Because of their potential to serve as the primary fuel driving an enclosure fire to flashover, the flammability characteristics of interior wall and ceiling finishes have been regulated for more 50 years. In this paper, the roles of interior finishes in fire development are addressed. An historical of the significant fires that shaped the regulation of interior in the United States is presented. scientific understanding of fire spread over interior finishes has developed over the past 25 years, with the quantitative methods needed evaluate the fundamental flammability properties of materials. Theoretical associated with flame spread are presented in the following These concepts demonstrate to a large extent, flame spread on finishes can be viewed as a race the ignition and burnout of surface elements. Finally, a new way evaluating, and perhaps eventually the flammability characteristics combustible interior finishes is presented. This methodology provides way to move away from the current basis for the regulation of finish flammability to a more quantitative scientific basis.

HISTORICAL PERSPECTIVE
As a result of a number of major widely publicized building fires in United States during the 1940s, including the Cocoanut Grove fire2 in Boston, the LaSalle Hotel fire 3 in Chicago, and the Hotel Winecoff fire 4 in Atlanta, the role of interior finish in fire development became more widely recognized in the fire protection engineering and building regulation communities than it had been previously. That these fires occurred in buildings of so-called "fireproof" construction highlighted the contribution of the interior finishes and decorations to these fires.

Following the Cocoanut Grove fire in 1942, but before the LaSalle Hotel and Hotel Winecoff fires in 1946, A. J. Steiner of Underwriters' Laboratories published a test method to classify the hazards of building materials. 5 As noted by Steiner 6 apparently in reference to the Cocoanut Grove fire, "Public concern is aroused periodically when a rapidly spreading fire kills a large number of people or produces an extraordinary property loss. This concern prompted the development of a test method whereby the fire hazards of materials could be measured and classified with reference to the rate of spread of fire, the amount of fuel contributed to the fire, and the production of objectionable smoke while burning." This test method is now widely known as the "tunnel test" because of the duct-like configuration of the fire test chamber or as the "Steiner tunnel test" in honor of its principal developer.

In 1950, ASTME84-50T, Tentative Method of Fire Hazard Classification of Building Materials, 7 was first approved by the American Society for Testing and Materials as a tentative standard. This test method was adopted by all the model building codes in the United States and by the NFPA Building Exits Code (now the Life Safety Code), resulting in wide-spread regulation of the "flame spread" and "smoke development" of interior wall and ceiling finishes based on tunnel test results. The tunnel test remains the primary fire test method used to regulate the flammability of interior wall and ceiling finishes in the United States more than 50 years later, despite recognition of its technical shortcomings and the development of more realistic fire test methods for interior wall and ceiling finishes.

In 1950, Factory Mutual Laboratories (FM) published a report 8 describing a room fire test method to evaluate the life hazard of interior finishes. In the after-math of the large life-loss fires of the 1940s identified above, this report noted that, "There is considerable agitation at the present time to write regulations governing the use of interior wall and ceiling finish materials, in the interest of reducing the life hazard in public areas where these materials are used in quantity. Before adequate and equitable regulations can be established, fire conditions constituting a life hazard will, of necessity, need to be defined and materials tested under such conditions of exposure." FM developed a test room approximately 4.2 m (14-ft.) by 6.1 m (20-ft.) by 3.7 m (12-ft.) high. FM experimented with a number of ignition sources consisting of wood cribs weighing from 2.3 kg to 13.6 kg (5 lb to 30 lb) and/or ethyl alcohol weighing from 0.2 kg to 3.4 kg (1 lb to 7.5 lb) placed in a corner of the room.

The conclusion of the FM report was that the ignition source consisting of 7.5 lb of wood and 0.75 lb of alcohol was considered to be "the most suitable exposure in this enclosure for establishing the extent to which interior wall and ceiling finish materials contributed to produce a life hazard. Several factors influenced the selection of this exposure: 1) It was of sufficient intensity to ignite materials causing them to burn and contribute to the rise of temperature within the enclosure. 2) Its location in one corner of the room adjacent to two walls produced a maximum exposure condition to wall and ceiling material. 3) It was the largest test exposure that could be used without producing a life hazard in the test enclosure by the burning of the enclosure itself. 4) This exposure ... produced a temperature of 155°F (68°C) at the breathing level, which was sufficiently below the chosen life hazard temperature of 300°F (150°C) to determine to what extent the wall or ceiling material would contribute a life hazard."

This FM report is significant for a number of reasons. It represents one of the first systematic efforts to evaluate the flammability of interior wall and ceiling finishes in an end-use configuration. It recognizes that fires located in corners represent a realistic worst-case exposure geometry for wall and ceiling linings. It establishes a selection process for ignition sources that challenge the materials being evaluated but do not overwhelm their performance. Unfortunately, the room fire test method developed by FM to evaluate the life hazard of interior finishes never gained the widespread acceptance within the building regulatory community that the tunnel test did.

