angles. The retaining
tional Building Code. For the purposes of this angles shall be secured to the sleeve and
exception, a ducted HVAC system shall be a duct the wall with No. 10 (M5) screws. The
system for the structure’s HVAC system. Such a annular space between the steel sleeve
duct system shall be constructed of sheet steel not and the wall opening shall be filled with
less than 26 gage [0.0217 inch (0.55 mm)] thick- rock (mineral) wool batting on all sides.
ness and shall be continuous from the air-han- 4. Such walls are penetrated by ducted HVAC sys-
dling appliance or equipment to the air outlet and tems, have a required fire-resistance rating of 1
inlet terminals.
hour or less, and are in areas of other than Group
[BF] 607.5.2.1 Horizontal exits. A listed smoke H and are in buildings equipped throughout with
damper designed to resist the passage of smoke shall be an automatic sprinkler system in accordance with
provided at each point that a duct or air transfer open- Section 903.3.1.1 or 903.3.1.2 of the Interna-
ing penetrates a fire barrier that serves as a horizontal tional Building Code. For the purposes of this
exit. exception, a ducted HVAC system shall be a duct
system for conveying supply, return or exhaust
[BF] 607.5.3 Fire partitions. Ducts and air transfer open-
ings that penetrate fire partitions shall be protected with air as part of the structure’s HVAC system. Such
listed fire dampers installed in accordance with their list- a duct system shall be constructed of sheet steel
ing. not less than 26 gage in thickness and shall be
continuous from the air-handling appliance or
Exception: In occupancies other than Group H, fire equipment to the air outlet and inlet terminals.
dampers are not required where any of the following [BF] 607.5.4 Corridors/smoke barriers. A listed smoke
apply:
damper designed to resist the passage of smoke shall be
1. Corridor walls in buildings equipped throughout provided at each point a duct or air transfer opening pene-
with an automatic sprinkler system in accordance trates a smoke barrier wall or a corridor enclosure required
with Section 903.3.1.1 or 903.3.1.2 of the Inter- to have smoke and draft control doors in accordance with
national Building Code and the duct is protected the International Building Code.
as a through penetration in accordance with Sec- A corridor damper shall be provided where corridor
tion 714 of the International Building Code.
ceilings, constructed as required for the corridor walls as
2. The partitions are tenant partitions in covered and permitted in Section 708.4, Exception 3, of the Interna-
open mall buildings where the walls are not tional Building Code, are penetrated.
required by provisions elsewhere in the Interna- A ceiling radiation damper shall be provided where the
tional Building Code to extend to the underside ceiling membrane of a fire-resistance-rated floor/ceiling or
of the floor or roof sheathing, slab or deck above. roof/ceiling assembly, constructed as permitted in Section
3. The duct system is constructed of approved mate- 708.4, Exception 2, of the International Building Code, is
rials in accordance with Section 603 and the duct penetrated.
penetrating the wall complies with all of the fol- Smoke dampers and smoke damper actuation methods
lowing requirements: shall comply with Section 607.5.4.1.
3.1. The duct shall not exceed 100 square Exceptions:
2
inches (0.06 m ). 1. Smoke dampers are not required in corridor pene-
trations where the building is equipped through-
3.2. The duct shall be constructed of steel not
out with an approved smoke control system in
less than 0.0217 inch (0.55 mm) in thick-
ness. accordance with Section 513 and smoke dampers
are not necessary for the operation and control of
3.3. The duct shall not have openings that the system.
communicate the corridor with adjacent 2. Smoke dampers are not required in smoke barrier
spaces or rooms.
penetrations where the openings in ducts are lim-
3.4. The duct shall be installed above a ceil- ited to a single smoke compartment and the ducts
ing. are constructed of steel.

78 2018 INTERNATIONAL MECHANICAL CODE 
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