Document 6bqRZKMzEr7adVoGk4jBMaJdE

210 CHAPTER 12 1948 Guide saturated with moisture. The effective temperature index cannot be measured directly but is determined from dry- and wet-bulb temperatures and air motion observations by reference to an Effective Temperature Chart (see Figs. 8, 9, and 10) or tables. Fig. 8 gives the effective temperature for any combination of dry- aiid wet-bulb temperatures for still air (15 to 25 fpm) conditions. Charts similar to Fig. 8 for air velocities of 300 and 500 fpm have been presented in some of the earlier editions of the Guide. Fig. 9 is another form of Physiological Principles 211 effective temperature chart embodying all three variables; dry-bulb and wet-bulb temperatures, and air velocity. As stated previously, effective temperature is an index of the degree of warmth experienced by the body. An effective temperature line is, there fore, a line defining the various combinations of conditions which will induce like sensations of warmth. It does not necessarily follow that like sensations of comfort will also be experienced along the entire length of an effective temperature line. Some degree of discomfort is likely to be experienced at very high or very low relative humidities, regardless of the effective temperature. It has also been found that the optimum effective temperature varies with the season, and is lower in winter than in summer. A. Clothine: Customary indoor clothing. B. Activity: Sedentary or light n>*u|frworfc C. Hcctint