Basic Life-Safety Damper Types
Knowing the Differences Makes All the Difference in Application
By the Air Movement and Control Association (AMCA) International Inc. Fire and Smoke Damper Subcommittee
Among the many aspects of fire and smoke protection for which fire protection engineers are responsible is the placement and use of life-safety dampers. This article details the fundamental features of each of four basic types of life-safety dampers:
- Ceiling radiation
- Combination fire/smoke, including corridor dampers
Ceiling radiation dampers generally are used in apartment buildings, nursing homes, retirement facilities and the like, where each unit has its own HVAC system. Fire, smoke and combination fire/smoke dampers are used in primarily hospitals, hotels, high-rises and other facilities where a single air-handling unit (AHU) supplies multiple occupancies and/or floors.
In all cases, life-safety dampers must be installed per manufacturer instructions to be UL- and building code-compliant. Instructions cover sleeve-to-ductwork breakaway connections, distance limits, retaining angles (for blocking gaps between damper sleeves and openings, and securing dampers to barriers), and any firestopping requirements.
Ceiling Radiation Dampers
A ceiling radiation damper restricts the transfer of heat from a fire below it into a fire-rated ceiling assembly, such as a drop or gypsum ceiling. It is not tested for fire resistance or smoke leakage, although it restricts both to some degree simply by blocking the opening created by a duct or a drop-in grille. Normally, it is spring-loaded with a fusible link that melts at 165°F (74°C) or 212°F (100°C) and is mounted directly above a ceiling diffuser or grille. It is not individually hourly rated, but, rather, rated as part of a ceiling assembly. It is certified to UL 555C, Standard for Ceiling Dampers.1
Two examples of ceiling radiation dampers are shown in Figure 1.
Figure 1. Ceiling radiation dampers. Photo courtesy of United Enertech.
Chapter 7 of the 2018 International Building Code (IBC)2
requires fire dampers to be installed where duct or transfer openings penetrate firewalls, fire barriers, fire partitions, horizontal assemblies or shaft enclosures. Their primary function is to prevent the passage of flame from one side of a fire-resistance-rated assembly to the other. They are certified to UL 555, Standard for Fire Dampers.3
There are two basic types of fire dampers:
- Curtain (Figure 2)
- Bladed (single or multi-) (Figure 3)
Static curtain dampers are rated only for applications in which fans shut down during an event. Dynamic curtain dampers are designed and tested to close under heated airflow and, thus, can operate fully with fans running. Roughly 90 percent of curtain fire dampers are activated by a 165°F (74°C) fusible link. The maximum heat-response device setting is 212°F (100°C) for static dampers and 350°F (177°C) for dynamic dampers. Most motorized bladed fire dampers are available with bimetal heat-responsive control.
Figure 2. Curtain fire damper with fusible link and factory-integral sleeve. Photo courtesy of Ruskin.
Figure 3. Sleeved two-section multiblade fire damper with heat-responsive devices. Photo courtesy of Greenheck.
Fire dampers approved for dynamic systems also are approved for static systems. Fire dampers approved for static systems, however, are not approved for dynamic systems, as they may not close under airflow.
Figure 4 shows a typical fire-damper installation.
Figure 4. Typical fire-damper installation. Image courtesy of Ruskin.
Certified under UL 555S, Standard for Smoke Dampers,4
smoke dampers (Figures 5 and 6) are used to provide isolation between smoke zones, for smoke extraction or to pressurize an area. They are controlled by a local smoke detector or an area smoke-detection system. Because there is no mechanical method for detecting smoke, all smoke dampers are motorized, requiring an electronic signal to open or close.
Chapter 7 of the IBC requires smoke dampers to restrict smoke movement where ducts and air-transfer openings penetrate smoke barriers or partitions, while Chapter 9 of the IBC requires smoke dampers be capable of being opened or closed from a remote command station.
IBC Chapter 7 applications often are referred to as part of “passive smoke control” or “containment,” because they maintain compartmentation. IBC Chapter 9 applications are “active,” because they can be controlled remotely from a fire alarm/smoke control panel. They are part of an engineered smoke-control system.
Figure 5. Smoke damper with an axle shaft-mounted actuator. Photo courtesy of TAMCO.
Figure 6. Smoke damper with a jackshaft-mounted actuator. Photo courtesy of Nailor.
NFPA 105, Standard for Smoke Door Assemblies and Other Opening Protectives,5 and NFPA 90A, Standard for the Installation of Air-Conditioning and Ventilating Systems,6 state that smoke dampers are to be located no more than 24 in. from the smoke-barrier opening they are protecting and installed on both the supply and return sides of ducts entering a smoke compartment. A UL-approved sealant is required to seal a smoke damper to a duct/sleeve. Manufacturer instructions provide approved installation details.
Smoke dampers (as well as combination fire/smoke dampers and corridor dampers) are leakage-rated. Table 1 shows the maximum leakage value at a specific pressure for each UL leakage classification. The IBC requires at least a Class II leakage rating.
Table 1. Leakage classes (maximum cubic feet per minute per square foot).
