10.1 Fire Dampers: Location, Ratings & Installation

Smoke & Fire Dampers is 6 percent of the 50-question M2 — half of Duct Systems (12 percent) and the largest single task in that domain. Duct construction, supports, and sealing is 603 and 604. This chapter is Section 607, which the 2024 IMC brands [BF] because it is the same rule set as 2024 IBC 717. Tab 607 facing IBC 717; do not invent a third “mechanical damper chapter.”

2024 IMC 603.7 is only the hand-off: duct-system penetrations of walls, floors, ceilings, and roofs, and air-transfer openings in those components, shall be protected as required by Section 607. 607.1 is the scope sentence: this section governs protection of duct penetrations and air-transfer openings in assemblies required to be protected. A 2-hour occupancy-separation fire barrier with a 20-by-12 supply through it is a 607 problem, not a mastic problem.

Listing, static versus dynamic, hourly rating

607.3.1: Dampers shall be listed and labeled. Fire dampers shall comply with UL 555. A shop-fab blade with a hardware-store fusible link is not a fire damper.

607.2.3 Static dampers: Fire dampers and ceiling radiation dampers listed for use in static systems shall be installed only in HVAC systems that are automatically shut down in the event of a fire. A static curtain damper is tested with the air off. If the rooftop keeps running — or if any plausible combination of open and closed dampers still pushes air through this opening — you need a dynamic UL 555 damper. Dynamic listings are marked for airflow (1,000-fpm increments, minimum 2,000 fpm) and closure pressure (2-inch w.g. increments, minimum 4-inch w.g.). A static damper in a live duct is the classic “it closed on the bench” fail.

Table 607.3.2.1 is two rows. Memorize it; do not invent a “match the wall hour-for-hour” rule:

A 2-hour fire barrier, shaft, or occupancy-separation wall takes a 1½-hour fire damper. A 3-hour fire wall takes a 3-hour damper. The damper rating is not 2 hours in a 2-hour wall.

607.3.3.1 Fire damper actuation. The primary heat-responsive device (almost always a fusible link) shall operate at approximately 50°F above the normal temperature in the duct, but not less than 160°F. In an IBC Section 909 smoke-control system the operating temperature shall be not more than 350°F. A 165°F link on an ordinary office supply is the ordinary product. A painted, missing, or wire-tied link is a 607.3.3.1 fail before you talk about angles.

Where 607.5 actually requires a fire damper

607.5 sends you to 607.5.1 through 607.5.7. Where an assembly needs both a fire damper and a smoke damper, install a combination fire/smoke damper or a fire damper and a smoke damper.

607.5.1 Fire walls. Ducts and transfer openings that IBC 706.11 even allows through a fire wall shall have listed fire dampers installed in accordance with their listing. 607.5.1.1: if that fire wall is also a horizontal exit, add a listed smoke damper at every such penetration.

607.5.2 Fire barriers — this is the occupancy-separation row. Ducts and transfer openings that penetrate fire barriers shall have listed fire dampers installed in accordance with their listing. Ducts shall not penetrate interior-exit-stair, ramp, or exit-passageway enclosures except as IBC 1023.5 and 1024.6 allow. 607.5.2.1: a fire barrier used as a horizontal exit also needs a listed smoke damper.

607.5.2 Exception (fire damper not required at a fire barrier) is three items, and you must hit every word:

1. The penetration was tested to ASTM E119 or UL 263 as part of the rated assembly.
2. The duct is part of an approved smoke-control system (IMC 512) and a fire damper would interfere.
3. The wall is penetrated by a fully ducted HVAC system, has a required rating of 1 hour or less, is not Group H, and the building is sprinklered throughout to IBC 903.3.1.1 or 903.3.1.2. “Fully ducted” means sheet steel not less than 26 gage (0.0217 inch) continuous from the air handler to the inlet and outlet terminals. Flexible air connectors are allowed only as (a) a nonmetallic connection from a duct to equipment in a mechanical room, or (b) a 603.6.2 connector from an overhead metal duct to a ceiling diffuser in the same room.

A flex trunk punched through a 1-hour tenant fire barrier is not Exception 3.

607.5.3 Fire partitions (corridor walls, dwelling-unit separations that are partitions, not barriers). Fire dampers are required unless, in occupancies other than Group H, one of four exceptions applies. The two you will be asked: (1) corridor walls in a fully sprinklered building where the duct is protected as a through-penetration under IBC 714; and (3) a steel duct not more than 100 square inches, not less than 0.0217 inch thick, with no openings that communicate the corridor with adjacent rooms, installed above a ceiling, not terminating at a wall register, with a 12-inch-long by 0.060-inch steel sleeve centered in the opening, 1½-by-1½-by-0.060-inch steel retaining angles on both sides, No. 10 screws, and rock (mineral) wool in the annular space. Exception 4 is the 1-hour-or-less, fully ducted, sprinklered, not-H cousin of the fire-barrier exception.

