The vertical flame resistance of a test specimen is measured according to ASTM D 6413 Standard Test Method for Flame Resistance of Textiles.
Under controlled laboratory conditions, material response to heat and flame is measured and described. A test specimen is positioned vertically above a controlled flame and exposed for a specified period of time. Following exposure, the flame source is removed. Measurements are made on the length of time that the specimen continues to flame and the time afterglow continues after the flame source has been removed. Char length, or visible damage to the test specimen after application of a specified tearing force, is determined. Notations on observations of melting and dripping are also recorded.