Dampers are devices to prevent transmission of flame or smoke or both where air ducts penetrate through fire barriers. A fire barrier is a fire-resistant fire-rated vertical or horizontal assembly of materials designed to restrict the spread of fire.
They can also be employed in air transfer openings in walls and partitions. Building codes specify where fire or smoke or combination dampers are required.
Fire and/or smoke resisting dampers represent a major method used worldwide to prevent passage of fire & smoke from one building compartment to another through duct and air transfer openings i.e. Heating, Ventilation and Air Conditioning (HVAC) systems.
Functionally, dampers are segregated into five unique categories:
- Fire Dampers
- Smoke Dampers
- Combination Dampers
- Corridor Dampers
- Ceiling 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 no or negligible 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 incident, and are expected to be able to operate (close) against the air velocity and pressure produced by the system fan.
Both fire dampers for use in dynamic and static systems certified by UL carry an hourly fire resistance rating, usually 1-1/2 or 3 hours. Fire dampers for use in dynamic systems are also provided with an airflow rating which indicates the maximum velocity and static pressure that the damper is designed for. 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 Standard for Fire Dampers, UL 555.
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, 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 though smoke barriers, or at other locations within an engineered smoke control system. A smoke barrier is a continuous membrane, either vertical or horizontal, such as a wall, floor, or ceiling assembly, which is 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 the Standard for Smoke Dampers, UL 555S.
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 Standard for Fire Dampers, UL 555 and the Standard for Smoke Dampers, UL 555S.
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 & 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 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.
Ceiling dampers are evaluated by UL in one of two ways as explained below.
Ceiling Dampers for Use in Lieu of Hinged Door Type Dampers
Ceiling dampers can been investigated for use in lieu of hinged door type dampers in floor-ceiling or roof-ceiling designs which contain air ducts and specify the use of hinged door type dampers over each duct outlet. The basic Standard used for a ceiling damper evaluated in this fashion is The Standard for Ceiling Dampers, UL 555C. It is important to note that ceiling dampers covered by this scheme are only intended for use in those UL fire resistive designs that indicate the use of a hinged door type damper in the design. This information is located in UL's Fire Resistance Directory in the text and drawings of the specific designs. The UL Classification of the ceiling damper does not cover the product for general installation in any floor or ceiling design.
Ceiling Dampers for Use in Specific Fire Resistive Designs
Alternatively, some ceiling dampers have been investigated for use only in one or more, specific UL fire resistive floor-ceiling or roof-ceiling designs. Dampers covered by this method of evaluation are generally tested along with the specific design construction in accordance with the Standard for Building Construction Materials, ANSI/UL 263. Information describing the installation of ceiling dampers covered under this scheme, including a reference to the specific ceiling damper model, is included in the text and drawings for the specific designs, in UL's Fire Resistance Directory. The Classification text for the ceiling damper will also make reference to the specific floor-ceiling or roof-ceiling designs for which it is intended to be installed. An example of this scenario can be found in UL Fire Resistive Designs L501, L521, and L550.