The thermal aspect of comfort, as defined under A~HRAE COMFORT STANDARD 55-74 (1), is "that state of mind which express~s satisfaction with the thermal environment." By this definition, comfort and discomfort sensations are inherently subjective and fall into the category of avoidance of discomfort due to excessive cold or warmth. Much of the classic research by· heating and ventilating engineers ha.s been done with the goal that a constant level of room temperature and humidity was desirable in order to prociuce this absence of discomfort. It is becoming increasingly apparent that factors affecting thermal comfort and sensations, such as changes in activity and clothing habits, room temperature, air movement, and humidity are diverse, especially in large indoor structures, and it is not possible to meet everyone's state of thermal comfort by rigorous room control.

Studies by Wyon et al. (2), in which subjects were exposed to temperature variations, indicate that individuals actually prefer temperature swings about the optimum. Sprague and McNall (3} reported that sedentary individuals relate thermal sensation to dry-bulb temperatures more closely and consistently if the temperature rates are higher than 0.125 02/min, [determined by the product of the peak amplitude and average rate of air temperature variation]. Earlier work by Gagge et al. (4} showed that transient thermal · stimuli produced changes in discomfort estimates prior to changes in physiological responses. Keeping these studies in mind 1 any small environmental fluctuations in indoor structures about an optimum ambient temperature would be judgedin advance of wide average skin or internal body temperature changes and remedied by an appropriate behavioral change (e.g., adding a coat or removing it) or room thermostat adjustments.