UL 555 - Standard for Fire Dampers - Sections 1-10
The Fifth Edition of the U.L. Standard for Fire Dampers came into effect on May 31, 1995 replacing the fourth edition, which was originally released in January 1990. The requirements of the standard involve fire damper assemblies rated at 1/2, 1 1/2, and 3 hour endurance. The fire dampers covered are intended for HVAC ducts which pass through fire rated walls, partitions, or floor assemblies. All such penetrations through these rated assemblies are taken to be in accordance with the applicable codes such as the Standard for Installation of Air-conditioning and Ventilation Systems NFPA 90A, the BOCA National Mechanical Code, the Standard Mechanical Code, and the Uniform Mechanical Code.
The two types of fire dampers tested are for use with systems that are either static, a system that shuts down automatically in the event of a fire, or dynamic, a system that remains operational during a fire. Fire dampers intended for use with dynamic systems are tested for closure under maximum specified air flow.
Fire dampers are intended to close automatically through detection of heat by a fusible link. Some damper assemblies allow for reopening of the dampers in order to facilitate smoke removal. The fusible links employed by any fire damper assembly are to have activation temperatures of no less than 160 F and no more than 286 F.
Each damper design is tested through a representative range of sizes. For the endurance and hose stream tests, the largest size for a given design is evaluated. For operation and cycling tests, size criteria for testing is dependent upon both shape (rectangular vs. round) and actuation (spring vs. no spring).
The representative design samples are subjected to a Fire Endurance and Hose Stream Test. In this test, the assembly is subjected to a standard fire with known time-temperature characteristics. The fire is to be monitored by no less than 9 thermocouples symmetrically arranged about the test assembly. During the first two hours, temperature readings are to be taken at 5 minute intervals after which the intervals may increase to no more than 10 minutes. When compared to the standard curve, the actual time temperature data is to be accurate within 10% for tests of less than 1 hour, 7.5% for tests between 1 and 2 hours, and 5% for those longer than 2 hours.
For single damper assemblies, two samples of the design are installed, one with the upstream side facing the furnace and the other with the downstream side facing the furnace. With multiple assemblies, half are installed with the downstream side to the furnace and half with the upstream side to the furnace. If an assembly contains an odd number of dampers, the extra assembly is installed on the upstream side.
The test assembly is subjected to the fire for the time it is to be rated, or until the specimen fails. The damper assembly is then subjected to a hose stream from a 2 1/2" hose at a predetermined standard pressure.
Test performance for the Fire Endurance and Hose Stream Test is evaluated according to damper closing time, fire resistance, and warpage. All dampers are to close and latch automatically, where a latch mechanism applies, within the first 60 seconds of exposure to the fire. During fire exposure there is to be no flaming of damper components on the unexposed side. Any warping of the damper to due to the furnace or hose stream should not cause any warpage that would create visible openings through the damper assembly
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