Document zQaoVdqGEx4XkoK0jXvbowMk7

American Society of Heating and Ventilating Engineers Guide, 1930 There are three principal factors affecting loss of body heat: (1) tem perature; (2) humidity; (3) air motion. As the temperature of the air and surrounding objects rises, the loss of heat by convection and radiation decreases. When the air temperature Chapter 3--Standards of Ventilation librium by making available more perspiration, resulting in a greater heat loss by evaporation. From the foregoing, it is concluded that there must necessarily exist certain combinations of temperatures and humidities, which produce the same total body heat loss by radiation, convection, and evaporation, reaches that of the body, the loss by radiation and convection ceases. Finally, as the air temperature exceeds that of the body, heat is trans ferred from the air to the body. As the temperature of the air rises and heat loss by radiation and con vection decreases, the body endeavors to maintain temperature equi- 90 Fig. 2. 70 Dry bulb temperature Psychrometric Chart with Effective Temperature Lines for 100 ft. Air Velocity. (Shaded Area Indicates the Comfort Zone) and, therefore, the same feeling of comfort or discomfort. Lines passing through such air conditions plotted as a psychrometric chart may be called equal comfort lines. The fact is further substantiated by the general experience of heating engineers in observing that the lower the humidity the higher the dry-bulb temperature required for the same degree of comfort. 91