Abstract

A comparison has been made between humid and dry air for ventilating a heat-protective jacket. At sensible cooling capacities of 4·5 kcal./min. and above, humid and dry air provided equal protection. At sensible cooling capacities of 4 kcal./min. and above, the subject achieved thermal equilibrium within 65 min. with both humid and dry air, but below this value humid ventilating air is associated with elevated sweat rates and a failure to achieve thermal equilibrium within 65 minutes.