Document dDqdRrOOz3YDpvqQoYxJbbRqb

112 CHAPTER 6 1956 Guide upon a number of factors, including the dietary and hygienic habits of. the , occupants (frequently reflecting their socio-economic status), the outdoor air supply, air space allowed per person, odor adsorbing capacity , of air conditioning processes, and temperature and relative humidity. The in tensity of odor sensation has been found to vary as the logarithm of the i; % H concentration of the odoriferous substance in the air, or inversely with the logarithmic function of the amount of outdoor air supplied and the air space per person. 4? The relation between air supply and occupancy has been reported by the Harvard School of Public Health2 (Table 1) and the A.S.H.A.E. Research Laboratory.3 Outdoor air requirements for removal of objec tionable tobacco smoke odors are not accurately known, but available information and current practice indicate the need of 15 cfm per person or more.4 . The total quantity of outdoor air to be circulated through an enclosure is often governed chiefly by physical considerations for controlling tern-, perature, air distribution, and air velocity. Other factors which must be taken into consideration, include the type and usage of the building, locality, climate, height of rooms, floor area, window area, extent of occu pancy, and the operation of the system distributing the air supply. Fre SVS.'1 quently, some of these factors, particularly the need for air movement and good distribution, may be satisfied by recirculation of inside air rather I* than outside air. It will be noted that, with adequate air space, the rate of air change sg- indicated in Table 1 is: from 4 to 30 cfm per person. In rooms occupied |g; by only a few persons, such an air change will be automatically attained in cold weather by normal leakage around doors and windows, and can easily be secured in warm weather by the opening of windows. With a |f space allotment of 400 cu ft per person, only 1% air changes per hour are ^ necessary to provide a ventilation rate of 10 cfm per person. . Therefore, in the ordinary dwelling with adequate cubic space allot- ment, no special provision for controlling chemical purity of the air is necessary (aside from removal of fumes from heating appliances). For . such.conditions, the control of air temperature is the major consideration., w In more crowded rooms (large offices, large workrooms, auditoriums), where the cubic space per person is less and it is usually impossible to admit untempered outside air without creating drafts, mechanical ventila tion is essential. The present data regarding the effect of cubic space on outdoor air ffrequirements are not universally accepted. quirements for Comfort Air Conditioning1 The Code of Minimum Re prescribes definite minimum 35 requirements which should be familiar to the designing engineer. It ft '1should be emphasized, however, that the code fixes minimum, rather than adequate requirements. (See also Tables 1 and 3 of Chapter 13.) u Notwithstanding the rapid advance made in air conditioning, some persons still believe there is a stimulating quality'in outdoor air (particularly - ^ country, mountain and seashore air) under ideal weather conditions, which is lacking in artificially conditioned air. It is apparent, however, thatl-p modem air conditioning insures control of the phenomena of nature forthe service and comfort of man independently of weather conditions.' Freedom of movement, action and thought, together with the variability "gf of stimuli experienced by persons under ideal conditions in the country,i|J mountains or seashore, undoubtedly has some stimulating effect. Various; *4' experimenters have attempted to duplicate the invigorating qualities, ofilf 'ill Physiological Principles Table 1. Minimum Outdoor Aib Requirements to Remove Objectionable Body Odors Under Laboratory Conditions* Ttpb op Occupants Am Space per Person Cu Ft Outdoor Air Supplt CFM per Person Hea'ting season with or without recirculation. Air not condit oned. Sedentary adults of average socio-economic status....^ Laborers......... jGrade schoolchildren of average socio-economic status Grade school children of lower socio-economic status. . Children attending private grade school** 100 200 300 500 200 100 200 300 500 200 100 25 16 12 7- . 23 29 21 17 11 38 22 ` Sedentary Adults__ 200 12 Summer season. Air cooled and dehumidified by means ofa spray dehumidifier. Spray water changed daily. Total air circulation SO cfm per person. Sedentary Adults.. 200 <4 outdoor air by the use of ozone, ionization, or ultra-violet light, but results to date have been inconclusive or negative.6 Ozone in amounts of 0.01 to 0.05 ppm of air is allowable in comfort aii conditioning. Above this limit there is .a pungent, unpleasant odor 'and perhaps respiratory distress, depression, and stupor.6 PHYSICAL IMPURITIES IN AIR Dust particles of almost any type can produce irritation of the mucous membranes of the nose and throat, if present in high concentrations. Cer tain dusts may be very harmful,-but coal dust, is tolerated well. .The effects of various industrial dusts, pollens, etc., are discussed in Chapter 8. A certain part of the dissemination of disease in confined spaces may be due to pathogenic organisms floating in the air like dust particles. (See Chapter 7). ... While in some instances it may be possible to reduce the physical im purities of the air by dilution from a non-contaminated source, such a source is rarely available. Frequently, outdoor air contains a higher con centration of physical impurities than indoor air. Therefore, it is usually desirable to reduce the concentration of physical impurities by air clean ing methods. (See Chapter 34.) THERMAL INTERCHANGES WITH ENVIRONMENT Body temperature depends upon the balance between heat production and heat, loss. Heat resulting from oxidation in the body (metabolism)