5.1 This test method provides a means for screening materials, products, or assemblies, for the mass loss, and ignitability they exhibit under specified heat flux exposure conditions. As an option, the test method is also suitable for screening for the heat released, by using a thermopile method (See Annex A2).

5.1.1 Terminology E176, on fire standards, states that fire-test-response characteristics include ease of ignition and mass loss (both measured in this test method), as well as flame spread, smoke generation, fire endurance, and toxic potency of smoke.

5.1.2 The mass loss rate of a material, product, or assembly is a fire-test-response characteristic that gives an indication of its burning rate. Thus, a lower mass loss rate is often associated with slower burning. Note, however, that mass loss is not always a result of combustion, and that this method does not assess release of smoke or combustion products.

5.1.3 The time to ignition of a material, product, or assembly is a fire-test-response characteristic that gives an indication of its propensity to ignite at the applied heat flux level and subsequently to release heat and spread flame over its surface. Thus, a longer time to ignition is an indication of a lower propensity for the material, product, or assembly to become involved and contribute to fire spread or growth; however this method does not assess the smoke or combustion products released.

5.1.4 The apparatus used for this test method is suitable to assess the critical heat flux for ignition of the materials, products, or assemblies tested, by assessing ignitability at various heat fluxes (see Appendix X3 for guidance).

5.2 Values determined by this test are specific to the specimen in the form and thickness tested and are not inherent fundamental properties of the material, product, or assembly tested. Thus, closely repeatable or reproducible experimental results are not to be expected from this test method when tests are conducted for a given material, product, or assembly, while introducing variations in properties such as specimen thickness or density.

5.3 No incident irradiance is specified in this test method. The instrument is capable of generating irradiances ranging up to 100 kW/m². The choice of irradiance is a function of the application of the material, product, or assembly to be tested, and of the fire scenario the user is investigating. However, the method is not suitable for incident irradiances below 10 kW/m³ (see 5.7.3).

5.4 The method used for optionally measuring heat release, a thermopile, is not as accurate as the conventional oxygen consumption calorimetry method, used in the cone calorimeter, Test Method E1354, in its applications standards, such as Test Method E1474 and E1740, or in intermediate scale or a large scale calorimetry test methods, such as Test Methods E1623, E1537, E1590 or D5537 (see also Annex A2). On the other hand the thermopile method of assessing heat release has been used extensively because of its simplicity, including Test Method E906, and other applications discussed in Guide E603.6

5.5 Testing of composites and dimensionally unstable materials requires special procedures (see 8.4 and 8.5).

5.6 Testing in the vertical orientation is feasible with the test method, but not recommended, as it has been shown to have the potential to lead to serious measurement errors on time to ignition.

5.7 Limitations 

5.7.1 No universal formula exists for calculation of heat release as a function of mass loss. If heat release data are desired, calibration curves must be developed by the user, and they are specific to the material, product, or assembly tested.

FIG. 1 Schematic of Apparatus

5.7.2 If during the test of one or more of the three replicate test specimens, any of the following unusual behavior occurs: (1) molten material overflows the specimen holder trough, (2) one or more portions of a test specimen is forcefully displaced from the zone of controlled irradiance (explosive spalling); or (3) the test specimen swells sufficiently prior to ignition to touch the spark plug or swells up to the plane of the heater base during combustion; the test is invalid. Then test an additional specimen of the identical preconditioned test specimens in the test mode in which the unusual behavior occurred. Do not incorporate data obtained from the tests noted above, yielding inadequate results, in the averaged data but report the occurrence. The test method is not suitable if more than three out of six test specimens tested show any of the above characteristics.

5.7.3 The applicability of this test method to smoldering ignition has not been demonstrated. This test method is not suitable for incident irradiances below 10 kW/m².

5.7.4 The validity of the results of this test method for a particular scenario depends on the conditions under which the tests are conducted. In particular, it has been established that the use of a different irradiance will change relative results

5.7.5 The thermopile readings, if used, are likely not to be reflective of the heat output of the burning specimen if the flames extend to the thermopile.

5.8 In this procedure, the specimens are subjected to one or more specific sets of laboratory test conditions. If different test conditions are substituted or the end-use conditions are changed, it is not always possible by or from this test method to predict changes in the fire-test-response characteristics measured. Therefore, the results are valid only for the fire test exposure conditions described in this procedure.

Note 1: This statement is required for all fire-test-response standards by Practice E535.