Brake and Bates [13]monitored the deep body core temperatures of 36 industrial workers continuously, and the results indicated that the values regularly exceeded the commonly recommended limits (a temperature of 38.0 °C or an increase of +1 °C) with the average maximum deep body core temperature was 38.3 °C, the maximum temperature rise was 1.4 °C, and the maximum heat storage was 431 kJ. Kalkowsky and Kampmann [14] carried out a study to record the physiological strain of miners. 38 miners were asked to participate during 125 shifts, and the heart rate and rectal temperature were measured continuously.