Fire Safety and Technology Editorial
Fire Testing of Textiles
I was recently asked for some clarification on fire testing of textiles.
In the US, fire and life safety codes have requirements for testing of curtain and drapes in accordance with NFPA 701. Those codes and building codes have requirements for testing of textile wall coverings and they reference three different tests: ASTM E 84, NFPA 265 and NFPA 286. Floor coverings, particularly carpets and other textile floor coverings, are tested in accordance with ASTM D 2859 (or its CPSC equivalent, 16 CFR 1630, Standard for the Surface Flammability of Carpets and Rugs) and in accordance with ASTM E 648 (equivalent to NFPA 253, flooring radiant panel). US apparel flammability is regulated by a CPSC standard, 16 CFR 1610, Standard for the Flammability of Clothing Textiles (equivalent to ASTM D 1230) and children’s sleepwear flammability is regulated by another pair of CPSC standards, 16 CFR 1615, Standard for the Flammability of Children's Sleepwear: Sizes 0 Through 6x, and 16 CFR 1616 Standard for the Flammability of Children's Sleepwear: Sizes 7 Through 14 (equivalent to ASTM D 6545). The blanket industry developed a mild voluntary fire standard, which became ASTM D 4151, and the Federal Aviation Administration has long had a special flammability test for blankets, which is in the FAA Aircraft Materials Fire Test Handbook, Chapter 18, “Recommended Procedure for the 4-Ply Horizontal Flammability Test for Aircraft Blankets”. Military uniforms are normally tested using ASTM D 6413, “Standard Test Method for Flame Resistance of Textiles (Vertical Test)”. On top of all of that, textile manufacturers often test their fabrics to the “small-scale NFPA 701” test or to the ASTM E 84 Steiner tunnel test for the fabric alone. Moreover, NFPA 705 is a recommended practice for a “field test” for textiles, using a match. This is all very confusing! I will try to explain some of it.
NFPA 701: it is an ancient test, first developed in 1938, for vertical fire testing of textiles, principally curtains and drapes. It measures flame propagation based on weight loss or char length. It originally contained three tests but one of them was taken out to create the recommended practice in NFPA 705 (a match test intended to confirm whether an existing curtain or drape is particularly dangerous; if a match causes a big fire, the material is a problem). Following the 1989 edition, the “small-scale test” was eliminated because it was shown that it did not adequately predict what happened in realistic fires; however many manufacturers of textiles continue testing to it and publish their results in data sheets; they often still refer to the results as NFPA 701 test results. All NFPA 701 editions since then consist of two tests: Test 1 (some times known as the phone booth test, based on weight loss) applies to fabrics with areal density not greater than 700 g/m2 (21 oz/yd2) and Test 2 (which is quite large scale with test specimens 125 mm x 1200 mm, ca. 5 in. x 47 in., based on char length) applies to fabrics with areal density greater than 700 g/m2 (21 oz/yd2) as well as to multi-layered fabrics and to vinyl-coated fabric blackout linings.
The NFPA 701 tests should not be used for fabrics that are adhered or glued to a substrate or in any other way attached to a backing because the results would be misleading (particularly due to the effect of the adhesive and the heat sink or heat contribution from the substrate). However, this is done often, incorrectly. The NFPA 701 tests are often used as a way of characterizing the flammability of textiles used for various applications; for example it is not unheard of for manufacturers of furniture or mattresses to specify that the fabrics to be used for the covers must have passed the NFPA 701 test.
In the US all wall and ceiling interior finish is normally tested for regulation by the Steiner tunnel test (ASTM E 84), which gives results in terms of flame spread index and smoke developed index. However, it was shown by Professor Brady Williamson many years ago that the ASTM E 84 test gave misleading results for textile wall coverings (ASTM E 84 Class A (best class) textile wall coverings can lead to room flashover) and therefore codes will require the added use of sprinklers unless the textile wall covering system is fire tested using a room corner test. In the US there are two room corner tests, which assess heat release, smoke release and the probability of flashover: NFPA 286 applies to all materials and has an input flame that exposes walls and ceiling, while NFPA 265 applies to textile and expanded vinyl wall coverings (and not ceiling coverings) only, and uses a less severe ignition source. When wall or ceiling coverings (including textile ones) are tested using ASTM E 84 the entire system (with the adhesive and the substrate) is tested using a specific mounting practice: ASTM E 2404.
Some manufacturers want to test their textile wall covering in isolation in the Steiner tunnel. The appendix of ASTM E 84 provides some guidance for that. It is essential to remember, though, that this testing is intended for research and development only. It is inappropriate to present to regulators or to specifiers because these tests do not consider the effects of the other components in the system. The same appendix section of ASTM E 84 is also used as the excuse by some manufacturers to test carpets in the Steiner tunnel, although it has been shown that carpets do not generate adequate results in the Steiner tunnel test.
Carpets and rugs are required to be tested in accordance with the methenamine pill test (ASTM D 2859) before sales into the US. Floor coverings applications (principally those that are textile-based) in high risk are required to comply with a certain minimum critical radiant flux in the flooring radiant panel, which could be either NFPA 253 or ASTM E 648 (they are equivalent). In this test what is assessed is how small an incident heat flux (in W/cm2) will still spread a flame. The thermal insult comes from a radiant panel at a 30 degree angle which exposes the floor covering to a heat flux ranging from 0.1 W/cm2 (on one end) to nominally 1.0 W/cm2 (on the other end).
All other textile fire tests are small scale tests with small ignition sources and are very specific for some materials. Two of the tests (ASTM D 1230, for wearing apparel, and ASTM D 4151, for mattresses) use a hypodermic needle as the ignition source (with butane for ASTM D 1230 and methane for ASTM D 4151) and they are very mild (tissue paper passes ASTM D 1230). The other tests use small gas (Bunsen-type) burners and are significantly more realistic.
Marcelo M. Hirschler
