1 Scope
NOTE This standard governs life-safety dampers installed at HVAC duct penetrations through fire-rated and smoke-rated building assemblies, including curtain-type fire dampers, multi-blade fire dampers, smoke dampers, combination fire/smoke dampers, and corridor dampers. (1.1)
NOTE Fire and smoke dampers exist to maintain the compartmentalization of a building when an HVAC duct breaches a rated barrier. A fire-rated wall, floor, or shaft is only as good as the protection at every opening through it; an unprotected duct penetration is an open path for fire and smoke to spread between compartments. The damper restores the rating of the assembly at the opening by closing automatically on a thermal or alarm signal. (1.2)
NOTE Dampers under this standard are required wherever the International Building Code, NFPA 90A, or the Authority Having Jurisdiction (AHJ) mandates a rated damper at a duct or air-transfer opening to preserve fire compartmentation or to control smoke migration. (1.3)
NOTE This standard covers the damper device and its directly associated sleeve, access door, actuator, and release mechanism. It does not cover the surrounding ductwork or the firestopping of the annular space, each of which is governed by its own standard and must be coordinated with the work here. (1.4)
NOTE The following are outside the scope of this standard. (1.5)
- General ductwork construction, materials, gauges, and sealing — see Hvac Ductwork.
- Volume control, balancing, backdraft, and motorized outdoor-air dampers used solely for airflow regulation — see Louvers And Dampers.
- Firestop sealants, intumescent collars, and through-penetration firestop assemblies at pipe and conduit penetrations — see Firestopping. The annular space around a fire damper sleeve in a rated assembly is firestopped under that standard.
- Engineered smoke-control pressurization systems, stairwell pressurization fans, and dedicated smoke-exhaust fans — see Smoke Control Systems. A smoke damper that is a component of an engineered smoke-control system is coordinated with that standard for system-level design, but the damper device itself is specified here.
- Radiation dampers used in rated assemblies for recessed light fixtures and similar penetrations.
- HVAC equipment such as air-handling units, variable-air-volume boxes, and fans.
2 Referenced Standards
2.1 Equipment, materials, listing, installation, and testing shall comply with the latest adopted edition of each of the following unless a specific edition is cited.
2.2 Where referenced standards conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.
NOTE Where the AHJ has adopted an edition of a code or standard that differs from the edition cited here, the AHJ-adopted edition shall govern. (2.3)
| Standard |
Title |
| UL 555 (Ed. 8, 2026) |
Fire Dampers |
| UL 555S |
Smoke Dampers |
| UL 555C |
Ceiling Dampers |
| NFPA 90A (2021) |
Installation of Air-Conditioning and Ventilating Systems |
| NFPA 80 (2022) |
Fire Doors and Other Opening Protectives |
| NFPA 105 (2021) |
Smoke Door Assemblies and Other Opening Protectives |
| NFPA 92 (2021) |
Smoke Control Systems |
| IBC (2024), Section 717 |
Ducts and Air Transfer Openings |
| SMACNA |
Fire, Smoke, and Radiation Damper Installation Guide for HVAC Systems |
| ASTM A653 |
Steel Sheet, Zinc-Coated (Galvanized) by the Hot-Dip Process |
| AMCA 500-D |
Laboratory Methods of Testing Dampers for Rating |
3 Submittals
3.1 The Contractor shall submit the following action submittals for review before fabrication or ordering:
- Product data for each damper type, including UL listing, fire rating, leakage class, and rated velocity and pressure.
- UL listing cards or classification marks for each damper assembly, sleeve, and actuator combination as installed.
- Shop drawings showing damper type, size, blade configuration, sleeve material and gauge, mounting orientation, and access-door location at each penetration.
- Actuator data sheets stating voltage, spring-return action, torque, and supervisory provisions.
- A damper schedule listing every damper by mark, location, assembly rating, type, leakage class, and required UL listing.
- Manufacturer installation instructions and the applicable UL-listed installation details for each assembly.
