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1945 Theatre Catalog, 4th Edition, Page 518 (492)

1945 Theatre Catalog, 4th Edition
1945 Theatre Catalog
1945 Theatre Catalog, 4th Edition, Page 518
Page 518

1945 Theatre Catalog, 4th Edition, Page 518

Since, in breathing the air of a crowded room, one is actually inhaling to some extent the nasopharyngeal iiora of other occupants of the room, it is desirable to apply adequate procedures for the circulation and dilution of the air. Under theoretically ideal conditions the displacement of air from a room by blowing in purified air from the outside in an amount equal to the volume of the room (one turnover) will reduce the concentration of dispersed micro-organisms to approximately 37 per cent of the original value. During winter months, when rooms are kept closed, ventilation occurs chiefly through the seepage of air around windows and doors, accounting for less than ten turnovers. of air an hour. Sanitary ventilation is defined in terms of the venting of air-borne micro-organisms, that is, the number of turnovers of air an hour required to reduce the number of micro-organisms to the unit volume to a concentration level equivalent to that resulting from their killing by chemical or physical agencies. The removal of organisms can take place by transfer in air currents; chemical destruction, kill FIGURE 2.-The complete Hygeaire assembly consists of a specially designed reflector, reflector housing, bactericidal lump, baffle, conductor cord, and plug. The fixed baffle is one of the special features of the Hygeoire, serving to protect the eyes and skin of occupants in the irradiated space against a possible coniunctivitis

ing by irradiation, or displacement during washing or filtration. Any method resulting in reduction equivalent to 25 to 100 turnovers of air an hour is considered to give fair sanitary ventilation, while reduction equivalent to less than 10 turnovers represents poor sanitary ventilation.

A draft is produced when air is changed more often than six times an hour or if the velocity of air How is more than 3 to 31/; feet a second. Therefore, adequate sanitary ventilation must depend on means other than normally induced air iiow. The eiiiciency of a ventilating system is ordinarily based on the balance between micro-organisms removed by ventilation and those introduced during the same time by occupants of the space concerned. The economics of air conditioning demand that 50 to 90 per cent of the air be recirculated after making adjustments for temperature and humidity.

Thirty cubic feet of fresh air a minute for each person, or the ttmake-upii air in the most efficient heating and ventilating systems, provides approximately


six air changes an hour or one change every ten minutes. This degree of ventilation dilutes the air contamination at such a rate as to require a full hour for practically complete disinfection of a recently vacated room.

It is believed that, for the prevention of the spread of respiratory diseases by air-borne bacteria and Viruses, an air purity equal to that of summer living conditions (60 to 120 air changes an hour) must be provided. Figure 1 illustrates the decontamination and disinfection effectiveness of air changes and air change equivalents to the hour.

The installation of the Hygeaire system has made practicable air-change equivalents of 100 to 500 an hour, which is considered to be excellent sanitary ventilation. Micrmorganisms, ejected in droplets and suspended in the air are destroyed by this means at a rate far greater than can be accomplished by any known method of mechanical ventilation. The practical results of the Hygeaire system of sanitary ventilation can be measured directly by determining the bacterial content of the air from the irradiated space.

or erythema by confining the direct beam to the room area above the line of vision. The reflector housing is designed to insure a permanent control on the reflector, to provide a mounting for the baffle, and to permit exposed surface or recessed mounting. Stock reflector housings are available in white or cream white.

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1945 Theatre Catalog, 4th Edition, Page 518