Insensible weight loss of clothed resting subjects in comfort zone temperatures

¹ Biothermal Section, Biomedical Laboratory, 6570th Aerospace Medical Research Laboratories, Wright-Patterson Air Force Base, Ohio

Insensible weight loss rates of clothed sitting subjects exposed to various temperatures in the range (22–32 C) were measured with a precision system in which weight losses are balanced automatically, displayed on a digital voltmeter, and printed on paper as a function of time. Accuracy of the scale is ± 5 g. Thirty-nine experiments were conducted on ten male subjects wearing light clothing (0.9 clo), exposed 2 hr at 22, 23.9, 26.7, 29.4, and 32.2 C and constant (10 mm Hg) ambient water-vapor pressure. First hour was for equilibration. Mean skin and body temperatures were measured with 17 thermistors and rectal thermistor, respectively. At ambient temperatures 22–26.7 C insensible loss rate increased slightly (21–26.5 g/m² hr). From 26.7 to 32.2 C, however, increase is marked (26.5–64 g/m² hr) with an abrupt rate increase at 26.7 C ambient and at a mean skin temperature of 34.6 C. Importance of ambient air temperature as a control factor in total water loss of subjects in closed space systems is shown.

Submitted on April 4, 1963