Fire test methods incident flux

In the early 1980s, Vytenis Babrauskas, at the NIST (then NBS), developed a more advanced test method to measure RHR the cone calorimeter (ASTM E 1354).71164 This fire test instrument can also be used to assess other fire properties, the most important of which are the ignitability (as discussed earlier), mass loss, and smoke released. Moreover, results from this instrument correlate with those from full-scale fires.165-170 To obtain the best overall understanding of the fire performance of the materials, it is important to test the materials under a variety of conditions. Therefore, tests are often conducted at a variety of incident heat fluxes. The peak rates of heat release (and total heat released) of the same materials shown in Table 21.15 at each incident flux, are shown in Table 21.16.147... 

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. 

For the purpose of this article, fire tests are associated with the second strategy and defined as experimental methods to characterize the behavior of polymers under more severe thermal exposure conditions that are representative of the growth phase of a compartment fire. These conditions are simulated with a gas-fired or electrical heater or a large gas burner turbulent diffusion flame (flame length of the order of a meter or several feet). The incident heat flux to the specimen is primarily radiative when heaters are used, and mainly convective for flame exposure. Total incident heat flux varies from approximately 1 kW/m to more than 100 kW/m. Note that the maximum radiant heat flux from the sim on earth is approximately 1 kW/m. Polymers that are not treated with fire retardant chemicals typically ignite when exposed to heat fluxes of 10-20 kW/m in the presence of a small pilot flame or hot spark. 

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