☑ Product data (each damper type)
☑ UL listing cards / classification marks
☑ Shop drawings with penetration details
☐ Actuator data sheets
☑ Damper schedule (by mark and location)
☑ Manufacturer installation instructions / UL details
3.2 The Contractor shall submit the following closeout submittals before final acceptance:
- Acceptance-test reports for the initial drop test and leakage verification of every installed damper.
- An as-built damper location schedule keyed to the construction documents and suitable for the building's periodic inspection program.
- Operation and maintenance data, including reset procedures and recommended inspection intervals.
- Manufacturer warranty documentation.
☑ Acceptance-test reports
☑ As-built damper location schedule
☑ Operation and maintenance data
☑ Warranty documentation
3.3 The Contractor shall submit the following informational submittals:
- Field quality-control test reports.
- Coordination documentation confirming actuator control voltage with the fire-alarm and building-automation control sections of the Contract Documents.
☑ Field quality-control test reports
☑ Actuator control-interface coordination record
4 Quality Assurance
4.1 Every fire, smoke, and combination damper shall be a complete factory-assembled unit listed and labeled by a nationally recognized testing laboratory under UL 555 or UL 555S as applicable.
4.2 Each damper assembly shall bear a permanent label identifying the testing laboratory, the listing standard, the fire rating, and, for smoke dampers, the leakage class.
4.3 Dampers shall not be modified, cut, or field-altered in any way that voids the UL listing.
4.4 The damper, sleeve, mounting angles, and actuator shall be assembled only in a configuration covered by the manufacturer's UL-listed installation instructions for the installed orientation.
4.5 Combination fire/smoke dampers shall be furnished by a single manufacturer as a listed assembly, including the actuator and release device, so that no field combination of components falls outside the listing.
4.6 The installing contractor shall be experienced in the installation of UL-listed life-safety dampers and shall install each unit strictly in accordance with the listed installation instructions.
5 Damper Type and Application
NOTE Combination fire/smoke dampers (1.5-hour, Class I leakage, dynamic) are the default device for general commercial construction. Because most new HVAC systems keep fans running during alarm or transfer air through smoke barriers, a single device that provides both fire closure and low-leakage smoke control is simpler to coordinate and inspect than separate fire and smoke dampers. Select a different type only where the application genuinely calls for it. (5.1)
5.2 A fire-only damper may be used where the penetrated assembly is fire-rated but is not a smoke barrier or smoke partition and no smoke-control function is required.
5.3 A smoke-only damper may be used where the penetrated assembly is a smoke barrier or smoke partition that is not separately fire-rated for duct penetration.
5.4 A combination fire/smoke damper shall be used where the penetration is through an assembly that is both fire-rated and a smoke barrier, or where the design otherwise requires both functions at one opening.
5.5 A corridor damper, listed specifically for corridor-ceiling and corridor-wall applications, shall be used where the IBC corridor exception applies; a standard combination damper shall not be substituted for a corridor-listed assembly.
● Combination fire/smoke damper
○ Fire damper (fire-only)
○ Smoke damper (smoke-only)
○ Corridor damper
5.6 Fire dampers shall be required where ducts and air-transfer openings penetrate fire barriers, fire partitions, fire walls, and fire-resistance-rated horizontal assemblies, per IBC Section 717.3.2.
5.7 Smoke dampers shall be required where ducts and air-transfer openings penetrate smoke barriers and smoke partitions, per IBC Section 717.3.3.
NOTE The damper required at each penetration shall be coordinated with the rated assembly it serves; the assembly rating, not the duct, determines the damper requirement. (5.8)
6 Fire Rating
NOTE The fire rating of each damper shall be keyed to the fire-resistance rating of the penetrated assembly per IBC Table 717.3.2.1, not selected independently. Specifying a lower-rated damper than the assembly requires is a code violation; over-rating the damper wastes cost and may exceed available listed sizes. (6.1)
6.2 Dampers in assemblies with a fire-resistance rating of less than 3 hours shall carry a fire-protection rating of not less than 1.5 hours.
