5.1 This test method determines the response of textiles to a standard ignition source, deriving measurement values for afterflame time, afterglow time, and char length.

5.2 The vertical flame resistance, as determined by this test method, only relates to a specified flame exposure and application time.

5.3 This test method maintains the specimen in a static, draft-free, vertical position and does not involve movement except that resulting from the exposure.

5.4 Test Method D6413 has been adopted from Federal Test Standard No. 191A method 5903.1, which has been used for many years in acceptance testing. The between-laboratory precision of this test method has not been established. Refer to Section 14 for single-laboratory precision.

5.4.1 If there are differences or practical significance between reported test results for two laboratories (or more), comparative tests should be performed to determine if there is a statistical bias between them, using competent statistical assistance. As a minimum, the test samples used should be as homogeneous as possible, that are drawn from the material from which the disparate test results are obtained, and that are assigned randomly in equal numbers to each laboratory for testing. Other materials with established test values may be used for this purpose. The test results from the two laboratories should be compared using a statistical test for unpaired data, at a probability level chosen prior to the testing series. If a bias is found, either its cause must be found and corrected, or future test results must be adjusted in consideration on the known bias.