FM Approvals will release a new standard—Approval Standard 4883, Insulated Wall Curtains, in the fourth quarter of 2017—that will provide the first-ever fire performance criteria specifically for the evaluation and certification of insulated wall curtain systems. The new standard provides research-based requirements for flammability characterization, fire performance, smoke generation thresholds and optional surface burning.
Insulated wall curtain (IWC) systems are temporary or moveable semi-rigid panels or flexible curtains that are used to partition off interior spaces in warehouses or manufacturing facilities. These systems typically consist of an outer layer of industrial-grade, high-strength vinyl enclosing one or more layers of insulation. The insulation varies with the manufacturer, and may be polyester fiber, metalized polyethylene (PE) bubble wrap or insulations with various types of fire retardant materials.
IWC systems are usually installed vertically from cables, rods or brackets attached to ceiling structures. Some systems can be installed as freestanding structures. The flexible or semi-rigid panels are joined using Velcro® or other types of closure systems. Some systems can be retracted accordion-style in sliding channels.
These flexible partitioning and enclosure systems are used by many different industries to provide improved temperature control in refrigerated facilities or protect inventory or stock from temperature and humidity extremes. The use of IWC systems can help reduce energy consumption, protect products, reduce condensation and control noise.
New Standards Take Teamwork
Approval Standard 4883 (FM 4883) has been developed over the past two years using a multifunctional team approach involving FM Approvals, FM Global research, and FM Global engineering standards. The need for a fire performance standard covering insulated wall curtains was identified by FM Global field engineers who saw increased use of these systems, particularly among clients with large refrigerated warehouses.
“Going back five or six years, we began to see a growing use of insulated wall curtains by our clients,” explains John Harrington, staff vice president, senior engineering technical specialist for FM Global. “Because these systems are used to divide internal spaces, we were primarily concerned with flammability. Initially, we had no way to determine the good from the bad when it came to fire risk. We began conducting small-scale risk service testing using a benchtop parallel panel test to evaluate samples that measured six inches by 18 inches.”
According to Harrington, the small-scale testing raised concerns about the flammability of certain products, but was not conclusive enough to make firm recommendations. “In this case, we could not derive a lot of confidence from a benchtop test in how quickly a fire will spread or the how much smoke it will generate, compared with intermediate or large-scale testing,” Harrington notes. “We believed we needed to do more in-depth research and develop a pass/fail standard as opposed to trying to make judgments based only on small-scale tests.”
Research Shows the Way
FM Global senior research scientist Gaurav Agarwal led the effort to evaluate available IWC products in order to establish the performance requirements that would be the basis for FM 4883. Manufacturers of currently available IWC systems use a variety of fire resistance tests to evaluate the materials used in their products. While these tests—including ASTM E-84, NFPA-701 and FMVSS-302—provide important information about the comparative surface burning performance of IWC materials, they are not sufficient to fully characterize the fire hazards of IWCs in actual installations.
“For instance, the horizontal configuration of the ASTM E-84 test is not representative of the vertical installation of IWC panels,” Agarwal explains. “In addition, the test-scale and fire source used in NFPA-701 are not representative of the scales of IWC installations in industrial warehouses.”
The research team chose five different IWC systems for fire testing from various manufacturers. “We sought out products that provided a good cross section of what was available on the market,” Agarwal notes. “We wanted different types of coverings, insulations and fastening systems. Although these systems are similar in design, they do use different materials or include certain fire retardants. We also evaluated the extent to which the closure system used to attach multiple panels impacted IWC burning behavior.”
Given the scale of IWC systems—most are used in ceiling-to-floor installations in large warehouses—the 16-ft. (4.9-m) high parallel panel test (PPT) was chosen as the best available method for the fire hazard evaluation (see figure 1). The traditional 16-ft. PPT was modified to simulate the typical IWC installation characteristics. The IWC samples, measuring 16 ft. high by 3.5 ft. (1.1 m) wide, were mounted on the PPT metal frame and held 1.75 ft. (0.5 m) apart.
A propane burner at the base of the test frame was used to deliver a 200 kW fire exposure for 15 minutes. After the burner is turned off, the test panels are observed for another five minutes for remnant burning. All PPT tests are conducted under the 5 MW fire products collector (FPC) in order to measure the heat release rate and the smoke generation rate.
“Most of our test samples were of R6 insulation value because, according to some manufacturers, that is the most sought-after model,” Agarwal says. “The pass/fail recommendations for the fire propagation and the smoke generation were developed based on the hazards associated with application of IWC products in industrial warehouses.”
Performance-based Standard
The new Approval Standard for IWC systems incorporates the test criteria established by the research program. Standard 4883 provides fire performance requirements for IWC systems for use in facilities that already have adequate sprinkler protection. Approved IWC systems will be listed in FM Approvals’ web-based Approval Guide, with specific height/usage guidelines, including two levels of classification relating to smoke generation: 1) use in smoke-sensitive occupancies such as cleanrooms and 2) use in smoke-sensitive occupancies such as food processing or pharmaceutical production.
The new standard includes:
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Flammability Characterization. The FM Approvals bench-scale fire propagation apparatus (FPA) will be used to determine the chemical heat of combustion, smoke yield, critical heat flux for ignition, thermal response parameter, fire propagation index and smoke development index.
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Modified 16-ft. Parallel Panel Test. Samples exposed to a 200 kW propane source in the modified 16-ft. PPT must show a peak charred height of less than 10 ft. (3 m) in order to pass this test. Based on the maximum chemical heat release rate measured in this test, products will be Approved for use with either no height restrictions or use to a maximum of 50 ft. (15.2 m). In addition, the average smoke emission rate measured during the PPT will be used to determine the smoke sensitivity rating.
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Surface Burning Characteristics. This optional test will be conducted at the request of manufacturers who wish to satisfy certain building code requirements and/or for identification purposes. A minimum of three tests will be conducted on IWC samples at a thickness of 4 in. (102 mm) or the product’s maximum thickness, whichever is less. Flame spread and smoke developed will be reported.
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Operational Requirements. Manufacturers must demonstrate a quality assurance program and associated documentation, submit to initial and follow-up surveillance audits, allow field inspections of installations and agree to notify FM Approvals of any future changes in product construction, components, raw materials and other factors.
“Flammability characterization using the Fire Propagation Apparatus (FPA) is required for all insulated wall curtain testing; however, those results will not have any bearing on the overall product Approval,” notes FM Approvals advanced materials engineer Dan Brown who is the author of FM 4883. “For IWC products, the FPA results are used as a sort of a fingerprint or snapshot of a product’s flammability characteristics at a point in time. Later, if a manufacturer proposes a change in the product, we can re-evaluate it using the FPA, which is a small-scale test, without—in most cases—having to run the PPT again.”
Cindy Frank, assistant vice president and manager of FM Approvals’ building materials group, adds, “Our research testing showed that these products can pose a risk. Our new Approval Standard will provide a way for manufacturers to distinguish their insulated wall curtain systems from others on the market and give building owners FM Approved choices that best match their loss prevention goals.”