The federal clothing flammability standard: the 45 degree burn test, three classes and the fabrics that skip it

The clothing flammability standard is 16 CFR part 1610, a federal rule from the Consumer Product Safety Commission. It tests clothing fabric by flame, sorts it into three classes by burn time, and bans only Class 3, rapid and intense burning. It does not require clothes to be flame resistant, and several common fabrics are exempt from testing.

What the standard is for

Section 1610.1(a) states the purpose: "to reduce danger of injury and loss of life by providing, on a national basis, standard methods of testing and rating the flammability of textiles and textile products for clothing use, thereby prohibiting the use of any dangerously flammable clothing textiles." The standard rests on the Flammable Fabrics Act, which Wikipedia reports was signed on June 30, 1953, and was passed in response to reports of rayon viscose fabrics that ignited quickly. Our explainer on what viscose is covers the fiber.

The enforcement hook is in the statute. Under 15 U.S.C. 1192, manufacturing for sale, selling, offering for sale in commerce or importing a fabric or product that fails to conform to an applicable standard is unlawful, and treated as an unfair method of competition and an unfair and deceptive act under the FTC Act.

How the burn test works

The method in sections 1610.3 and 1610.6 is a small, controlled flame test. A specimen of 50 mm by 150 mm, about 2 by 6 inches, is cut from the fabric. It is held in a frame at a 45 degree angle in a draft-proof chamber, and raised-fiber fabrics are brushed first. A standardized flame is applied near the lower end for 1 second. The time for the flame to proceed 127 mm, or 5 inches, up the fabric is recorded. For raised-surface fabrics, testers also note whether the base fabric ignites or fuses.

Every fabric is tested twice: in its original state, and after "refurbishing," which the standard defines as dry cleaning and laundering. Under section 1610.7(a), the final classification is the more severe of the two results. For plain surface fabrics, testers run five specimens in the fastest-burning direction, then add five more in some cases.

Some constructions need special handling, and 1610.6(a)(1) lists them. Fabrics that are flocked overall are treated as raised surface; flock printed fabrics, usually in a pattern, are plain surface. Patterned cut velvet is raised surface. Metallic thread fabrics are plain surface if the base fabric is smooth, with the specimen cut so the flame meets a metallic thread. Embroidery on netting is tested at its most flammable area. The list is described in the text as not all-inclusive.

The three classes

The classes sort fabrics by burn time, with different cutoffs for plain and raised surfaces.

• Class 1, normal flammability: acceptable for clothing. A plain surface fabric needs a burn time of 3.5 seconds or more. A raised surface fabric needs more than 7.0 seconds, or a rapid surface flash that does not ignite or fuse the base fabric.
• Class 2, intermediate flammability: applies only to raised-fiber surfaces and "may be used for clothing." The burn time is 4.0 through 7.0 seconds with the base fabric burning at places other than where the flame was applied.
• Class 3, rapid and intense burning: "dangerously flammable" and not to be used for clothing. A plain fabric lands here if the flame spreads in less than 3.5 seconds. A raised fabric lands here at less than 4.0 seconds with base burning.

So the line for plain fabric is 3.5 seconds over 5 inches. A fabric that burns slower than that is acceptable even if it burns readily, which is why the standard is a floor, not a promise.

What is exempt

Section 1610.1(c) excludes hats that do not cover the neck, face or shoulders, gloves not more than 14 inches long and not part of another garment, footwear that is not hosiery or attached to a garment, and interlining fabrics.

Section 1610.1(d) then exempts certain fabrics from testing to support a guaranty, because years of testing show they pass. These are plain surface fabrics weighing 2.6 ounces per square yard or more, regardless of fiber, and all fabrics, plain or raised, made entirely of acrylic, modacrylic, nylon, olefin, polyester or wool. Other items aren't tested because they can't be: narrow fabrics under 50 mm wide and items such as fringe, feathers, wigs and hula skirts, where a 2 by 6 inch specimen cannot be cut, are not tested.

Raised-surface fabrics get the extra check for a reason the definitions spell out. Section 1610.2 describes surface flash as a rapid burning of the pile fibers and yarns on a raised surface, which may or may not burn through to the base fabric, and the class turns on whether it does.

What it does not cover

Children's sleepwear is handled under separate rules, and our report on why kids' pajamas fit tightly explains them. Part 1610 is about clothing textiles generally. It classifies fabrics and bans the worst, and it does not set a flame-resistance requirement.

Our take

The standard works the way a minimum safety rule should: it is cheap, repeatable, written in plain numbers and tied to a clear prohibition. It is also narrower than its reputation. Nothing here makes a shirt flame resistant, and the exemption for heavier plain fabrics and for polyester, nylon and wool means many fabrics need no burn test to support a guaranty. If a brand claims a garment is flame resistant, ask for the standard and the test report. A pass on part 1610 means only that the fabric is not among the fastest-burning textiles the rule bans.