Document 2JK02q4pZQ32wBXwYy06pMvDg

of and 1936American Society Heating Ventilating Engineers Guide, mately the same value in July, August and September, and although the average monthly temperature did not vary much, the prevailing outdoor temperature ranged from 70 F to 99.5 F. A decrease in the optimum temperature became apparent only when the prevailing outdoor tempera ture fell to 66 F, which is below the customary, room temperature in the United States for summer and winter. Young men as a general rule prefer conditions in the cool region of the comfort zone, and women and older people in the warm region of the comfort zone. Crowding the experimental chamber lowered the optimum effective temperature from 70.8 deg when the gross floor area per occupant was 44 sq ft and the air space 380 cu ft, to 69.4 deg when the floor area was reduced to 14 sq ft and the air space to 120 cu ft per occupant. In the comfort zone experiments of the A.S.H.V.E. Research Labora tory,the relative humidity was varied between the limits of 30 and 70 per cent approximately, but the most comfortable range has not been deter mined. In similar experiments at the Harvard School of Public Health, a relative humidity of 70 per cent was found to be somewhat humid in winter, by. about half of the subjects who were stripped to the waist, even when the dry-bulb temperature was 70 F or less. In summer, a relative humi dity of 30 per cent was pronounced as o little too dry by about a third of the subjects wearing warm-weather clothing. So long as the temperature was kept within proper limits, the majority of the subjects were unable to detect sensations of humidity (i.e., too high, too low, or medium) when the relative humidity was between 30 and. 60 per cent. This is in accord with studies by Howell23, Miura24 and others. Dry air produces an excessive loss of moisture from the skin and respira tory tract. Owing to the cooling effect of evaporation, higher tempera tures are necessary, and this condition leads to discomfort and lassitude. Moist air, on the other hand, interferes with the normal.evaporation of moisture from the skin, and again may cause a feeling of oppression and lassitude, especially when the temperature is also high. Just what the optimum range of humidity is, is a matter of'conjecture. There seems to exist a general opinion, supported by some experimental and statistical data, that warm, dry air is less pleasant than air of a , moderate humidity, and that it dries up the mucous membranes in such a way as to increase susceptibility to colds and other respiratory disorders23- 2B- 27. For the premature infant, a high relative humidity of about 65 per cent is demonstrably beneficial to health and growth28, and according to Huntington29, this seems to be the case for adults also. All of these "Humidity and Comfort, by W. H. Howell (The Science Press, April, 2931). "Effect of Variation in Relative Humidity upon Skin Temperature and Sense of Comfort, by U. Miura (American Journal of Hygiene, Vol. 13, 1931. p.'432). v "Reactions of the Nasal Cavity and Post-Nasal Space to Chilling of the Body Surface, by MuddrStuart, et ai (Journal Experimental Medicine, 1921, Vol. 34, p. 11). "Reactions of the Nasal Cavity and Post-Nasal Space to Chilling of the Body Surfaces, by A. Goldman, et al and Concurrent Study of Bacteriology of Nose and Throat (Journal Infectious Diseases, 1921, Vol. 29, p. 151). / "The Etiology of Acute Inflammations of the Nose. Phhrynx and Tonsils, by Mudd, Stuart, et al (Am. Otol.. Rhino!., and Laryngol., 1921). > "Applicationof Air Conditioning to Premature Nurseries in Hospitals', by C. P. Yaglou, Philip Drinker and K. D. Blackfan (A.S.H.V.E. Transactions, Vol. 36, 1930). "Weather and Health, by Ellsworth Huntington (Bulletin of the National Research Council No. 75. The National Academy of Science, Washington. D. C., 1930). 70 TThapter 3--Ventilation and Air Conditioning Standards studies indicate that the optimum humidity must always be considered in combination with temperature. Until more exact information is secured, it would be desirable to restrict the comfort .zones to the range of relative humidity employed in the comfort zone experiments, namely, 30 to 70 per cent. Relative humidities below 30 per cent may prove satisfactory from the standpoint of comfort, so long as extremely low humidities are avoided. From the standpoint of health, however, the consensus seems to favor a relative humidity between 40 and 60 per cent. In mild weather such comparatively high relati- e humidities are entirely feasible, but in cold or sub-freezing weather they are objectionable on account of condensation and frosting on the windows. They may even cause serious damage to certain building materials of the exposed walls by condensation and freezing of the moisture accumulating inside these materials. Unless special precautions are taken .to properly insulate the affected surfaces, it will be necessary to reduce the degree of artificial humidification in sub-freezing weather to less than 40 per cent, according to the outdoor temperature. Information on the prevention of condensation on building surfaces is given in Chapter 7. The principles underlying humidity requirements and limitations are discussed more fully elsewhere39. The comfort chart (Fig. 5) applies to.adults between 20 and 70 years of age living in the northeastern parts of the United States. For pre maturely born infants, the optimum temperature varies from 100 F to 75 F, depending upon the stage of development. The optimum relativ e humidity for these infants is placed at 65 per cent. No data are yet available on the optimum air conditions for full term infants and young children up to school age. Satisfactory air conditions for these age groups are assumed to vary from 75 F to 68 F with natural indoor humidi ties. For school children, the studies of the New York State Commission on Ventilation place the optimum air conditions at 66 F to 68 F tempera ture with a moderate humidity (not specified) and a moderate but not '* -/ . * r *\i Satisfactory comfort conditions are found to vary from 40 deg to 70 deg ET, depending upon the rate of work and amount of clothing worn.- The effective temperatures giving maximum comfort for persons working have been determined by the A.S.H.V.E, Research Laboratory32 for a rate of work which is considered hard labor. For this degree of work, 50 per cent were fairly comfortable for temperatures ranging from 46 to 64 deg ET, while the greatest percentage found maximum comfort at 53 deg ET, In hot industries, SO deg ET is considered the upper limit compatible with efficiency, and, whenever possible, this should be reduced to 70 deg ET or less. ' i APPLICATION OF COMFORT CHART The average winter comfort line (66 deg ET) applies to average American men and women living inside the broad geographic belt across "Humidification for Residences, by A. P. Krati (University of Illinois Engineering Experiment Station Buttelin No. 230. July 28, 1931). - "Ventilation, Report of the New York State Commission on Ventilation, 1923. "A.S.H.V.E. research paper entitled Heat and Moisture Losses from Men at Work and Application to Air Conditioning Problems, by F. C. Houghten, W'. W. Teague, W. E. Miller aud W. P. Yant (A.S..H.V.E. Transactions. Vol. 37. 1931). 71 X