{"id":1762,"date":"2026-11-04T16:53:35","date_gmt":"2026-11-04T08:53:35","guid":{"rendered":"https:\/\/brt-testing.com\/?p=1762"},"modified":"2026-11-04T16:53:35","modified_gmt":"2026-11-04T08:53:35","slug":"how-to-test-flame-retardant-textiles","status":"publish","type":"post","link":"https:\/\/brt-testing.com\/pt\/how-to-test-flame-retardant-textiles\/","title":{"rendered":"How to Test Flame Retardant Textiles: Ignition, Flame Spread and Clothing Standards"},"content":{"rendered":"

The Short Answer<\/h2>\n

Flame retardant textile testing starts with two questions: what will the fabric be used for, and which market regulates it.<\/strong> Vertical ignition and flame-spread testing to ISO 6940<\/strong> and ISO 6941<\/strong> answers “does it ignite, and how fast does flame climb” 1<\/a>2<\/a>; protective-clothing fabrics then move into the performance chain of ISO 15025<\/strong>, EN ISO 14116<\/strong> and EN ISO 11612<\/strong> 3<\/a>4<\/a>5<\/a>; apparel and drapery in the US use ASTM D6413<\/strong>, ASTM D1230<\/strong>, the 16 CFR 1610<\/strong> apparel rule and NFPA 701<\/strong> 6<\/a>7<\/a>. Everything else \u2014 limiting oxygen index, heat transmission \u2014 is screening or supporting data, not a substitute for the spread-of-flame test your specification names.<\/p>\n

What “Flame Retardant” Means Before Any Test Runs<\/h2>\n

Two fabrics can both be called flame retardant and behave completely differently in a test. A fabric woven from inherently FR fibres (aramid, modacrylic, FR-modified cellulose) carries its protection in the polymer; a fabric finished with a durable or non-durable FR treatment carries it in a coating that laundering can reduce. Testing method cannot tell them apart \u2014 which is exactly why standards define conditioning<\/strong> (number of washes or cleaning cycles before the test) as part of the procedure. A test report that does not state how many cleaning cycles preceded the burn does not answer the buyer’s real question.<\/p>\n

The other variable is construction. ISO 6940 and 6941 apply to single- and multi-component fabrics \u2014 coated, quilted, multilayer and sandwich constructions \u2014 so composite curtain or upholstery systems can be tested as built [1][2]. But a result belongs to the tested construction; relining a curtain or changing the interlayer takes it outside the report.<\/p>\n

A third variable is the direction of exposure. Many fabrics are not symmetric: a coated blackout fabric faces the flame with its coating side or its backing side, and the two states can differ by a wide margin. Standards handle this by defining which face is exposed; procurement documents should do the same, because “tested to ISO 6941” without the exposed face stated leaves the most common dispute in textile fire testing unresolved. Where a specification is silent, laboratories test the face that would face the fire hazard in service, and record that choice in the report.<\/p>\n

Finally, thickness and areal density drive behaviour more than fibre labels do. Two fabrics of the same fibre blend but different weights perform differently under the same small flame, so specification tables that compare fabrics by brand name alone, without areal density, invite false equivalences.<\/p>\n

The Core Vertical Tests: ISO 6940 and ISO 6941<\/h2>\n

Ignition versus flame spread<\/h3>\n

The pair splits one question into two. ISO 6940<\/strong> measures ease of ignition<\/em>: a vertically oriented fabric faces a small defined flame, and the result is the time to ignition (or “no ignition” at the standard exposure) [1]. ISO 6941<\/strong> measures flame spread<\/em>: the time for the flame front to reach reference marks on the vertical specimen, reported as spread times from which a flame-spread index is derived [2]. A fabric can pass one and not the other \u2014 a heavy upholstery weave may resist ignition but, once alight, spread steadily.<\/p>\n

The 2026 editions just replaced two decades-old versions<\/h3>\n

Both documents were reissued in 2026: the 2004 edition of ISO 6940<\/strong> and the 2003 edition of ISO 6941<\/strong> were withdrawn on 13 May 2026<\/strong>, the same day the 2026 editions entered force [1][2]8<\/a>9<\/a>. The current scope language covers the same vertically oriented single- or multi-component fabrics under a small defined flame [1][2]. Two practical consequences follow: laboratories should update their scope statements and report templates to the 2026 designations, and any supplier datasheet still citing ISO 6940:2004 or 6941:2003 is quoting withdrawn documents. (This site tracks such renumbering \u2014 see our note on EN ISO 11925-2, the small-flame test for building products<\/a>, which went through its own edition change in 2026.)<\/p>\n

What each of the pair fixes, in broad terms:<\/p>\n

\n\n\n\n\n<\/colgroup>\n\n\n\n\n\n\n\n\n
Aspect<\/th>\nISO 6940:2026<\/th>\nISO 6941:2026<\/th>\n<\/tr>\n<\/thead>\n
Question answered<\/td>\nDoes the fabric ignite under the defined flame?<\/td>\nHow far and fast does flame spread once burning?<\/td>\n<\/tr>\n
Specimen orientation<\/td>\nVertical [1]<\/td>\nVertical [2]<\/td>\n<\/tr>\n
Fabric types covered<\/td>\nSingle- and multi-component: coated, quilted, multilayer, sandwich [1]<\/td>\nSame families [2]<\/td>\n<\/tr>\n
Headline result<\/td>\nTime to ignition (or no ignition) [1]<\/td>\nFlame spread times to reference marks [2]<\/td>\n<\/tr>\n
Typical role in a spec<\/td>\nIgnition-resistance requirement<\/td>\nSpread-resistance requirement<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

The two share apparatus in practice \u2014 the same vertical test cabinet, ignition flame and conditioning regime serve both, which is why a single textile vertical flammability tester covers the pair. What changes between them is the observation protocol and the reporting.<\/p>\n

\"FCZ-50<\/a>
FCZ-50 textile vertical flammability tester \u2014 the cabinet family behind ISO 6940, ISO 6941 and ISO 15025 work; see the product page.<\/figcaption><\/figure>\n

The Protective Clothing Chain<\/h2>\n

Workwear and firefighter-adjacent garments are not specified by ignition time alone; they use layered performance standards:<\/p>\n