THE RADIATION OF HEAT FROM THE HUMAN BODY

Abstract

I. An instrument was developed for the accurate measurement of surface temp, and body radiation. The device is rugged, portable, easily manipulated, and determines with one reading both the surface temp. and the radiation. The instrument has an accuracy of [plus or minus]0.1[degree] C or [plus or minus]0.1 X 10-4 small calories of heat radiated per sec. per cm2. The device is discussed from a theoretical standpoint to show that its measurements are accurate in absolute value.[long dash]II. Tests which were made of several types of surface thermometers revealed (1) "calibration errors" which arise from the fact that the thermometers are calibrated completely submerged in a liquid of known temp. and not to measure the temp. of a surface with which they are partially in contact; (2) errors due to poor contact of thermometer with the skin, changes in the heat elimination, from the vascular bed, etc.; (3) "manipulation errors" which arise from the fact that the thermal equilibrium established between the thermometer and the skin surface depends on a large number of experimental factors, i.e., pressure with which the thermometer is placed against the skin, room temp., skin moisture, etc. The first 2 sources are systematic. Tests show that, eliminating manipulation errors as far as possible, the relative accuracy of the usual contact skin thermometer is [plus or minus] 0.5[degree] and the absolute accuracy [plus or minus] 1.0[degree] C. The radiometric method is suggested as the simplest and most accurate method for obtaining skin temp.[long dash]III. Additional evidence has been collected which supports the conclusion of Cobet and Branmigk concerning the emissivity of the skin for infra-red light. The value of the emissivity is put at unity with a possible error of 1%.