Human experience of thermal climate is determined by a number of factors in the physical environment. It is affected by the ordinary air temperature (T), the temperature of the surrounding surfaces (Tg: black globe temperature, related to radiant temperature), air humidity (RH, %), and air movement (V, ms-1). Other important factors include activity level and clothing. There are also small differences due to gender, race, and age, but these factors are of lesser importance. The metabolic processes of the body produce warmth; increasing the workload increases heat production. Heat production as a function of activity, clothing, and air speed is given in Table 7.1. Control room work with a low loading gives a heat production in the body of 100 to 130 W, and 160 to 170 W at high loads.