Dampers
Dampers are organized into five unique product types. Their functions vary depending on the damper category.
Fire dampers
Fire dampers are used to prevent transmission of flame where air ducts penetrate fire barriers. A fire barrier is a fire-resistant-rated vertical or horizontal assembly of materials designed to restrict the spread of fire in which openings are protected. They can also be employed in air transfer openings in walls and partitions. Building codes specify where fire dampers are required. Fire dampers are available in two types, static fire dampers and dynamic fire dampers.
Fire dampers for use in static systems, as their name implies, are used in duct systems or penetrations where there is negligible or no airflow when the damper closes. Fire dampers for use in dynamic systems are required at locations in which fan pressure will be on during a fire, and are expected to be able to operate (close) against the air velocity and pressure produced by the system fan.
Fire dampers for use in both dynamic and static systems certified by UL carry an hourly fire resistance rating, usually 90 minutes or 3 hours. Fire dampers for use in dynamic systems are also provided with an airflow rating that indicates the maximum velocity and static pressure that the damper is designed to sustain. Refer to the section in this guide entitled airflow ratings for a more detailed explanation of the limitations of the ratings.
The basic standard used to evaluate fire dampers is the UL 555, the Standard for Safety of Fire Dampers.
Smoke dampers
Smoke dampers are intended for installation in ducts and air transfer openings that are designed to resist the passage of air and smoke. The devices are installed to operate automatically and are controlled by a smoke detection system, and where required, capable of being positioned from a remote command station.
Smoke dampers may be required where ducts penetrate through smoke barriers or at other locations within an engineered smoke control system. A smoke barrier is a continuous membrane that is either vertical or horizontal such as a wall, floor or ceiling assembly. They are designed and constructed to restrict the movement of smoke. Smoke dampers can be used in HVAC systems where the fans are shut down in the event of fire and can also be used in smoke control systems designed to operate during a fire incident. Smoke dampers are designed to operate against air velocity and fan pressure.
Smoke dampers certified by UL carry a leakage class rating that indicates the level of air leakage measured through the damper under test conditions. Smoke dampers are also provided with an airflow rating which indicates the maximum velocity and static pressure for which the damper is designed. Refer to the section in this guide entitled airflow ratings for a more detailed explanation of the limitations of the ratings.
The basic standard used to evaluate smoke dampers is UL 555S, the Standard for Safety of Smoke Dampers.
Combination fire and smoke dampers
These dampers are used at locations that are designated as both fire barriers and smoke barriers to prevent the passage of both flame and smoke. Dampers that are marked as combination dampers comply with both the UL 555and UL 555S.
Corridor dampers
A corridor (sometimes referred to as exit corridor or tunnel corridor) is an enclosed exit access component that defines and provides a path of egress travel to an exit. Corridor dampers are combination fire and smoke dampers that have been evaluated for mounting only in specific corridor ceiling constructions. The specific corridor ceiling construction details are described in the installation instructions provided with the dampers.
Corridors are intended as a means of egress in the event of a fire emergency. The building codes define the use and location of corridors in building construction. The building codes should be consulted for construction specifications for corridor ceilings.
Ceiling dampers
Ceiling dampers are used to limit the passage of heat in fire resistive floor-ceiling or roof-ceiling assemblies where ducts or other penetrations are made only through the ceiling membrane of the fire resistive assembly. Fire resistive ceiling membranes are part of floor-ceiling or roof-ceiling assemblies that have been evaluated for their fire resistive capabilities when evaluated in accordance with the Standard for Building Construction Materials, ANSI/UL 263 (ASTM E119, NFPA 252, UBC 7-1). Fire rated designs evaluated by UL are published in UL's Fire Resistance Directory.
Since ceiling dampers are intended to function only as heat barriers, and the building codes have not defined the use of these products in so far as their use as smoke barriers, the UL certification does not include the use of these products to limit the migration of smoke.
Special notice regarding ceiling dampers: This is to advise that UL has not authorized the use of ceiling dampers in Design Number L528 as published in UL's fire resistance directory. This information is being provided in response to publications by other certification agencies that state that ceiling radiation dampers and insulated plenum boxes are acceptable for installation in partition types L-528.
For additional information regarding dampers, see the UL Marking Guide for Dampers for Fire Barrier and Smoke Applications and Ceiling Dampers. The guide was developed for use by contractors, code and inspection authorities, installers, users and system designers to aid in the understanding of the scope of UL certification of dampers. The guide is also intended to assist in determining the suitability of these products for use in specific applications.
