Document By3aJ4axgxrBv4KkjVg7p30Yo

American Society of Heating and Ventilating Engineers. Guide, 1934 120--1 -tzo FlG' h Effective Temperature Chart Showing Normal Scale of Effective Temperature. Applicable, to Inhabitants of the United States Under Following Conditions: c-- 24 Chapter 2--Ventilation and Air Conditioning Standards pneumonia death rate is associated with dust, extreme heat, exposure to cold, and to sudden changes in temperature. ACCLIMATIZATION Acclimatization and the factor of psychology are two important in fluences in air conditioning which cannot be ignored. The first is man's ability to adapt himself to changes in air conditions; the second is an intangible matter of habit and suggestion. Some persons regard the unnecessary endurance of cold as a virtue. They believe that the human organism can adapt itself to a wide range of air conditions with no apparent discomfort or injury to health. In the light of the present knowledge of air conditioning these views are not justified. Acclimatization to extreme conditions involves a strain upon the heat regulating system and it interferes with the normal physiologic functions of the human body. Thousands of years in the heat of Africa do not seem to have acclimatized the Negro to a temperature averaging 80 F. The same holds true of northern races with respect to cold, although the effects are mitigated by artificial control. All this seems to indicate that adaptation to a climate averaging between 60 and 80 F is a very primitive trait9. In certain individuals the psychologic factor is more powerful than acclimatization. A fresh air fiend may suffer in a room with windows closed regardless of the quality of the air. As a matter of fact, instances are known in which paid subjects refused to stay in a windowless but properly conditioned experimental chamber because the atmosphere felt suffocating to them upon entering the room. SENSATIONS OF WARMTH AND COMFORT Temperature, humidity and air motion taken together determine the feeling of warmth and influence the elimination of body heat. In other words, the temperature sensations of the human body depend not only on the temperature of the surrounding air as registered by a dry-bulb thermometer, but also upon the temperature indicated by a wet-bulb thermometer. Dry air at a relatively high temperature may feel cooler than air of considerably lower temperature with a high moisture content. Air motion makes any moderate condition feel cooler. On the other hand, in cold environments an increase in humidity produces a cooler sensation. The dividing line at which humidity has no effect upon comfort varies with the air velocity and is about 46 F (drybulb) for still air and about 51, 56 and 59 F for air velocities of 100, 300 and 500 fpm, respectively. Thermo-Equivalent Conditions Combinations of temperature, humidity and air movement which pro duce the same feeling of warmth are called thermo-equivalent conditions. Elaborate experiments made by the A.S.H.V.E. Research-Laboratory Civilization and Climate, by Ellsworth Huntington, Yale University Press, 1924. 25