Flame resistance refers to a fabric's ability to resist burning.
The appropriate flammability test is dictated by the intended end use for the fabric. The
two testing methods most commonly used to measure flame resistance are the Tunnel Test (ASTM E-84) and the Vertical Flame Test (used by California Bulletin 117 and NFPA 701).
In the Tunnel
Test, the fabric to be evaluated is clamped (unadhered method) or glued (adhered method) to a substrate. The substrate is placed on the ceiling of the test chamber and ignited by a flame from
below. The fabric sample is then evaluated for the density of the smoke formed, the amount of fuel contributed and the extent of the flame spread. Based on these factors, a rating is established.
In the Vertical Flame Test, the fabric to be evaluated is mounted in a vertical holder and exposed to an open flame for a specified amount of time. Once the flame is removed, the after flame
and char length of the test sample are measured against various code standards to establish a classification.
The NFPA 701 utilizes the Vertical Test but unlike California Bulletin 117, the
test is conducted in "oven dry" conditions, meaning the fabric to be tested is heated and thoroughly dried out prior to testing. The test then proceeds under the standards described
above and a classification is established.