Document p299VR1qajpB87kdyrX8bjyNX

HEATING VENTILATING AIR CONDITIONING GUIDE 1944 during the past lew years, there still remain those who believe in a Superior, stimulating quality of outdoor air (particularly country, moun tain and seashore air) under ideal weather conditions, as compared with properly conditioned air. While this point of view is usually held by persons not intimately acquainted with the complicated factors involved they nevertheless carry some weight. It is apparent, however, to anyone acquainted with the factors involved and the conditions effecting comfort that in modern air conditioning, like in most other branches of engineering, modern science makes it possible to control the phenomena of nature for Table 1. Minimum Outdoor Air Requirements to Remove Objectionable Body Odors8 s Type or Occupants Space per Person Co Ft Outdoor Air Supply cfm per Person Heating season with or without recirculation. Air not conditioned. Sedentary adults of average socio-economic status-- Sedentary adults of average socio-economic status-- Sedentary adults of average socio-economic status.-- Sedentary adults of average socio-economic status.-- 100 200 300 500 25 16 12 7 Laborers. Grade school children of average class............................ Grade school children of average class........................-- Grade school children of average class------ ----------------Grade school children of average class............................ 200 100 200 300 500 23 29 21 17 11 Grade school children of poor class.-------------------------- 200 38 Grade school children of better class.--.......................... 200 18 Grade school children of best class................................... 100 22 Heating season. Air humidified by means of centrifugal humidifier. Water atomization rate 8 to 10 gph. Total air circulation SO cfm per person. Sedentary Adults------- --------------- --........ -----................ 200 12 Summer season. Air cooled and dehumidified by i wans of a spray i thumidifier. Spray water changed daily. Total air circu. ation SO cfm per person. 200 <4 the service and comfort of man beyond any possibilities found in nature itself. When the requirements for optimum comfort as determined by the atmospheric environment are known (and the comprehensive studies to date lead us to believe that they are known at least to a high degree), the air conditioning engineer can supply these requirements indoors to the same perfection as may accidentally be found at times outdoors and keep them under control. The freedom of movement, action and thought; together with the variability of stimulae experienced by persons under ideal conditions in the country, mountains or seashore, and the psycholog ical effect of these wide open spaces undoubtedly have some stimulating *Loc. Cit. Note 3, p.'156. CHAPTER 2. PHYSIOLOGICAL PRINCIPLES effect, which when compared with the monotony of confinement indoors even in the most favorable atmospheric environment accounts for the contrast. Ultra-violet light and ionization have been suggested but the evidence so far is inconclusive or negative9. Ozone has been used with success for the destruction of micro-organisms (molds) in meat packing establishments'and the like; and where con siderable amounts of organic effluvia are present it may be useful as a deodorant. For ordinary ventilation practice, however, neither of these purposes can be usefully attained, since the concentration of ozone necessary for effectiveness would be likely to transcend the limit of com fort in ordinary occupied rooms. While ozone has been used in the treatment of certain diseases, there is no evidence that it has a tendency to increase comfort or to benefit health under conditions of normal human occupancy. The allowable concentrations in the breathing zone are very small, between 0.01 to 0.05 ppm parts of air. These are much too small to influence bacteria. Higher concentrations are associated with a pungent unpleasant odor and considerable discomfort to the occupants. One part per million causes respiratory discomfort, headaches, depression, a lowering of the metabolic rate and may even lead to coma10. PHYSICAL IMPURITIES IN AIR Dust particles of various types, when present in considerable con centrations, produce an irritant effect upon the mucous membranes of nose and throat and may be associated with high prevalence of acute respiratory diseases such as bronchitis - and pneumonia. Dust which contains free silica has special harmful effects, causing a primary disease of the lungs (silicosis) and predisposing the victim in a high degree to tuberculosis. These, however, are special problems of industrial hygiene which will not be discussed in detail in this chapter. A certain part of the dissemination of disease in confined spaces is caused by the emission of pathogenic organisms from infected persons. Droplets sprayed into the air in talking, coughing, sneezing, etc., do not all fall immediately to the ground within a few feet from the source, as was formerly believed. The large droplets do, of course, but minute droplets less than 0.1 mm in diameter evaporate to dryness before they fall the height of a man. Nuclear residues from such sources, which may contain infective organisms drift long distances with the air currents and the virus may remain alive long enough to be transmitted to other persons in the same room or building. Droplet nuclei have been recovered from cultures of resistant micro-organisms a week after innoculation into a tight chamber of 3000 cu ft capacity, although the majority of disease A.S.H.V.E. Research Report No. 921--Changes in Ionic Content in Occupied Rooms, Ventilated by Natural and Mechanical Methods, by C. P. Yaglou, L. C. Benjamin and S. P. Choate (A.S.H.V.E. Trans actions, Vol. 38,1932, p. 191). A.S.H.V.E. Research Report No. 965--Physiologic Changes During Ex posure to Ionized Air, by C. P. Yaglou, A. D. Brandt and L. C. Benjamin (A.S.H.V.E. Transactions, Vol. 39,1933. p. 357). A.S.H.V.E. Research Report No. 985--Diurnal and Seasonal Variations in the Small Ion Content ol Outdoor and Indoor Air, by C. P. Yaglou and L. C. Benjamin (A.S.H.V.E. Transactions, Vol. 40, 1934. p. 271). The Nature of Ions in Air and Their Possible Physiological Effects, by L. B. Loeb (A.S.H.V.E. Transactions, Vol. 41,1935, p. 101). The Influence of Ionized Air upon Normal Subjects, by L. P. Herrington (Journal Clinical Investigation, 14, January, 1935). The Effect of High Concentrationsof Light Negative Atmospheric Ions on the Growth and Activity of the Albino Rat, by L. P. Herrington and Karl L. Smith (Journal Ind. Hygiene, 17, November, 1935).' Subjective Reactions of Human Beings to Certain Outdoor Atmospheric Conditions, by C.-E. A. Winslow and L. P. Herrington (A.S.H.V.E. Transactions. .Vol. 42, 1936. p. 119). TMTh* British Medical Journal, Editorial, June 25, 1932, p. 1182. See also Loc. Cit. Note 9. 45