SF-86-12-2 -- Fire Protection Criteria for Air Ducts ✓ Most Recent

The American Iron and Steel Institute (AISI) commissioned Underwriters Laboratories, Inc. (UL), to perform a fire test on undampered HVAC ducts penetrating a one-hour rated wall . The test was conducted on January 3, 1985. The purpose of this test was to complement the already overwhelming evidence that fire dampers in steel ducts are not needed to maintain the fire integrity of one-hour rated walls when penetrated by steel HVAC ducts.

The ASTM E119 (NFPA 251, UL 263) Standard Fire Test for Walls or Partitions was used as the basic test setup to evaluate the duct as a fire-stopping material . The performance of the test assembly, and in particular the duct penetration, was evaluated using realistic failure criteria for the spread of fire based on those for fire doors and fire dampers in ASTM E152, Standard Methods of Fire Tests of Door Assemblies and UL 555, Standard for Fire Dampers and Ceiling Dampers, respectively. These duct assemblies were tested, all in the positive pressure area near the top of the wall in the test furnace (positive pressure as compared to the testing laboratory atmosphere). None of the duct assemblies contained fire dampers. The three duct assemblies were: an uninsulated steel duct, a steel duct wrapped with insulation, and a Class 1 rigid fiberglass duct. In order to simulate continuous air ducts through a fire compartment, both ends of the duct were closed and 6-inch square open drops were located near the ends of the duct inside and outside the furnace.

In addition to testing with duct structural failure criteria in mind, temperature measurements on and near, the ducts on the unexposed side were taken to evaluate the potential for ignition of combustible material adjacent to the ducts.

Units: I-P