A series of field trials was undertaken to evaluate the thermal properties of five different personal protective ensembles, under more realistic experimental conditions. This project was designed to address the following applied questions, which could assist in the selection of suitable ensembles for the New South Wales Fire Brigades: (a) Are there between-ensemble differences in the storage of metabolically-produced heat? (b) Are there between-ensemble differences in physiological strain during real-task simulations? (c) Are there between-ensemble differences in the penetration of external heat? These field trials included two simulated fire exposures (Hot Fire Cell and Flashover Simulator), during which, from a physiological perspective, we observed remarkable clothing and local tissue temperature changes (Taylor et al., 2001). Herein we describe some of those observations.