IFR = Inherently Flame Retardant = Fibers used in making these fabrics will not sustain a flame. These properties are not affected by dampness, water or time.FR = Flame Retardant = Chemically Treated. The effectiveness of the application of a flame retardant chemical, may deteriorate with time and/or when exposed to damp or wet conditions. Since most flame retardants are salt based, they may also leave a white stain after having been wet.SE = Self Extinguishing = The fabric will not sustain a flame without a flame from another source being present. Most Self Extinguishing fabrics will melt when submitted to a flame. This liquid remains hot enough to cause extremely serious burns, long after the flame has extinguished! NFR = Not Flame Retardant. Fabrics are not treated with any flame retardant chemicals and are to be used with extreme caution in the potentially dangerous environment of a motion picture, broadcast, video or still photographic set.