PROJECT-AQUARIUS .7. PHYSIOLOGICAL AND SUBJECTIVE RESPONSES OF MEN SUPPRESSING WILDLAND FIRES

The responses of four crews of 7-8 men were measured while they attemp ted to suppress well-developed experimental bushfires of intensities c ommonly faced by hand-tool crews, and also while they built fireline i n the same way without fire, during three summers in dry eucalypt fore sts of SW and SE Australia. Average values were sweat rate 1,144 g h(- 1), heart rate (HR) 152 beats min(-1), and rectal temperature (Tre) 38 .2 degrees C. Changes in the average temperatures of clothed and unclo thed skin were negligible, indicating efficient evaporation of sweat. Firefighters considered the work 'somewhat hard', and felt 'just too w arm' and 'wet' with sweat. By contrast, the responses of the scientifi c observers, doing less strenuous work in the same environment, were m inimal: sweat rate 292 g h(-1), HR 80 beats min(-1), and Tre 37.6 degr ees C. Firefighters' responses were mainly due to exertion rather than fire, confirming an identical finding from measurements of their ener gy expenditure and thermal environment. Differences between attacks wi th and without fire were small in both groups (HR 8-9 beats min(-1), T re 0.1-0.2 degrees C) except for sweat rate (firefighters 401 g h(-1), observers 181 g h(-1)), and were usually present before the attacks b egan. All responses were highly consistent over the four crews, three summers, and two regions. The above findings show that the firefighter s worked within their capacity and paced themselves to sustain their o wn preferred equilibrium levels of strain. They also demonstrate the e ffectiveness of the firefighters' clothing and work practices.