Project Aquarius .10. Effects of work, weather, and fire on the energy expenditure, strain, and productivity of men suppressing wildland fires

Four crews of male firefighters were studied while they attempted to suppress well-developed experimental bushfires of intensities commonly faced by hand-tool crews, and also while they built fireline in the same way without fire, during three summers in Australian eucalypt forests. Multiple-regression analyses of their responses showed that they maintained their deep body temperature and heart rate at constant and sustainable levels over a wide range of work duration and intensity, and of heat from weather and fire that frequently exceeded the limits recommended in current heat-stress guidelines. Energy expenditure declined slightly with warmer weather and fire although not with rake duration. Productivity was unchanged by warmer weather but declined slightly with rake duration and with fire. The findings confirm the effectiveness of the firefighters' work practices that allowed them to set their own pace, and of their light, well ventilated clothing that permitted unrestricted evaporation of sweat.