6.3 Dampers in assemblies with a fire-resistance rating of 3 hours or more shall carry a fire-protection rating of not less than 3 hours.
NOTE The 1.5-hour rating is the correct default for the large majority of commercial assemblies, which are rated 1 to 2 hours. The 3-hour damper is reserved for 3-hour fire walls and floors and is both less common and more limited in available listed sizes. (6.4)
● 1.5-hour (assemblies rated less than 3 hours)
○ 3-hour (assemblies rated 3 hours or more)
7 System Designation: Static vs. Dynamic
NOTE A static-rated damper is tested to close under no-flow conditions; it relies on the supply or return fan shutting down on alarm so that the blade falls or drives closed against still air. A dynamic-rated damper is tested to close against a defined airflow and pressure and is required wherever the fan remains running during the fire event. (7.1)
7.2 Where the HVAC fan serving the penetration shuts down on alarm, a static-rated damper may be used.
7.3 Where the HVAC fan continues to operate during an alarm, including systems that maintain airflow for smoke control or pressurization, a dynamic-rated damper shall be used.
NOTE Specifying a static-rated damper in a dynamic (fan-on) system is a recurring and dangerous error. A static damper is not tested to overcome airflow and may stall partly open or fail to seal, defeating the rating at exactly the moment it is needed. Confirm the fan-shutdown sequence before selecting a static device. (7.4)
NOTE The dynamic rating, where required, shall be not less than the maximum system airflow velocity and static pressure at the damper at the time of actuation. (7.5)
● Dynamic (fan remains running on alarm)
○ Static (fan shuts down on alarm)
8 Blade Construction
NOTE Curtain-type (single interlocking-blade) dampers are economical and common for fire-only service, where the folded blade stack springs across the opening on release. Multi-blade dampers, with parallel or opposed airfoil or triple-vee-groove blades, are required for nearly all smoke and combination dampers because the multi-blade frame is what achieves a low-leakage seal and accepts a powered actuator. (8.1)
8.2 Curtain-type blade construction may be used for static or dynamic fire-only dampers within the listed size limits.
8.3 Multi-blade construction shall be used for all smoke dampers and all combination fire/smoke dampers.
8.4 Triple-vee-groove blades may be used in systems with duct velocity up to 2,000 fpm.
8.5 Airfoil blades shall be used in systems with duct velocity above 2,000 fpm and up to the listed maximum.
NOTE Specifying triple-vee-groove blades for a high-velocity duct produces a non-listed installation; the blade style must match the velocity range of the UL listing. (8.6)
○ Curtain-type (interlocking blade)
● Multi-blade, triple-vee-groove
○ Multi-blade, airfoil
NOTE Velocity and pressure ratings shall be verified against the duct system's design conditions; the listed rating of the damper shall equal or exceed the actual airflow velocity and static pressure at the damper. (9.1)
9.2 Curtain-type static dampers shall be applied within their listed velocity, typically up to 2,000 fpm.
9.3 Multi-blade dynamic dampers shall be applied within their listed velocity, typically up to 4,000 fpm with airfoil blades.
NOTE The damper's listed pressure class shall equal or exceed the duct system design pressure; most listed assemblies are rated to 4 in. w.g., and the 6 in. and 8 in. w.g. classes are reserved for special high-pressure applications. (9.4)
10004000
Default: 2000 fpm
2 in. w.g.
4 in. w.g.
6 in. w.g. (high-pressure applications)
8 in. w.g. (high-pressure applications)
10 Smoke Damper Leakage Class
NOTE Smoke dampers are rated by air leakage past the closed blade at a reference pressure, measured under UL 555S. A lower leakage class admits less smoke through the closed damper and is what allows a smoke barrier or an engineered smoke-control system to hold its design pressure differential. (10.1)
10.2 Class I leakage shall not exceed 4 cfm/ft² at 1 in. w.g.
10.3 Class II leakage shall not exceed 10 cfm/ft² at 1 in. w.g.
10.4 Class III leakage shall not exceed 40 cfm/ft² at 1 in. w.g.
10.5 Class I leakage shall be provided for smoke dampers in smoke barriers and for any smoke damper that is a component of an engineered smoke-control system.
