The heat-ipsulation characteristics of eighteen fire-retardant-treated fabrics; two Nomex fabrics, and a Kynol fabric are examined. Exposure both to flame and to radiation sources is employed. For a low level of radiation exposure, fabric thickness correlates well with protection time. As incident heat flux is increased, other less bvious factors begin to contribute to protection times. Technical considerations to produce effective safety-apparel fabric are summarized.