Turning the Corner on Wall Testing

Historical knowledge base makes accuracy possible through smaller, less expensive tests

Throughout its 130-year history, FM Approvals has consistently applied the many resources at its disposal to develop new product certification standards and refine existing standards in order to increase the variety and availability of FM Approved loss prevention products. Nowhere is this more evident than in the evolution of FM Approvals’ wall testing standards: Approval Standard 4880, Class 1 Fire Rating of Insulated Wall or Wall and Roof/Ceiling Panels, Interior Finish Materials or Coatings, and Exterior Wall Systems, and Approval Standard 4881, Class 1 Exterior Wall Systems.


There is a need for tested and certified building products worldwide. We are reminded of this when we see reports from around the world of catastrophic fires involving combustible exterior wall panels, particularly those used on high-rise buildings in the Middle East and Asia. We see this need, as well, when buildings are destroyed, their roofs and walls breached by high winds and windborne debris from tropical cyclones and other wind events.


FM Approved exterior wall systems must meet both Standard 4880 for fire performance and Standard 4881 for resistance to natural hazards such as wind, hail, and windborne debris. These standards are prime examples of the way FM Approvals works to fulfill its mission to encourage the development of FM Approved products that improve and advance property loss prevention. Standard 4880, introduced in 1973, is one of FM Approvals’ earliest formalized fire test standards for wall systems. This standard has been transformed dramatically over time to the benefit of both manufacturers and end users. Let’s take a look at this evolution.


Small-scale testing leads to large-scale benefits

FM Approvals has a long history with transitioning from large-scale tests to intermediate or even small-scale testing. A classic example is the roofing assembly test for exposure to interior fires. In 1954, roof assemblies were tested in a large (10 ft. [3 m] high x 10 ft. [3 m] wide x 100 ft. [30.5 m] long) apparatus known as the White House Test. While accurate, the test took time to assemble and was expensive to conduct. The scaled-down equivalent, the construction materials calorimeter (CMC), developed in 1957, allowed for faster and less expensive testing. The CMC test apparatus not only provided important product performance information, but also highlighted the benefits offered by small-scale tests that could be accurately correlated through research to their large-scale cousins, resulting in faster testing and lower costs.


In the early 1970s, the need for improved wall panel testing became a priority due to the rise in use of foamed plastics as insulation for wall and ceiling panels. Energy efficiency was a national imperative thanks to the oil crises of the 1970s that led to rapid price hikes in oil prices. Foam plastic insulation offered a low-cost, lightweight way to reduce facility energy costs. However, many of the small-scale fire tests used at the time to evaluate these foamed plastics did not provide an accurate view of their fire performance in actual construction configurations.


In 1972, FM Approvals and FM Global Research developed the 25-ft. (7.6-m) full-scale corner test (figure 1) to accurately evaluate the fire hazards associated with wall and/or wall and ceiling assemblies for industrial and commercial buildings. This large-scale test was designed to determine the fire performance of materials under conditions and scales typically found in large warehouses, factories, office buildings and other structures.



One of the first research applications of the 25-ft. corner test was a study conducted under the auspices of the Society of the Plastics Industry to evaluate rigid cellular plastic materials for insulated wall and/or roof/ceiling construction. One of the motivating factors for this research was the concern that small-scale tests—such as the ASTM E-84 tunnel test—did not reliably and consistently reflect the fire performance of foamed plastics under actual conditions.


The research confirmed the original suspicion that a flame spread rating of less than 25 in the E 84 test for foamed plastics did not correlate to actual building fire performance of wall or ceiling foamed plastic products. It was further determined that the immediate adoption of the full-scale 25-ft. corner test for wall and ceiling assembly testing and certification was essential.


From 1973 through 1987, the 25-ft. corner test became the heart of Approval Standard 4880, for applications with ceiling heights up to 30 feet (9.1 meters). However, the march of progress (and improvements in industrial material handling systems) brought ever higher warehouse storage heights. Soon, wall and ceiling panel manufacturers were pushing for certification for use of their products in applications up to 50 feet (15.2 m) and higher.


In 1987, the 50-ft. version of the corner test was introduced and enabled FM Approvals to provide full-scale testing for certification for applications up to 50 feet and beyond.