NOTE Specifying Class II or Class III leakage where an NFPA 92 smoke-control design assumes Class I will cause the system to fail its performance verification; confirm the leakage class against the smoke-control design before selecting a lower class. (10.6)
● Class I (≤4 cfm/ft² at 1 in. w.g.)
○ Class II (≤10 cfm/ft² at 1 in. w.g.)
○ Class III (≤40 cfm/ft² at 1 in. w.g.)
11 Release and Actuation
NOTE A fire damper closes when heat melts a fusible link, releasing the spring-loaded blade. A smoke or combination damper closes when a powered actuator is de-energized or driven closed by an alarm signal; a combination damper carries both a fusible link for thermal closure and an actuator for alarm-initiated closure. (11.1)
11.2 Fusible links shall be rated for the maximum expected ambient temperature at the damper while reliably releasing at the lowest practical temperature above that ambient.
11.3 A 165°F (74°C) fusible link shall be the default for standard HVAC service.
11.4 A 212°F (100°C) fusible link shall be used in elevated-ambient locations such as near kitchen exhaust or unconditioned spaces.
11.5 A 286°F (141°C) fusible link shall be used only for special high-temperature applications where the lower-rated links would nuisance-release.
NOTE Specifying a higher-temperature fusible link than the ambient requires delays actuation and is inappropriate in normal office HVAC; 165°F is the correct default unless the ambient genuinely justifies a higher rating. (11.6)
● 165°F (74°C) — standard HVAC
○ 212°F (100°C) — elevated ambient
○ 286°F (141°C) — special high-temperature
11.7 Actuators for smoke and combination dampers shall be spring-return, fail-closed, so that loss of power or signal drives the damper to the safe (closed) position.
NOTE Non-spring-return actuators may be used only where supervised standby power holds the damper open and the failure mode is engineered acceptably. (11.8)
11.9 Actuator control voltage shall be confirmed against the fire-alarm and building-automation control sections of the Contract Documents before ordering; a mismatch between damper actuator voltage and panel output is a common and avoidable RFI.
11.10 A 24 VAC/VDC spring-return actuator shall be the default for systems integrated with a building-automation or fire-alarm panel.
11.11 A 120 VAC actuator may be used where the control interface is line-voltage.
● Spring-return, fail-closed
○ Non-spring-return with supervised standby power
11.12 The duty cycle of two-position spring-return actuators shall meet the UL 555S cycling requirement of not fewer than 20,000 open/close cycles.
11.13 Modulating actuators, where used, shall meet the UL 555S cycling requirement of not fewer than 250,000 cycles.
12 Smoke Detection and Control Interface
NOTE A smoke damper closes on a signal derived from smoke detection. The detector may be a duct-mounted unit wired directly to the actuator for a local response, or the closure command may originate at the fire-alarm panel or building-automation system for coordinated, building-wide control. The control architecture is a design decision that must be coordinated with the fire-alarm and BAS scope. (12.1)
12.2 Each smoke and combination damper shall close upon receipt of an alarm signal from the building fire-alarm system or its associated smoke detection.
12.3 The control interface, detector location, and wiring of each smoke and combination damper shall be coordinated with the fire-alarm and building-automation work and shown on the construction documents.
