Project Aquarius 5. Activity Distribution, Energy Expenditure, and Productivity of Men Suppressing Free-Running Wildland Fires With Hand Tools

Abstract

Timed-activity studies were made of four crews while they attempted to suppress well-developed experimental bushfires of intensities commonly faced by handtool crews, and also while they built fireline in the same way without fire, during three summers in Australian eucalypt forests. Fireline construction with rakehoes (including step up) occupied, on average, 63% of the crew's time. Firefighters raked for 38 seconds followed by 10 seconds of step up, thus obtaining frequent brief rests for the arm muscles involved in raking. Energy expenditure (EE) of all fire-suppression activities averaged 516 W, equivalent to a relative work load (RWL) of 45% of the men's maximum work capacity. Pulmonary ventilation averaged 55 (range 38-83) 1 min-1 during raking and 40 (range 23-73) 1 min-1 during all activities. Each firefighter built 1.90 m2 of fireline per minute of raking, and 1.21 m2 min-1 over the whole period of the attack. Each hour the six men engaged in fireline construction built and held 436 m2, i.e. 512 metres of fireline 0.85 metres wide. Individuals consistently differed twofold in their self-chosen levels of raking EE and RWL and threefold in productivity and efficiency (productivity per unit EE), whereas average raking EE did not differ between crews, nor between attacks with and without fire. We conclude that wildland firefighters pace themselves at their own preferred and sustainable work rates.