Through the 1950s, the tunnel test method became more firmly entrenched as the standard for regulating the flammability characteristics of interior finish materials despite the fact that it only had tentative status under ASTM. During this period, the use of plastics in building construction also started to grow tremendously. Both Steiner9 at UL and Wilson10 at FM voiced concern with the small-scale laboratory procedures, such as ASTM D635 and D1692, and the terminology, such as "self-extinguishing," "slowburning," and "nonburning," being used to evaluate and describe the flammability performance of plastic building products.

Wilson noted that these small-scale laboratory tests are "intended solely for comparing the relative flammability of various plastic materials," and that they "are neither designed nor appropriate for the rating of plastic products as building materials." Steiner noted that "the tests which classify plastics as self-extinguishing and slow-burning do not correlate with the Fire Hazard Classification. To illustrate, some time ago a plastic which had been classified as slow-burning was subjected to the tunnel test, and the results were disastrous. The material burned so fiercely and created so much smoke and molten residue that it took days to clean up and repair our furnace. Need for action by a fire protection group is essential to control the fire hazard being created." Steiner went on to say that "the value of results of a test are dependent on their significance as related to their use, based on actual field fire experience."

Steiner was a proponent of small-scale tests as "effective instruments for development and research, as well as tools for inspection," but he also recognized their limitations: "The small-scale tests can be used in the examination of products to determine whether they provide the same properties as other materials tested in the same manner ..., but they do not provide fire protection information on the behavior of the product, or of assemblies employing it, under actual use conditions in buildings." He goes on to say that "the same fire protection engineering considerations must be given to all tests, whether small or large. The results must be representative of actual conditions, the classifications must be realistic and the requirements consistent." It is interesting to note that Steiner11 viewed the tunnel test as a large-scale test, while others12 have viewed the tunnel test as a small-scale test.

In 1961, Wilson13 reviewed a number of test methods then being used to evaluate the surface flammability of materials. Wilson noted that "None of the agencies developing these test methods has reported any relation between their test results and actual fire conditions. ... There has been nothing reported to indicate that four of the test methods (including the tunnel test) have ever been directly compared with any form of actual fire condition." Both Steiner and Wilson seemed to agree that the results of fire tests should be representative of actual conditions to be valid.

Through the 1960s, some of the technical shortcomings associated with the tunnel test began to be recognized more widely when the tunnel test was used to evaluate the flammability characteristics of newly developed foam plastic insulation products that were starting to be used in buildings. Some of these products received low flame-spread ratings in the tunnel test, yet rapidly spread fires when installed in buildings. This anomalous propensity for rapid flame-spread and fire development on exposed foam plastics despite low flame-spread ratings was demonstrated by newly developed open-corner fire tests14 that more realistically simulated the dynamics of enclosure fires than the tunnel test did. An example of this anomalous behavior is illustrated in Figure 1, which shows an open-corner fire test of a polyurethane foam insulation product with a low reported flame-spread rating.

As a consequence of the little-known Childress residence fire15 in which two children died as a result of a fire involving exposed polyurethane foam insulation installed in their home, the Federal Trade Commission (FTC) filed a proposed complaint16 against 27 respondents, including 25 manufacturers of foam plastic products and 2 trade organizations, the Society of the Plastics Industry (SPI) and the American Society for Testing and Materials (ASTM), claiming that the respondents were knowingly marketing foam plastic insulation products with misleading representations that such products were " nonburning" and "self-extinguishing" on the basis of inadequate test methods, including the tunnel test.

There was a great deal of activity during the year after the FTC proposed complaint was issued, which culminated in the "Complaint and Decision" of November 4, 1974, that included a Consent Decree signed by 24 companies and the SPI17. As part of the Consent Decree, the respondents agreed to perform many activities, which ranged from notifying all prior purchasers of foam insulation products of the dangers of the products to sponsoring and conducting research into the proper ways to protect foam plastic insulation products. These activities are summarized in the 1980 Final Report of the Products Research Committee, ¹⁸ which was formed to administer a $5 million trust fund established as part of the Consent Decree.

Between the time when the FTC Consent Decree was signed in 1974 and the PRC Final Report was issued in 1980, the use of thermal barriers to separate foam plastic insulation products from occupied spaces in buildings became the standard practice. For example, the 1973 edition of the Uniform Building Code (UBC) did not make any reference to foam plastics while the 1976 edition of the UBC included a new section (Section 1717) devoted exclusively to foam plastics. This new section generally required foam plastics to be separated from the interior of a building by a thermal barrier, such as 1/2 in. (13 mm) thick gypsum wallboard, having a finish rating of not less than 15 minutes unless specifically approved on the basis of " approved diversified tests," including "fire tests related to actual end-use such as a corner test." The details of a diversified test to be used for evaluating foam plastics were not specified until 1982.

Room fire test methods were used increasingly during the mid-to late-1970s as an alternative to the open-corner fire tests that had been used during the 1960s and early 1970s. In 1975, Underwriters Laboratories reported19 on a series of flammability studies of interior finishes that included room fire tests. In 1977, ASTM first published ASTM E603, Standard Guide for Room Fire Experiments. This document noted that, "There is no standard room fire test at the present time, and this report does not define one. It does set down many of the considerations for such a test: for example, room size and shape, ventilation, specimen description, ignition source, instrumentation, and safety considerations which must be decided upon in the design of a room fire experiment."