○ Duct-mounted detector wired directly to actuator
● Fire-alarm panel / BAS-commanded closure
13 Sleeve and Mounting
NOTE The sleeve carries the damper through the rated assembly and transfers the closing reaction into the structure. It must be continuous through the wall or floor, of the gauge and length covered by the UL listing, and detailed so the annular space can be firestopped. A sleeve that stops short of the assembly face or is the wrong gauge takes the installation outside its listing. (13.1)
13.2 The damper sleeve shall be continuous through the full thickness of the rated assembly.
13.3 Sleeves shall be galvanized steel conforming to ASTM A653 for standard interior applications.
13.4 Sleeves shall be stainless steel in corrosive or wet environments where galvanized steel would not be durable.
13.5 Sleeve gauge shall be not less than 16 ga for standard curtain-type and smaller multi-blade assemblies.
13.6 Sleeve gauge shall be not less than 14 ga for larger or heavier assemblies as required by the manufacturer's listing.
13.7 The annular space between the sleeve and the rated assembly shall be firestopped in accordance with the UL-listed assembly and with Firestopping. ● Galvanized steel (ASTM A653)
○ Stainless steel
NOTE Damper location, mounting orientation, and the routing of duct through each rated penetration shall be coordinated with the structural and architectural drawings.
damper penetration locations (13.8) 14 Duct Connections and Breakaway Joints
NOTE The duct must not restrain the damper blade as it closes. SMACNA and the UL listing require a breakaway (slip) connection between the duct and the damper sleeve so that, if the duct is distorted by fire, the connection releases and lets the damper close freely. Omitting the breakaway detail from the construction documents reliably generates field RFIs. (14.1)
14.2 A breakaway duct connection shall be provided at each damper sleeve in accordance with the manufacturer's UL-listed installation instructions and the SMACNA Fire, Smoke, and Radiation Damper Installation Guide.
14.3 Breakaway connections shall not be rigidly welded, screwed, or otherwise fixed in a manner that would prevent the duct from releasing from the sleeve.
NOTE Where the system design pressure or velocity exceeds the limits of a breakaway connection, a rigid connection listed for that condition shall be used as permitted by the damper listing. (14.4)
15 Access Doors
NOTE NFPA 80 and NFPA 105 require every damper to be reachable for inspection and for manual reset after a test or actuation. An access door must be provided at each damper, sized large enough to reset the device, and located where finish trades and concealed construction will not block it. Access doors that are omitted or buried above hard ceilings are the single most common reason a damper cannot be tested later. (15.1)
15.2 An access door shall be provided in the duct or sleeve at each fire, smoke, and combination damper.
15.3 Access doors shall be not smaller than 12 in. × 12 in.; 18 in. × 18 in. shall be provided where space permits to ease reset and inspection.
15.4 Access door locations shall be shown on the construction documents and coordinated with ceiling, wall, and finish work before close-in. damper access door locations 15.5 Access doors shall be labeled to identify the life-safety damper behind them.
● 12 in. × 12 in. (minimum)
○ 18 in. × 18 in. (preferred where space permits)
16 Round and Oval Duct Applications
NOTE A combination damper listed for rectangular duct is not interchangeable with one listed for round or oval duct. Where the duct system includes round or oval runs through rated assemblies, round-listed assemblies shall be separately specified rather than forcing a rectangular damper into a transition. (16.1)
16.2 Round or oval duct penetrations of rated assemblies shall be protected by dampers UL-listed for round or oval duct service in the installed orientation.
● Rectangular
○ Round
○ Oval
17 Sizing Limits
NOTE Every damper is listed to a maximum single-section size that depends on type, orientation, and static-versus-dynamic rating. Where an opening exceeds the listed single-section size, multiple sections shall be assembled into a mullion frame only as covered by the manufacturer's UL listing. (17.1)
17.2 Single-section curtain-type fire dampers shall not exceed the UL-listed maximum for the installed orientation; common limits are 60 in. × 60 in. vertical static, 40 in. × 40 in. horizontal static, and 36 in. × 36 in. vertical dynamic.
17.3 Multi-blade damper section sizes shall not exceed the maximum size of the individual UL-listed product.
NOTE Multi-section (mulled) assemblies shall be furnished and installed only in the frame configuration covered by the manufacturer's listing. (17.4)
18 Testing
18.1 Before the building is occupied, every installed fire, smoke, and combination damper shall be tested to confirm it operates and closes fully, in accordance with NFPA 90A acceptance requirements.
