Fire test methods flame spread

Measurement of flame spread under external heat flux is necessary where the thermal radiation is likely to impinge on the textile materials, for example, the flooring material of the building or transport vehicles whose upper surfaces are heated by flames or hot gases, or both. The French test method, NF P 92-503 Bruleur Electrique or M test involves radiant panel for testing flame spread of flexible textile materials. This test method (flame spread under external heat flux) is the basis of that used by the FAA (Federal Aviation Administration) for assessing flammability of textile composites used in thermal/acoustic insulation materials (FAR 25.856 (a)) used in aircraft and has also been included by the EU for fire test approval of floorings such as prEN ISO 9239 and BS ISO 4589-1. 

A number of fire tests for polymeric materials have been developed, during the past several years, by the International Standards Organization (ISO). Hopefully, these tests will replace the present national test methods, which often correlate badly with each other. I he development at ISO is aimed at describing the fire properties of polymeric materials comprehensively, with test methods chosen so as to be applicable to all types of samples. At present, the ISO fire test methods are published as standards (ISO R 1182-79 for non-combustible materials, ISO R 1326-70 and ISO R 1210-70 for flame spread, etc.), or as draft for development (DP 5657, ISO/TC 92 N 531-79 as an ignitability test). One can only sympathize with using certain complex fire hazard indices for describing material behavior in fire... 

The severity of the exposure and the time a specimen is exposed to the ignition source are the main differences between the tunnel test methods. The 25-ft tunnel test is the most severe exposure and the specimen is usually exposed for 10 min. An extended test of 30 min is performed on fire-retardant treated products. Materials that pass the extended test (have flame spread less than 25 with no evidence of glowing) qualify for a special FR-S rating. Because the 25-ft tunnel test is the most severe exposure it is used as the standard for building materials. The 2-ft tunnel test 17, 18) is the least severe. Because of the small specimen size required with this test, it is a valuable tool for development work on fire retardants. The 8-ft tunnel falls between the 2- and 25-ft tunnels in severity. It can be a valuable... 

Basic Mechanisms. Finally, further work is necessary on fundamental mechanisms of individual fire retardants. These mechanisms are a function of the particular chemicals involved and the environmental conditions of the fire exposure. There is a need to establish common methods and conditions for determining these mechanisms in order to compare different treatments. This would give us a better understanding of how these compounds work in action and would provide a more efficient approach for formulating fire-retardant systems than a trial and error approach. Correlations also need to be established between rapid precise thermal analysis methods and standard combustion tests. Retardant formulations could be evaluated initially on smaller (research and development size) samples. The more promising treatments could be tested for flame-spread index, heat release rate, and toxic smoke production. 

Fire-test method development has followed two separate but complementary paths. One path, theoretically oriented, is characterized by the measuring of scientifically-meaningful fire properties, such as mass loss and rate-of-heat release. This approach also includes the development of mathematical models incorporating these properties to predict propagation and flame spread. A new lab-scale apparatus, the "cone calorimeter" developed at NIST is an example of the hardware now available to measure these fire properties. 

Note 1 ASTM s policy is not to use descriptive terms such as nonflammable, flame retardant, self-extinguishing, non-burning, and similar. According to ASTM, results of any of fire test methods must be described in numbers, such as flame spread index of 75, or flame spread index below 200, or a burning rate of... 

ASTM E132 was developed as an improvement on the apparatus in ASTM E162 [38]. The specimen size for flame spread studies is 155 by 800 mm by a maximum thickness of 50 mm. This test method determines the critical flux for flame spread, the surface temperature needed for flame spread and the thermal inertia or thermal heating property (product of the thermal conductivity) test. These properties are used mainly for assessment of fire hazard and for input into fire models. A flame spread parameter is also determined, and this can be used as a direct way of comparing the responses of the specimens. It has been used for predictions of full-scale flame performance [39]. 

A description is given of the initiatives carried out within the European Community for the harmonization of fire testing. The technical and economic reasons are explained for such initiatives, which are taken in order to remove barriers to trade from the European internal market. Of the various fire aspects, only fire reaction testing is taken into consideration here, because it appears as a major technical obstacle to the free circulation of construction materials. All possible approaches are considered for the attainment of such a harmonization and one, the so called interim solution, is fully described. The proposed interim solution, is based on the adoption of three fundamental test methods, i.e. the British "Surface Spread of Flame", the French "Epiradiateur" and the German "Brandschacht", and on the use of a rather complicated "transposition document", which should allow to derive most of the national classifications from the three test package. 

A typical criticism of this test method, for example, is that ordinary newsprint, and even tissue paper, will meet its requirements. That is a valid criticism. However, there seems to be general agreement that, in spite of its lack of sophistication, this test method has been successful in eliminating the fabrics with the poorest fire performance from the general population of fabrics in use for apparel in the United States. Thus, fabric types such as the fibrous torch sweaters with raised surface fibers that ignite readily and spread flame quickly are no longer legally sold in the United States due to the test requirements. The test has also been able to screen out the use of very sheer... 

EN 50399, Common test methods for cables under fire conditions—Heat release and smoke production measurement on cables during flame spread test—Test apparatus, procedures, results, European Committee for Standardization, Brussels, Belgium. 

For textile materials used as interior wall-coverings in U.K. buildings including railway carriages, where the fabric could be in a vertical orientation attached to the wall panel, measurement of rate of flame spread under external heat flux is one of the requirements. For such applications, the test method (BS 476 Part 7) essentially requires a vertically oriented specimen exposed to gas-fired radiant panel with incident heat flux of 32.5kW/m2 for lOmin. In addition, a pilot flame is applied at the bottom corner of the specimen for 1 min 30 s and rate of flame spread is measured. The same principle is used in the French test for carpets, NF P 92-506. 

BS 476 Part 7 1987 Fire tests on building materials and structures Method for classification of the surface spread of flame of products. 

The Steiner Tunnel test (ASTM E 84) is used to classify the fire-spread potential of products used in wall and ceiling linings [4], and is used to classify expanded polystyrene foam. In this method, specimens are placed on the ceiling of a 24 ft long tunnel. An 88 kW natural gas burner is placed at one end of the tunnel and a forced-air draft with a velocity of 1.22 m/s is introduced. The flame spread is recorded as a function of time and an arbitrary index is calculated from the measurements. 

ASTM E 84 Steiner Tunnel Test. This test, which uses very large samples (20 ft x 20 1/4 in.) is referenced in all model building codes for evaluating flame spread and smoke emission of foam plastic insulation. The test apparatus consists of a chamber or tunnel 25 ft. long and 17 3/4 X 17 5/8 in. in cross section, one end of which contains two gas burners. The test specimen is exposed to the gas flame for ten minutes, while the maximum extent of the flame spread and the temperature down the tunnel are observed through windows. Smoke evolution can also be measured by use of a photoelectric cell. The flame spread and smoke evolution are reported in an arbitrary scale for which asbestos and red oak have values of 0 and 100, respectively. More highly fire-retardant materials have ratings of 0-25 by this method. 

ASTM E1321-09 (standard test method for determining material ignition and flame spread properties) and ISO 5658-1 2006 and ISO 5658-2 2006 (reaclion-to-fire tests - spread of flame - part 1 guidance on flame spread and part 2 lateral spread on building and transport products in vertical configuration) for flame... 

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