607.5.5 Shaft enclosures. Shafts that may be penetrated shall be protected with listed fire and smoke dampers installed in accordance with their listing. That is the default: both. Exceptions are written, not implied:

1. Fire dampers are not required where (1.1) steel exhaust subducts not less than 0.0187 inch (No. 26 gage) extend not less than 22 inches vertically in the exhaust shaft and an exhaust fan at the upper terminus is powered continuously per IBC 909.11 so airflow is continuously upward to the outdoors; (1.2) the penetration was E119/UL 263 tested as part of the assembly; (1.3) the duct is IBC 909 smoke control and a fire damper would interfere; or (1.4) the penetration is a parking-garage exhaust or supply shaft separated from other building shafts by not less than 2-hour construction.
2. In sprinklered Group B and R, smoke dampers are not required at kitchen, clothes-dryer, bathroom, and toilet-room exhaust openings that use the same 26-gage / 22-inch subduct / continuously powered upward fan package.
3. Smoke dampers are not required at parking-garage shafts meeting the 2-hour separation.
4. Smoke dampers are not required in IBC 909 mechanical smoke control where the smoke damper would interfere.
5. Fire dampers and combination fire/smoke dampers are not required in kitchen and clothes-dryer exhaust systems where dampers are prohibited by this code. That is the Type I grease-duct rule: 506.3.11 says fire and smoke dampers shall not be installed in grease ducts.

607.5.5.1: Do not install fire or smoke dampers in a shaft that must keep continuous upward airflow if closing the damper would kill that airflow. 607.5.6: fire-resistance-rated exterior walls that IBC 705.12 requires to have protected openings get listed fire dampers.

607.6.1 (horizontal assemblies): a 603 duct that penetrates a rated floor/ceiling and connects not more than two stories may skip a shaft if a listed fire damper is at the floor line (or the duct is protected under IBC 714.5). The three-story, 26-gage, 4-inch, single-dwelling-unit exception is a residential-stack rule, not a commercial trunk rule.

Installation is the listing, not “close enough”

607.2: Fire, smoke, combination, and ceiling radiation dampers shall be installed in accordance with the manufacturer’s instructions, the dampers’ listing, and 607.2.1 through 607.2.3. The IMC does not publish a universal sleeve gauge, a universal retaining-angle size (except inside the 607.5.3 Exception 3 sleeve recipe), or a “within 2 inches of the wall” sentence. Those numbers live on the UL 555 installation sheet that ships with the damper.

What the listing almost always shows, and what the M2 expects you to look for:

• A steel sleeve in the opening, with the damper fastened to the sleeve — not to the gypsum.
• Retaining angles on both sides of the wall (or as the one-side listing actually allows), screwed to the sleeve and bearing on the face of the assembly.
• Breakaway joints between the sleeve and the connecting duct so a collapsing duct does not yank the damper out of the wall.
• The damper in the plane of the assembly, or within the listed distance — not “as close as possible” two feet down the hall.
• Access large enough to inspect the blades and the link (taught with 607.4 in the next section). 604.8: duct lining shall be interrupted at the area of operation of a fire damper.
• 607.7: flexible ducts and air connectors shall not pass through any fire-resistance-rated assembly.

607.2.1: if a fire damper would interfere with required IBC 909 smoke control, use approved alternative protection. 607.2.2: hazardous-exhaust fire dampers go to Section 509, not a random 607 exception. 607.2.4.1: MEP controls shall not be run through a fire, smoke, combination, or ceiling radiation damper unless the manufacturer and the listing allow it.

Field fail — damper nailed through the blades. A curtain or multi-blade damper is “secured” with roofing nails or drywall screws through the closed blades into the sleeve, the link is painted shut, there is no retaining angle on one side, the duct is screwed hard to the sleeve with no breakaway, and there is no access door. The product may still carry a UL 555 label in the box. The installation is not the listing. 607.2 is the correction notice.

Field fail — missing access. The 1½-hour damper is buried above a hard-lid corridor with no door and no removable duct section. You cannot see the link, you cannot reset the blades, and you cannot tell whether someone nailed them. That is a 607.4 fail taught in 10.3; write it on the 607.2 inspection too.

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