ASTM D6413/D6413M

Standard Test Method Flame Resistance of Textiles (Vertical Test)

ASTM D6413/D6413M is the defining test method for compliance with OSHA 1910.269 and one of the most commonly used tests on flame resistant fabrics. Adopted from Federal Test Standard No. 191A, method 5903.1, the vertical flame test has been used for many years.

  • The purpose of this test is to determine whether a fabric will continue to burn after the source of ignition is removed.
  • A 12” specimen of fabric is suspended in an enclosed chamber (secured on three sides).  The cut edge of the fabric on the bottom is exposed to a controlled methane flame for 12 seconds.
  • After exposure to the flame, afterflame, afterglow, and char length are measured.  Five tests are performed and the results are averaged and reported as the test result.
  • ASTM D6413/D6413M is used to determine a pass/fail criteria for ASTM F1506, which requires a maximum char length of 6 inches.
  • Note: ASTM F1506 requires a maximum char length of 6 inches under this test method, whereas NFPA 2112 requires a maximum of 4 inches.  A 6-inch char length is more universally accepted as the maximum.  Char length of FR fabrics does NOT correlate to thermal protective performance in the manikin test. As long as the fabric sample does not ignite and continue to burn (called BEL for Burn Entire Length) char lengths at or below 6” are not meaningful predictorsof thermal protective performance of the fabric in flash fire. In other words, some fabrics with relatively low char lengths have significantly higher body burn percentages in the manikin test than other fabrics with relatively higher char lengths. We do not recommend inclusion of char length in specifications for this reason.

The standard can be purchased and downloaded from the ASTM website at