The physiological effects of clothing comprising seven different material systems with a range of total heat loss values from 96.5 to 439 W/m2 were measured. Two different 1-hour work protocols were established for simulating both a vehicle extrication activity and the fire ground operations of a ladder company. Each work protocol used a series of different physical tasks involving varying levels of work but characterized overall to be in the moderate to high work levels. The study employed seven fire fighter test subjects who were instrumented for continuous, real-time monitoring of core temperature, skin temperature, and heart rate through a telemetry system. Data were collected every nine seconds for each of the 98 separate evaluations. The test subject nude weight loss and clothing system weight gain were also measured. The participating fire fighters rated the individual clothing systems subjectively for different characteristics during the work period.
Both physiological and subjective data from this test were analyzed with respect to garment and material system characteristics to determine if any relationship existed. For both work protocols, differences in physiological responses were consistent with the total heat loss values of the material systems evaluated. For example, regression analyses showed ith greater than 95% that total heat loss can be used to predict core temperature rise, skin temperature rise, nude weight loss, and system weight gain. In addition, total heat loss explained more of the differences in physiological responses than any other independent variable studied. In the case of subjective responses, this regression also showed that garment weight explained more of the differences between subjective responses than other independent variables.