the united states army aeromedical research laboratory (usaarl) porcine cutaneous bioassay technique was used to determine what mitigating effect four thermally protective flight suit fabrics would have on fire-induced skin damage. the fabrics were 4.8 oz. twill weave nomex aramide, 4.5 oz. stabilized twill weave polybenzimidazole, a 4.8 oz. plain weave experimental high temperature polymer, and 4.8 oz. plain weave nomex aramide. each fabric sample was assayed 20 times in each of four configurations: as a single layer in contact with the skin; as a single layer with a 6.35 mm (one-fourth inch) air gap between fabric and skin; in conjunction with a cotton t-shirt with no air gaps; and, finally, in conjunction with a t-shirt with 6.35 mm air gap between t-shirt and fabric. bare skin was used as a control. a jp-4 fueled furnace was used as a thermal source and was adjusted to deliver a mean heat flux of 3.07 sq cm sec. the duration of exposure was five seconds. four hundred burn sites were graded using clinical observation and microscopic technique