In 1979, Williamson and Fisher20 described efforts then underway at the University of California, Berkeley, to develop a standard room fire test method. They subsequently reported21 on their efforts to evaluate this room fire test method. They used an enclosure with dimensions of 2.4 m (8-ft.) wide by 3.7 m (12-ft.) long by 2.4 m (8-ft.) high, which was becoming the most typical enclosure size for room fire tests. This work and related work at other fire research laboratories resulted in a proposed ASTM standard room fire test method for wall and ceiling materials and assemblies22 in 1982, but this proposed standard was never adopted by ASTM.

In 1982, Uniform Building Code Standard No. 17-5, Room Fire Test Standard for Interior of Foam Plastic Systems, was first published to "detail a test method to evaluate the burning characteristics of foam plastic assemblies in a standard room configuration" and thus to serve as an approved diversified test for foam plastics under the UBC. This standard specified a room 2.4 m (8-ft.) wide by 3.7 m (12-ft.) long by 2.4 m (8-ft.) high with a doorway 0.8 m (2-ft. 6-in.) wide by 2.1 m (7-ft.) high centered in one of the 2.4 m (8-ft.) long walls of the enclosure. The ignition source specified for this test method was a 13.6 kg (30 lb) wood crib located 25 mm (1 in.) from a corner opposite the doorway opening.

During the 1980s, another series of hotel fires occurred that was reminiscent of those in the 1940s, except that these hotel fires involved modern high-rise buildings with interior finish materials that should have met modern regulatory requirements. The first of these hotel fires was the November 1980 fire at the MGM Grand Hotel23 located along the Las Vegas Strip in Clark County, Nevada. The early development of the MGM Grand fire was on the interior wall and ceiling finishes of a service side station in the deli restaurant on the casino level. ²⁴ Once the fire flashed over the side station, it quickly enveloped the deli restaurant, feeding on the combustible interior finishes and furnishings in the restaurant. The deli restaurant then flashed over, and the fire spread into and along the length of the casino, which was roughly the size of a football field. The fire was confined to the casino level, but 85 people died as a result of this fire, with approximately 68 of the victims located on the upper floors of the high-rise portion of the building above the casino.

Three months after the MGM Grand Hotel fire, the Las Vegas Hilton Hotel25 suffered a devastating fire that killed 8 people. This fire started in the 8th floor elevator lobby in the east wing of the 30-story building. The walls and ceiling of this elevator lobby, as well as all the other elevator lobbies on floors served by these elevators, were lined with a textile carpet material. The fire in the 8th floor elevator lobby developed to flashover, then spread from the 8th floor to the 28th floor of the building via the exterior windows located in each elevator lobby. The fire did not reach the 29th floor because of an architectural detail that deflected the flame out and away from the lobby windows.

The Las Vegas Hilton Hotel fire and other less-publicized fires involving textile materials motivated the textile industry to sponsor research at the University of California, Berkeley, to evaluate how well the tunnel test predicts the performance of textile wall coverings. ²⁶ As a result of this research project, a room fire test method for textile wall coverings was developed. This room fire test method was adopted as UBC Standard 42-2 in 1988 and is also currently designated as NFPA 265, which is referenced by the Life Safety Code and the International Building Code.

The fire at the DuPont Plaza Hotel27 in San Juan, Puerto Rico, occurred on December 31, 1986. This fire, which claimed the lives of 99 people located in the hotel's casino, started in a ballroom located across a covered foyer from the casino. The fire in the ballroom developed to flashover conditions on the new furniture being stored in the ballroom as well as on the textile wall material and foam-insulated movable partitions lining the walls of the ballroom. The combustible ceiling in the foyer also contributed to the fire development.

With the exception of the Las Vegas Hilton Hotel fire leading to the development of the room fire test method for textile wall coverings, the hotel fires of the 1980s did not inspire significant changes to interior finish requirements in the building regulations. Instead, these fires motivated the widespread use of automatic sprinkler protection in high-rise hotels and other residential and commercial buildings where sprinkler protection had not traditionally been installed.

The fire at the Station nightclub in West Warwick, Rhode Island, in February 2003 provides the latest extreme example of the role of interior finish in fire development. This fire, which claimed the lives of 100 victims and injured hundreds more, spread very quickly, primarily on the exposed convoluted flexible polyurethane foam material that had been installed on the walls and ceiling of the bandstand in the nightclub. This foam plastic product reportedly was intended for use as a packing material and therefore did not incorporate even a nominal amount of fire retardants. In light of the widespread recognition of the fire hazards associated with exposed foam plastic interior finishes and the regulation of the application of these products since the 1970s, it is difficult to comprehend how this application could have existed in 2003. It should serve as a reminder to fire safety professionals everywhere of the need for continual diligence.