10.2 Smoke Dampers, Combination Dampers & Ceiling Radiation Dampers

A fire damper waits for heat. A smoke damper waits for a detector. Most M2 misses on this task happen when a candidate treats every rated wall as a fusible-link problem, or when a combination damper is hung in a smoke barrier with the actuator powered and no detector in the circuit.

Five listings — do not swap them

607.3.1 is the listing paragraph. Read every sentence:

• Fire dampers — UL 555.
• Smoke dampers — UL 555S.
• Combination fire/smoke dampers — both UL 555 and UL 555S.
• Ceiling radiation dampers — UL 555C, or tested as part of a fire-resistance-rated floor/ceiling or roof/ceiling assembly to ASTM E119 or UL 263.
• Corridor dampers — both UL 555 and UL 555S, and they shall demonstrate acceptable closure when subjected to 150 feet per minute velocity across the face during the UL 555 fire-exposure test.

A UL 555 fire damper is not a smoke damper. A UL 555C ceiling radiation damper is not a 1½-hour wall damper. A combination damper that only shows UL 555 on the label is not finished.

607.3.2.2 Smoke damper ratings. Leakage shall be Class I or II. Elevated-temperature ratings shall be not less than 250°F. UL 555S Class I is the tighter product — not more than 8 cfm per square foot of damper area at 4 inches w.g. Class II is not more than 20 cfm per square foot at 4 inches w.g. Class III exists in the UL standard and is not an IMC-legal smoke-damper class. The elevated-temperature mark is 250°F or 350°F; 250°F is the code floor, and 350°F is what many smoke-control shafts specify. Combination dampers (607.3.2.3) take the Table 607.3.2.1 fire rating and the 607.3.2.2 smoke rating.

607.3.2.4 Corridor damper ratings: (1) 1-hour fire-resistance rating, and (2) Class I or II leakage. That is a tunnel-corridor product, not a 3-hour fire-wall product.

Where 607.5 wants smoke — and how it closes

607.5.4 Corridors / smoke barriers. A listed smoke damper designed to resist the passage of smoke shall be provided at each point a duct or air-transfer opening penetrates a smoke-barrier wall or a corridor enclosure required to have smoke-and-draft-control doors. A corridor damper is required where corridor ceilings constructed as required for the corridor walls — IBC 708.4 Exception 3, the tunnel corridor — are penetrated. A ceiling radiation damper is required where the ceiling membrane of a rated floor/ceiling or roof/ceiling, used as permitted by IBC 708.4 Exception 2, is penetrated.

607.5.4 exceptions (smoke damper not required):

1. Corridor penetrations in a building with an approved IMC 512 smoke-control system where smoke dampers are not necessary to run that system.
2. Smoke-barrier penetrations where duct openings are limited to a single smoke compartment and the ducts are steel.
3. Corridor penetrations where the duct is steel not less than 0.019 inch thick and there are no openings serving the corridor.
4. IBC 407.5 Group I-2 Condition 2 smoke barriers where the HVAC system is fully ducted to 603, the building is NFPA 13 sprinklered, and heads are quick-response.

607.5.1.1 / 607.5.2.1 still add a smoke damper at a fire wall or fire barrier that is a horizontal exit. 607.5.5 still adds a smoke damper at a shaft unless Exception 2, 3, or 4 applies. 607.5.7 Smoke partitions: a listed smoke damper is required at each air-transfer opening through a smoke partition (ducted penetrations are a different 607.5 sentence). If that damper would interfere with IMC 512 smoke control, use approved alternative protection.

607.5 last sentence: where an assembly needs both fire and smoke dampers, provide combination fire/smoke dampers or a fire damper and a smoke damper. A shaft (607.5.5) is the everyday both-required location. A horizontal-exit fire barrier is the other.

607.3.3.2 Smoke damper actuation. The damper shall close upon actuation of a listed smoke detector or detectors installed to IBC 907.3 and one of these methods:

1. In a duct: detector inside the duct, or outside with sampling tubes into the duct, within 5 feet of the damper. No outlets or inlets between the detector (or tubes) and the damper. The detector shall be listed for the velocity, temperature, and humidity at that point. Other than mechanical smoke control, dampers shall close on fan shutdown where the local detector needs a minimum velocity to operate.
2. Above smoke-barrier doors: a spot-type detector on either side of the door opening, listed for releasing service if it drives the damper directly.
3. Unducted wall opening: a spot-type detector within 5 feet horizontally, listed for releasing service if it drives the damper directly.
4. Corridor wall or ceiling: the corridor smoke-detection system may control the damper.
5. Total-coverage detection in all areas served by that duct may control the dampers.

607.3.3.3 Combination actuation is 607.3.3.1 and 607.3.3.2 — heat and smoke. Combination dampers in smoke-control shaft penetrations shall not be activated by local-area smoke detection unless that detection is secondary to the smoke-management controls. 607.3.3.5 sends corridor dampers to the same two actuation sections. 607.5.4.1 repeats that smoke dampers close as 607.3.3.2 requires.

Field fail — combination damper not tied to a detector. The shaft collar has a beautiful UL 555 / 555S combination damper, 1½-hour / Class I / 250°F, powered open, with a fusible link in place — and the actuator pigtail is capped. There is no duct detector within 5 feet, no area-detection input, and no smoke-control panel. The heat side might still work. The smoke side is not installed. 607.3.3.2 / 607.3.3.3 is the notice.

Ceiling radiation dampers and corridor dampers

607.6.2 Membrane penetrations. A 603 duct or transfer opening that penetrates the ceiling membrane of a rated floor/ceiling or roof/ceiling shall have (1) a shaft, (2) a listed ceiling radiation damper at the ceiling line where a duct penetrates, or (3) a listed ceiling radiation damper at the ceiling line where a diffuser with no duct penetrates. Exceptions: an E119/UL 263 assembly that was tested without ceiling dampers; certain exhaust or outdoor-air ducts protected under IBC 714.5.2, kept in a wall cavity, and not crossing another dwelling unit or tenant space; or a duct-outlet penetration system tested as part of the assembly.

607.6.2.1: install the ceiling radiation damper per the assembly details, the manufacturer, and the listing — not “any pancake damper that fits the boot.” 607.6.2.1.1 Dynamic systems: if the HVAC is designed to run with fans on during a fire, the ceiling damper shall be labeled for dynamic systems. 607.6.2.1.2 Static systems: static ceiling dampers only in systems not designed to operate during a fire, unless a 5-foot duct detector, a room smoke-detection system, or a room occupant sensor that shuts the system down is actually provided. 607.3.3.4: the ceiling-damper actuation device operates at 50°F above normal duct temperature, not less than 160°F.

A ceiling radiation damper limits radiative heat through a membrane opening. It is not a substitute for a wall fire damper and not a substitute for a smoke damper in a smoke barrier.

Corridor dampers exist because some corridor ceilings are built like the corridor walls (the tunnel). 607.5.4 sends you to a corridor damper at that ceiling penetration. 607.3.1 and 607.3.2.4 are the product: UL 555 + UL 555S, 1-hour, Class I or II, proven to close at 150 fpm under the UL 555 fire test. Do not approve a plain ceiling radiation damper, or a 1½-hour wall combination damper that was never corridor-tested, at that hole.

607.7 still forbids flex through any fire-resistance-rated assembly. 506.3.11 still forbids fire and smoke dampers in Type I grease ducts; 607.5.5 Exception 5 is the matching 607 sentence.

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