18.2 Each fire damper shall be drop-tested by releasing the fusible link to confirm the blade closes fully and latches; the link shall then be reinstalled and the damper reset to its normal position.
18.3 Each smoke and combination damper shall be cycled from the control interface to confirm the actuator drives the damper fully closed on signal and reopens on restoration.
NOTE Smoke dampers serving engineered smoke-control systems shall be verified to achieve their specified leakage class as part of smoke-control system acceptance under
Smoke Control Systems.
(18.4) 18.5 Any damper that fails to close fully, seal, or reset shall be corrected and retested before acceptance.
18.6 Acceptance-test results shall be recorded for each damper and included in the closeout submittals.
NOTE Following installation, the building's periodic inspection and testing program shall follow the schedule of NFPA 80 (§19.4) for fire dampers and NFPA 105 (§6.5) for smoke dampers: an initial test one year after installation, then at intervals of four years for standard occupancies and six years for hospitals. (18.7)
● 4 years (standard occupancy)
○ 6 years (hospitals)
19 Installation
19.1 Each damper shall be installed in strict accordance with its UL-listed installation instructions for the installed orientation; the listing is void if the field installation departs from the listed details.
19.2 Mounting angles or retaining angles shall be installed on both faces of the assembly as required by the listing, lapping the opening to retain the sleeve and damper.
19.3 The damper blade stack and actuator shall be installed so the blade is free to travel its full range without obstruction by duct, insulation, or structure.
19.4 Dampers shall be installed square and plumb within the listed tolerance so the blade seats fully; racking the sleeve to fit a misaligned opening is prohibited.
19.5 Insulation, lining, and duct accessories shall be kept clear of the blade path and the actuator linkage.
19.6 The contractor shall coordinate damper installation with the firestopping of the annular space so that firestop materials do not foul the sleeve or block the access door, per Firestopping. 19.7 A permanent identification tag shall be affixed at each damper recording its mark and type for the building's inspection program.
20 Damper Schedule and As-Builts
NOTE A complete, tabulated schedule of every damper location is essential to the building's life-safety program. Without it, a future NFPA 80/105 inspection cannot find every device — particularly dampers concealed above hard ceilings or in shafts — and untested dampers silently defeat the compartmentation they were installed to provide. (20.1)
20.2 A damper schedule listing every damper by mark, location, assembly rating, type, leakage class, and UL listing shall be prepared and maintained through construction.
20.3 An as-built damper location schedule, updated to reflect final installed locations, shall be delivered at closeout for use by the building's periodic inspection program.
21 Delivery, Storage, and Handling
21.1 Dampers shall be delivered with their UL labels intact and their factory blocking or shipping ties in place to protect the blade stack and actuator.
21.2 Dampers shall be stored indoors, protected from moisture, dust, and physical damage, and kept on supports off the floor.
21.3 Actuators and fusible links shall be protected from impact and from temperatures outside the manufacturer's storage range.
21.4 Shipping blocking shall be removed and the damper verified to operate freely before final connection and testing.
22 Warranty
22.1 The manufacturer shall warrant each damper assembly, including the actuator and release mechanism, against defects in materials and workmanship for not less than the period specified below from the date of Substantial Completion.
○ 1 year
● 2 years
○ 5 years
22.2 The warranty shall cover repair or replacement of defective dampers, actuators, and release devices at no cost to the Owner during the warranty period.
23 Spare Parts
23.1 The Contractor shall furnish spare fusible links of each temperature rating used on the project so that links consumed during the initial drop test or future testing can be replaced without delay.
23.2 The Contractor shall furnish spare actuators of each type and voltage used on the project for the Owner's maintenance stock.
☑ Spare fusible links (each rating used)
☑ Spare actuators (each type/voltage used)
☐ Manufacturer-recommended maintenance kit