This test method provides a description of the behavior of material specimens under a specified fire exposure in terms of the release rate of heat and visible smoke. It is possible to determine the change in behavior of materials and products with change in heat-flux exposure by testing specimens in a series of exposures that cover a range of heat fluxes.
The data obtained for a specific test describe the rate of heat and smoke release of the specimen when exposed to the specific environmental conditions and procedures used in performing that test.
The entire exposed surface of the specimen will not be burning during the progressive involvement phase when piloted, point ignition (impingement) procedures are used. During the period of progressive surface involvement, release rates of heat and smoke are “per square metre of original exposed surface area” not “per square metre of flame involved surface.”
The rates of both heat and smoke release are calculated per square metre of original surface area exposed. If a specimen swells, sags, delaminates, or otherwise deforms so that the exposed surface area changes, calculated release rates correspond to the original area, not to the new surface area.
Heat-release values depend on mode of ignition. Gas phase ignition gives a more dimensionally consistent measure of release rate when very rapid or immediate flame involvement of the specimen surface occurs. However, piloted, point ignition allows release-rate information to be obtained at external heat flux from zero up to that required for satisfactory gas-phase ignition, usually over 20 kW/m2 external exposure. No correlation between the two modes of piloted ignition has been established.
Release rates depend on many factors, some of which cannot be controlled. It is possible that samples that produce a surface char, a layer of adherent ash, or those that are composites or laminates do not attain a steady-state release rate. Thermally thin specimens, that is, specimens whose unexposed surface changes temperature during period of test, will not attain a steady-state release rate. Therefore, release rates for a given material will depend, for example, on how the material is used, its thickness, and the method of mounting.
Heat-release values are for the specific specimen size (exposed area) tested. Results are not directly scalable to different exposed surface areas for some products.
The method is limited to specimen sizes of materials in accordance with 7.1 and to products from which it is possible to obtain a test specimen representative of the product in actual use. The test is limited to exposure of one surface; there are two options for exposure orientation: either vertical or horizontal. If a heat release rate of 8 kW, which is equivalent to 355 kW/m2 for 150 by 150-mm vertical specimens, or 533 kW/m2 for 100 by 150-mm horizontal specimens is exceeded, there is danger of combustion occurring above the stack.
No general relationship between release rate values obtained from horizontally and vertically oriented specimens has been established. Conduct tests on specimens in the form in which the material is oriented in end use conditions. To provide additional information, conduct tests in the horizontal orientation for those specimens that melt and drip in the vertical orientation.
Release rate measurements provide useful information for product development by giving a quantitative measure of specific changes in fire test performance caused by product modifications.
This test method differs in both the method of exposure and the calculation procedure from the techniques used in Test Method E 1354
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