Comfort and thermal sensations and associated physiological responses at various ambient temperatures

Sensory estimates of comfort and thermal sensation for resting-sitting unclothed subjects have been compared with the associated physiological responses for the range of ambient temperatures (12°–48°C) under steady-state and transient conditions. For steady exposure to cold and warm environments, thermal comfort and neutral temperature sensations lie in the range for physiological thermal neutrality (28°–30°C), in which there is no physiological temperature regulatory effort. Discomfort increases more rapidly below 28°C than above 30°C, while thermal sensation for both heat and cold increases rapidly each side of neutral. Discomfort correlates best with lowering average skin temperature toward cold environments and with increased sweating toward hot environments. In general, discomfort is associated with a change of average body temperature from 36.5°C. The same conclusion follows for transient changes when the subject goes from comfortable to uncomfortable, neutral to cold, and neutral to warm. When these transients are reversed (i.e., cold to neutral, hot to neutral), the sensations of comfort and temperature “lead” the body temperature changes and are thus “anticipatory.” This hysteresis effect is most striking in the cold and less so for warmth. For transients from cold to warm, the rate of rise of skin temperature causes a sensation that compensates for and predominates over the sensation of discomfort caused by a low skin temperature itself. Finally, thermal discomfort is an excellent stimulus for behavioral activity by man. As a sensation, it gives man both an early and anticipatory drive for conscious action that may effect changes in his body's microclimate rather than having him depend on natural but short-term means of thermal protection—sweating, vasodilation, vasoconstriction and shivering.