Fire- and smoke-protective curtains
A fire- and smoke-protective curtain assembly comprises a flexible heat-resistant fabric impregnated with a coating to limit air infiltration and concealed in a head box, which is installed and located near or within the ceiling. On receiving signal from a fire-detection device, they automatically deploy. The curtain unfurls from the head box, thereby separating one area from another. While not 100 percent fail-safe, they also deploy via gravity on loss of power. The bottom of the curtain can be weighted to assist with deployment and limit deflection caused by air movement. The curtains are unlikely to land on someone because they are lightweight and descend at only 0.15 m (0.49 ft) per second.
Fire and smoke curtain assemblies have many recognized applications in office buildings, retail stores, universities, shopping centers, and museums in Europe, where they have been used for more than three decades. In the United States, the products began to be marketed to the commercial building industry in the mid-1990s. Currently, fire- and smoke-protective curtains provide nonstructural separation only, and are not intended to be substituted for structural hourly rated partitions or opening protectives that have been tested for fire endurance and hose stream performance. Test standards and code allowances are being developed for these products to realize their full potential. The final authority for the approved use of fire curtains rests with the authorities having jurisdiction (AHJs).
Testing requirements
Various facilities, including UL, Intertek, Factory Mutual, and Southwest Research Institute, are qualified to test these products. Determining the suitability for a desired application of a fire- and smoke-protective curtain assembly depends on the depth of understanding by the designers and AHJs of the applicable codes and standards. The following tests are relevant for determining the appropriate uses of fire and smoke protection assemblies.
NFPA 80-2016, Standard for Fire Doors and Other Opening Protectives, regulates the installation and maintenance of assemblies and devices used to protect openings in walls, floors, and ceilings against the spread of fire and smoke within, into, or out of buildings. The 2016 edition includes a new definition for “Fire-protective Curtain Assemblies” and associated Chapter 21. Paragraph 21.1.2 requires the testing of fire-protective curtain assemblies in accordance with ANSI/UL 10D-2014, Standard for Fire Tests of Fire-protective Curtain Assemblies.
ANSI/UL 10D evaluates fire-protective curtain assemblies intended to provide supplemental, passive fire protection as part of an engineered fire protection system. This is a relatively new standard, adapted from ANSI/UL 10C-2016, Positive-pressure Fire Tests of Door Assemblies, to specifically address fire-protective curtain assemblies. These curtains have the ability to withstand exposure to a fire-endurance test conducted in accordance with the standard-time temperature curve of ANSI/UL 263-2011, Standard for Fire Tests of Building Construction and Materials, and ASTM E119-16a, Standard Test Method for Fire Tests of Building Construction and Materials, under positive pressure, without the development of through openings in the curtain, or flaming of the material on the unexposed side of the assembly, for the duration of the hourly rating. (The following was copied from the 2015 IBC Section 703.5.2, “Composite Materials.” Fabrics having a structural base of noncombustible material as determined in accordance with IBC Section 703.5.1 with a surfacing of not more than 3.18 mm [0.125 in.] thick and has a flame spread index not greater than 50 when tested in accordance with ASTM E84, Standard Test Methods for Tension Testing of Metallic Materials, or UL 723, Standard for Test for Surface Burning Characteristics of Building Materials, shall be acceptable as a noncombustible product.)
Two primary tests are used for evaluating fire-resistive building elements, components, and assemblies. Both test methods (ANSI/UL 263 is equivalent to ASTM E119), prescribe a standard fire exposure controlled by the test facility to meet specified temperatures during a specified time. On completion of the fire endurance test, the assembly is subjected to the impact, erosion, and cooling effects of a hose stream of water. These test standards require temperatures to be recorded on the assembly’s unexposed surface.
As fire- and smoke-protective curtain assemblies are thermally thin, they cannot meet the temperature limits established by the standards on the unexposed surface, even though they are subjected to the standard time-temperature curve included therein. It is also virtually impossible for the current generation of fire- and smoke-protective curtain assemblies to withstand effects of the hose stream test on completion of the fire endurance test.
Unlike ASTM E119, ANSI/UL 10D does not require the products to limit temperature on the unexposed surface. Additionally, the impact of the hose stream test after fire exposure is not required. Therefore, fire- and smoke-protective curtains are not suitable as fire walls, fire barriers, fire partitions, smoke barriers, shaft enclosures, or rated floors (horizontal assemblies) as defined by the model codes.
NFPA 105-2016, Smoke Door Assemblies and Other Opening Protectives, prescribes minimum requirements for smoke door assemblies intended to protect life and property from smoke. The 2016 edition includes a new definition for “Smoke Protective Curtain Assembly” and associated Chapter 8.
Smoke door assemblies are required to be leakage tested in accordance with ANSI/UL 1784-2015, Air Leakage Tests for Door Assemblies, and identified by an “S” label attached to the bottom bar of the curtain indicating a maximum air leakage rate of 0.9 m3/min/m2 (3 cf/min/sf) and the tested pressure differential of 25 Pa (0.1 in.), 50 Pa (0.2 in.), or 75 Pa (0.3 in.) of water. These requirements correlate with IBC Section 710.5.2.2, “Smoke Partitions.” NFPA 105 Paragraph A.8.1.1, “Smoke Protective Curtain Assemblies,” clarifies fire-protective curtain assemblies are not to be confused with fabric fire-safety curtain assemblies specifically intended for protection of proscenium openings.
ANSI/UL 1784 is the test standard used to determine air leakage through door assemblies and other opening protectives installed in wall openings where air leakage is intended to be controlled.
Fire- and smoke-protective curtain assemblies may also be tested in accordance with the requirements of UL 10B-2008, Standard for Fire Tests of Door Assemblies, and ANSI/UL 10C.
These two test standards require temperatures to be recorded on the unexposed surface of the assembly. On completion of the fire endurance test, the assembly is subjected to the impact, erosion, and cooling effects from a hose stream. As mentioned, fire- and smoke-protective curtain assemblies are thermally thin. Therefore, they cannot meet the temperature limits on the unexposed surface. (As a conductive material, uninsulated steel has similar limitations.) After being subjected to the fire test, most fire- and smoke-protective curtain assemblies are unable to hold up to the hose stream, but some niche products can. To obtain recognition under UL 10B or UL10C, these portions of the test are typically not included.
NFPA 252-2017, Standard Methods of Fire Tests of Door Assemblies, is essentially an equivalent to UL 10B and UL 10C. The test can be run with the neutral pressure level at 9953.6 Pa (40 in.) or less above the sill (UL 10C and UL 10D, and IBC Section 716.5.1, “Side-hinged or Pivoted Swinging Doors”) or at the top (UL 10B and IBC Section 716.5.2, “Other Types of Assemblies”).
