Fire-retardant fabrics, also known as chemically flame retardant fabrics, are standard fabrics that have been treated with a special flame-retardant coating. They will burn, but at a much slower rate than untreated standard fabrics. Flame retardancy is classified into three groups: flame retardant (FR), inherently flame retardant (IFR), and durably flame retardant (DFR). Flame-resistant fabrics are made up of typically synthetic fibers that resist ignition under prolonged exposure to flame or heat. Because of this construction, they are also sometimes referred to as inherently flame-retardant fabrics. Instead of burning, these fabrics will eventually begin to melt. The degree of inherently flame-resistant fibers within a flame-resistant fabric can vary widely from a few percent of the fibers to a full construction, depending on the manufacturer.