Combination Fire/Smoke Dampers
Evaluated and tested to both UL 555 and UL 555S, combination fire/smoke dampers (Figure 7) meet the aforementioned requirements for dynamic fire and smoke dampers. They are used where HVAC assemblies penetrate openings and are required to have both a fire damper and a smoke damper. These dampers close upon the detection of heat (via duct temperature) or smoke (via a smoke detector or relay from an area smoke detection system). They protect the opening inside a duct and outside at the barrier.
Figure 7. Combination fire/smoke damper with electric heat-response devices. Photo courtesy of Pottorff.
The heat-response device of most combination fire/smoke dampers is an electrical thermal switch instead of a fusible link. Using an actuator’s spring allows for a more-controlled closure. This avoids dampers slamming closed too fast, which can cause pressure spikes, which, in turn, can cause ducts to collapse or seams to split.
Corridor dampers are combination fire/smoke dampers tested to close at a lower airflow velocity. They are required in the ceilings of corridors used for egress.
Life-safety dampers should always be installed per the manufacturer’s instructions. One manufacturer’s installation instructions never should be used in place of another’s because of the uniqueness of individual damper assemblies and how they are tested. Instructions must be made available to the authority having jurisdiction during installation review. UL certification requires that a set of installation instructions be included in each shipping container of life-safety dampers.With any building system, inspection and maintenance are essential to proper operation. While ceiling radiation dampers do not require periodic inspection, fire, smoke and combination fire/smoke dampers do, which means access doors. NFPA 105 and NFPA 80, Standard for Fire Doors and Other Opening Protectives,7
require dampers to be tested during commissioning, one year after installation, and every four years thereafter (except for hospitals, for which the frequency is every six years). The inspections must be documented, with the location of the damper, date of the inspection, name of the inspector and inspection agency, and any deficiencies that were discovered noted. These requirements are found in Section 701.6 and Section 706.1 of the International Fire Code.8
Increasingly, with modern technology, fusible-link life-safety dampers are giving way to motorized life-safety dampers with factory-supplied remote blade-position indication. This has had the effect of helping to make life-safety dampers addressable — that is, able to talk to building management systems (BMSs). Connection to a BMS allows these dampers to assist in balancing the AHU for normal building operation, and ensures that dampers close to resist the passage of flame and/or smoke during a fire event.
Addressable motorized dampers with factory-supplied remote blade-position indication also can be connected to a fire alarm panel. This enables the panel to direct smoke-evacuation fans and dampers to open or close to prevent smoke migration, or dampers to open for smoke purge.
With addressability, dampers connected to a BMS or a fire alarm panel can be monitored 24/7. If a damper closes or opens without a command from the system, a notice can be acknowledged and repairs performed promptly. This advantage means that dampers can be tested as required by NFPA 80 and NFPA 105 without interruption of day-to-day facility operation.
Typically, for testing, someone has to climb up into a ceiling cavity and manually cycle dampers. Conversely, through a fire alarm or BMS, dampers can be commanded to close and reopen and a report of which dampers were cycled and any that were not can be generated automatically. This remote testing of dampers can save facility owners thousands of dollars every year that testing is required.
There are four general types of life-safety dampers:
- Ceiling radiation — used to prevent heat from a fire below from penetrating a ceiling membrane.
- Fire — used to prevent the transfer of flame across firewalls, fire barriers and fire partitions.
- Smoke — used to restrict the passage of smoke in IBC Chapter 7 applications and to restrict the passage of smoke, to direct smoke or for pressurization in IBC Chapter 9 applications.
- Combination fire/smoke (including corridor dampers) — used to prevent the passage of flame, restrict the passage of smoke or direct smoke, or for pressurization.
Life-safety dampers are a form of passive fire protection. A life-safety system should include both passive and active forms of fire protection, including notification and suppression. Passive and active elements working together allows a safe means of egress and a safer environment for firefighters.
Damper manufacturers provide instructions detailing UL-certified installation methods.
Periodic maintenance of dampers is the building owner’s responsibility. NFPA 80 and NFPA 105 provide details.
1UL. (2014). Standard for Ceiling Dampers. UL 555C. Northbrook, IL: UL.
2ICC. (2018). 2018 International Building Code. Country Club Hills, IL: International Code Council.
3UL. (2006). Standard for Fire Dampers. UL 555. Northbrook, IL: UL.
4UL. (2014). Standard for Smoke Dampers. UL 555S. Northbrook, IL: UL.
5NFPA. (2019). Standard for Smoke Door Assemblies and Other Opening Protectives. NFPA 105. Quincy, MA: National Fire Protection Association.
6NFPA. (2018). Standard for the Installation of Air-Conditioning and Ventilating Systems. NFPA 90A. Quincy, MA: National Fire Protection Association.
7NFPA. (2019). Standard for Fire Doors and Other Opening Protectives. NFPA 80. Quincy, MA: National Fire Protection Association.
8ICC. (2018). International Fire Code. Country Club Hills, IL: International Code Council.