At this point in the history of FM Approvals wall testing, the cost and time required for a certification program was a cause for concern. A single full-scale corner test took at least a month to prepare, conduct and tear down. This testing required significant labor and laboratory space at the FM Global Research Campus. The cost—between US$100,000 and US$200,000—and time required for testing was also becoming an impediment to small manufacturers attempting to enter the market, particularly in regions outside North America.


“Our mission is to encourage the development and use of FM Approved products that improve and advance property loss prevention around the world,” observes Rich Ferron, FM Approvals operations vice president and manager of testing and certification services. “At that point in our history—the early 1990s—we could not fully realize our mission by relying on large-scale fire testing for every wall test program. We had an opportunity to make major improvements using the many tools at our disposal, including ongoing research, practical observations from the field, and collaboration with manufacturers and end users.”


A turning point came in 1994 when FM Approvals made important changes in Standard 4880 with the addition of a new small-scale test—the fire propagation apparatus (FPA). The FPA—also known as ASTM E 2058 or NFPA 287—allowed manufacturers to optimize the wall core material in a small-scale, low-cost, timely fashion as opposed to conducting full-scale corner tests to determine which core was the best to produce. 


At the same time, an intermediate-scale room fire test was added to Approval Standard 4480. For wall and ceiling panels, this important test measures the flashover phenomenon, flame spread, smoke intensity and joint integrity; burning droplets or particles are also observed. Ferron notes, “The room test became even more important as a way to evaluate how wall panel joints, for instance, will react in a fire and to gain a better understanding of flame spread both vertically and horizontally.”


The 25-ft and 50-ft full-scale corner test remained part of Approval Standard 4880 until 2009 for manufacturers seeking Approval for wall and ceiling systems. At that point, an important new test apparatus was added to the standard—the 16-ft. (4.9-m) parallel panel test (PPT). Various forms of the parallel panel test had been used since the early 1980s as a demonstration and research tool. In the late 1980s, the PPT was used to evaluate, among other things, the fire propagation behavior of electrical cables and in 1997, the 8-ft. (2.4-m) PPT was included as part of the innovative new Approval Standard 4910, Cleanroom Materials Flammability Test Protocol.


Based on extensive research that compared fire test results obtained from hundreds of 25-ft. and 50-ft. corner tests with results from the 16-ft. parallel panel tests, FM Global and FM Approvals staff determined that the 16-ft. PPT provides an accurate and reliable intermediate-scale fire test that correlates well to the full-scale corner tests for wall panels with thermoset cores.


In 2009, the 16-ft. version of the PPT (figure 2) was included in a revision of Approval Standard 4880 to replace, in most cases, the need for full-scale corner testing. The parallel panel test used in Standard 4880 features two vertical panels measuring 16 feet high (4.9 meters) by 3.6 feet (1.1 meters) wide and spaced 21 inches (.53 meters) apart. A propane sand burner is located at the base between the panels and is used to generate an ignition source of 360 kW.



The introduction of research-proven small- and intermediate-scale tests—FPA, PPT and room fire test—in Approval Standard 4880 has resulted in significant benefits for both manufacturers and end users, including:

  • Most full-scale fire tests eliminated, thanks to the correlation of more than 100 large-scale fire test results with small- and intermediate-scale data
  • A significant reduction—at least 50 percent in most cases—in testing and certification costs for manufacturers
  • A major reduction in testing and certification cycle time (up to 75 percent for many programs)
  • Increased availability and lower cost/time for sample screening tests


These and other benefits that have resulted from the shift by FM Approvals from large-scale fire testing to small- and intermediate-scale testing have led directly to increases in the number of FM Approved products available.


A natural addition to wall testing

The need to test exterior walls and ceiling panels does not end with fire testing. FM Approvals recognized the need for exterior wall systems to provide protection against a host of natural hazards. In 2007, FM Approvals introduced a new standard—Approval Standard 4881—designed to evaluate the resistance of exterior wall assemblies to natural hazards such as wind, hail and windborne debris.


Standard 4881 requires all wall systems to attain a Class 1 fire rating in accordance with Approval Standard 4880. Other tests required by FM 4881 include static and cyclic wind loading, windborne debris with optional small or large objects, and hail resistance.


