All fabrics can catch on fire but some have a tendency to catch fire more quickly than others. Clothing with high concentrations of rayon can become combustible quickly. Untreated natural fibers such as cotton, silk and linen can burn more easily than wool, which is difficult to ignite and burns with a low intensity flame.
The purpose of flammable regulations is to keep highly flammable clothing out of the commerce market. To test clothing for flammability, the Consumer Product Safety Commission classifies fabrics into three classes of flammability, which are based on the speed in which they burn during testing.
Clothing is deemed unsuitable for commerce if it’s labeled as Class 3, which means the fabric in the textiles burns too rapidly and the fire is too intense. Testing is performed on clothing both before and after it is washed using the care instructions mandated by the Care Labeling Rule.
Years of flammability testing reveal that fabrics that consistently pass testing are labeled as safe:
Class 1 textiles. This clothing has a flame spread time of 3.5 seconds or more for plain surface fabrics.
Class 1 textiles. This clothing has a flame spread time of 3.5 seconds or more for plain surface fabrics.
Class 2 textiles, which consist of raised fiber surfaces, have a flame spread time from four to seven seconds. Class 2 textiles are labeled “intermediate flammability.”
Class 3 textiles “exhibit rapid and intense burning,” are labeled as “dangerously flammable” and cannot be sold in the U.S. as clothing. Class 3 textile fabrics considered to be dangerous include untreated sheer rayon or silk, reverse fleece, rayon chenille, Sherpa of cotton, cotton blend and certain cotton terry cloth.