16 C.F.R. § 1611.34
In determining whether an article of wearing apparel is so highly flammable as to be dangerous when worn by individuals, only the uncovered or exposed part of such article of wearing apparel shall be tested according to the applicable procedures set forth in section 4(a) of the act.
Note: If the outer layer of plastic film or plastic-coated fabric of a multilayer fabric separates readily from the other layers, the outer layer shall be tested under part 1611-Standard for the Flammability of Vinyl Plastic Film. If the outer layer adheres to all or a portion of one or more layers of the underlying fabric, the multilayered fabric may be tested under either part 1611 or Part 1610-Standard for the Flammability of Clothing Textiles. However, if the conditioning procedures required by § 1610.4(f) of the Standard for the Flammability of Cloth Textiles would damage or alter the physical characteristics of the film or coating, the uncovered or exposed layer shall be tested in accordance with part 1611.
Plastic film or plastic-coated fabric used, or intended for use, as the outer layer of disposable diapers is exempt from the requirements of the standard, provided that a sample taken from a full thickness of the assembled article passes the test in the standard (part 1610 or part 1611) otherwise applicable to the outer fabric or film when the flame is applied to the exposed or uncovered surface. See §§ 1610.36(f) and 1611.36(f) .
16 C.F.R. §1611.34