Aside from the required Class 1 fire rating, Approval Standard 4881 provides a range of Approval ratings that allow manufacturers to target exterior wall systems for almost any geographic area, up to and including hurricane- and cyclone-prone regions. The rating choices provided by the standard enables end users to select the most cost-effective FM Approved solutions to meeting their building envelope requirements.


For instance, for a wall system to be certified under FM 4881 for use in hurricane-prone zones (H and HM), it must pass a cyclic wind loading test that subjects the sample to more than 9,000 cycles of positive and negative air pressure. In addition, the manufacturer may elect to qualify its wall system for windborne debris resistance in two categories: large or small missile.


The large missile impact test subjects the wall system to two impacts from an 8 ft. (2.4 m.) long wooden 2x4 weighing 9 lbs. (4 kg), fired from an air cannon and traveling at about 35 mph (15.25 m/s). The small missile test impacts the wall sample with 10 steel balls weighing 0.07 oz. (2 g) fired at a speed of approximately 90 mph (39.6 m/s).


Hail resistance testing is also required under FM 4881. Manufacturers may choose between two levels of hail testing: Severe (S) and Moderate (M). The severe hail test uses 1.75-in. (44-mm) diameter ice balls fired at the test wall assembly

(figures 3 and 4) at a speed of approximately 69 mph (31 m/s). The moderate hail test uses a 1.5 in. (38 mm) diameter ice ball.




The completion in 2009 of a new 72,000-ft2 (6,690-m2) Natural Hazards Laboratory in West Glocester, Rhode Island, USA, helped accelerate wall testing programs by providing needed space for wall and roof system testing.


Continuing evolution of wall standards

Two of the newest Approval Standards for wall system testing are Approval Standard 4882, Class 1 Interior Wall and Ceiling Materials or Systems for Smoke-Sensitive Occupancies, and Approval Standard 4411, Cavity Walls and Rainscreens. Both of these standards are not only founded in strong prior research, but also based on new research programs initiated to solve specific new wall testing challenges. To learn more about the newly introduced Approval Standard 4411, follow this link for a complete overview.


Approval Standard 4882, introduced in 2010, sprang from a need identified by FM Global for interior wall and ceiling materials or systems that could meet the cleanliness requirements of industries such as food processing and pharmaceuticals, but still provide effective fire resistance and minimal smoke generation.


“The food and pharmaceutical industries use powerful chemicals to clean their facilities so the walls need to be lined with a material that can stand up to constant washing,” Ferron explains. “Typically, the walls would be made of a plastic material. The common plastics used several years ago posed a fire hazard because they were combustible, in most cases, and presented issues with generating high amounts of smoke in the event of a fire. There was clear need was for a product that did not yet exist in the marketplace.”


Ferron explains that FM Approvals reached out to the makers of plastic products that had been certified in accordance with Standard 4910, Cleanroom Materials Flammability Test Protocol. Since the standard was introduced in 1997, hundreds of products Approved to Standard 4910 have entered the market and are used in the semiconductor industry, and in other industries that rely on cleanrooms, including pharmaceutical and chemical companies.


“We worked with one of our leading manufacturers to conduct a research program to investigate what it would take to produce a product that fell between the requirements of Standard 4910 and the Class 1 fire rating under Standard 4880,” Ferron notes. “We ultimately were able to differentiate a new wall product based on smoke and flame generation. So, we had all the tools in place for this new standard—the FPA, the room test, and the Parallel Panel Test. We worked hand-in-hand with research, engineering standards, and end users for real-world feedback as to the product performance.”


The first wall systems Approved in accordance with the new Approval Standard 4882 quickly found homes in many food and pharmaceutical facilities around the world. In fact, these products were installed in more than 50 FM Global insured locations from 2010 through 2013 (the most recent year for which data is available), resulting in a reduction of more than half a billion (U.S.) dollars in loss expectancy. 


Paris Stavrianidis, FM Approvals vice president, general manager and 40-year veteran of Approval testing and research, notes, “We have developed more than 200 Approval Standards, which have resulted in more than 60,000 Approved products, some of them representing completely new loss prevention products brought to life, in large part, by our efforts. All of our standards are rooted in fundamental and applied research, and driven by actual loss prevention needs that have been identified by our field organization. In addition, we provide our standards and much of our other loss prevention information for free for the common good. We are the only testing and certification organization in the world that operates in this way.”