Utility workers can be exposed to an acute flammability hazard when they are working close to an arcing fault or flashover from electrical equipment or power lines. In the past, it has not been possible to recommend the type of protective clothing that should be worn in these circumstances because no laboratory test method has been available to measure the thermal protective performance (TPP) of fabrics and other laminae against exposure to a high intensity, infrared dominant, radiant energy source similar to that emitted from electrical flashovers. The study describes the use of a recently developed Flash Tester, which, by generating a controlled electrical discharge across welding electrodes, produces radiant flux densities in the 40 to 600 kW/m2 (1 to 15 cals/cm2/s) range. By exposing fabric layers equivalent to various clothing assemblies worn by utility linesmen and a range of 32 flame-retardant (FR) fabrics as single- and multiple-layer specimens, it has been shown that those parts of the body covered by only one fabric layer are exposed to the highest risk of burn injury, whereas for those covered with six or more layers, the risk of burn injury is negligible. The use of single-layer fabrics containing FR fibers or FR finishes provide some additional protection, particularly those with a high mass per unit area (fabric weight), while the use of thicker or lighter colored fabrics does not appear to influence the TPP ratings. More protection is obtained by using two or more fabric layers. However, two layers appear to be effective only when both layers contain fabrics that do not fuse together. Because of strong interactions between fabrics in a multiple-layer assembly, it is not possible to predict the TPP of combined layers worn together from tests of the individual layers.