Head cooling is desirable but not essential for preventing heat strain in pilots

Liquid-cooled garments (LCGs) are being considered for reducing heat strain in pilots. While head cooling has been shown to be thermally efficient and subjectively desirable, it is technically difficult to achieve. This laboratory study was carried out to see if head cooling in addition to torso cooling is a necessity. Six male subjects wore a cooling vest and cap under summer flight clothing on three occasions in a climatic chamber set at Tdb = 42 degrees C, Twb = 32 degrees C (RH = 50%), Tg = 52 degrees C at head position, WBGT = 35 degrees C. Cooling conditions were: control (CTRL), no fluid circulation; condition VEST, only torso cooling; condition HEAD, both torso and head cooling. Cooling fluid was circulated from a reservoir maintained at 10 degrees C. Subjective thermal comfort assessments confirmed the desirability of head cooling, but performance measurements and physiological measurements of thermal strain showed no statistically significant differences between conditions VEST and HEAD. It was concluded that head cooling is desirable but not essential.