Document jyoZXRM5gKXD0Yp7mZ7OJE3yZ

64 Chapter 2 1945 Guide the ATS.H.V.E.ResearchLaboratory^and-at theJohn-B. Pierce Labora-_ lory of Hygiene?6 give data on the effect of air movement on heat dissipa tion for normally clothed, standing and seated subjects, and for lightly clothed and semi-reclining subjects, respectively. Fig. 9, resulting from A.S.H.V.E. research, shows the increase in dryTmlb and wet-bulb tem-' peratures for the same effective temperature with air velocities ranging., from 20 to 700 fpm. Air velocities may be used for effective cooling; however, great care must be exercised to avoid drafts due to uneven cooling of the body surface. During the heating season air velocities in excess of 25 to 30 fpm usually give undesirable effects. With summer cooling and air con ditioning higher velocities up to 40 or 50 fpm, if properly controlled, seem to give satisfactory conditions free from sensation of draft, while with higher ambient temperatures even higher air velocities may be used. In this connection it may be emphasized that drafts are interpreted61 as local sensations of excessive coolness, and that even while very high air movement in relatively warm air increases the rate of heat loss from local parts of the body, it may improve the comfort of the occupant, so long as that part of his body surface is not excessively cooled. THE FOUR VITAL FACTORS. _______ ____ From the preceding discussion it is clear that>thermal environment cannot properly be adjusted to the requirements of human health and comfort without control of all the four basic factors: 1. Air temperature (free from radiation effects). 2. Air movement. 3. Humidity. 4. Mean radiant temperature of surrounding surfaces. According to the recommendations of the Sub-Committee on the Hygiene of Environmental Conditions in the Dwelling58, it is of great importance in all research studies to make an accurate record of each of the four independent factors governing bodily heat exchanges, tempera ture, movement and humidity of the air, and mean radiant temperature of the surrounding surfaces. For this purpose the committee suggested in the interest of comparability the use of the following four types of instruments or others yielding similar data: 1. Silvered dry-bulb thermometers or hair-pin thermometers (Bargeboer). 2. Silvered dry Kata thermometers or the hot-wire anemometer. 3. Psychrometer, wet- and dry-bulb, whirling or ventilated. 4. Globe thermometer (Vernon) or the dry resultant thermometer (Missenard). In this country, the shielded thermometer, or a very fine wire .thermo couple, has been found more convenient for determining the true dry- "A.S.H.V.E. Research Report No. 691--Cooling Effects on Human Beings Produced by Various Air Velocities, by F. C. Houghten and C. P. Yaglou (A.S.H.V.E. Transactions. Vol. 30. 1924. p. 193). A.S.H.V.E. Research Report No. 717--Effective Temperature with Clothing, by C. P. Yaglou and W. E. Miller (A.S.H.V.E. Transactions. Vol. 31. 192S. d. 89). A.S.H.V.E. Research Report No. MO--Air Motion. High Temperatures and Various Humidities-Reactions on Human Beings, by W. J. McConnell. F. C. Houghten and C. P. Yaglou (A.S.H.V.E. Transactions, Vol. 30. 1924, p. 167). A.S.H.V.E. Research Report No. 718--Work Tests Conducted in Atmospheres of High Temperatures and Various Humidities in Still and Moving Air, by W. J. McConnell and C. P. Yaglou (A.S.H.V.E. Transactions, Vol. 31. 1925, p. 101). The Influence of Air Movement on Heat Losses for the Clothed Human Body, by C.-E. A. Winslow, A. P. Gagge and L. P. Herrington (American Journal of Physiology, October, 1939, VoL 127, p. 505). VA-S.H.V.E. Research Report No. 1086--Draft Temperatures and Velocities in Relation to Skin Temperature and Feeling of Warmth, by F. C. Houghten. Carl Gutberlet and Edward Witkowski (A.S.H. V.E. Transactions, Vol. 44, 1938, p. 289). Housing Commission of the League of Nations, adopted at Geneva, June 25. 1937. Physiological Principles 65 d)ulb temperature.._Eine,_hotc\vire.anemometers are_rapidly replatingjthe use of the Kata thermometer for measuring low air velocities, while some adaptations of the Vernon Globe thermometer, incorporating thermo\ couples rather than mercury thermometers, have been found more satisfactory and convenient. ...__________ ...Avii pi\syj\^,uy i.aiiuicLLeu ciiiu uieir readings ' are compared, can be used for determining the four basic physical factors concerned separately or in certain combinations. The results of the four physical measurements thus determined can generally be translated into the terms of any special instrument combining two or more of them. The worl of the A.S.H.V.E. Research Laboratory has made available psychrometric charts with effective temperature scale superimposed thereon, including Figs. 8 and 9, and others58, while recent studies50 have indicated the degree to which mean radiant temperature of the sur roundings modifies the effective temperature index. In some instances it may be important to record not only the movement and temperature of the air at various levels, but also the temperature of each wall and window, of the flooring, and of the ceiling, and to measure the total effective radiation of the surroundings in 6 directions; in order to trace the exact causes of defects in the building which have an un- favorable influence on the heat exchanges of its inhabitants. Facts of' this type are of great practical importance. * HoUEbtenaVdC. R Y^ W