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1945 Theatre Catalog, 4th Edition, Page 513 (487)

1945 Theatre Catalog, 4th Edition
1945 Theatre Catalog
1945 Theatre Catalog, 4th Edition, Page 513
Page 513

1945 Theatre Catalog, 4th Edition, Page 513

this has been recorded photographically, there is presented here a series of pictures showing the destruction of paramoecia.

Bactericidal action is determined by the amount of radiation to which the bacteria are exposed, regardless of whether a high intensity is applied for a short time or a low intensity applied for a correspondingly longer period.

The resistance of bacteria to ultraviolet'radiation varies appreciably at different stages of the individuals life history.

The lethal action is not influenced by the temperature or humidity. It is the result of direct radiation apart from any environmental considerations.

The killing power of the lamps decreases as the distance from the lamp increases. For example, a given bacterium will be killed twice as quickly at three inches as a similar bacterium would be at six inches from the light source. There does not seem to be any stimulant effect by ultraviolet light, regardless of how low the concentration may be. The lethal power still effective at a distance of 18 feet from the lamp, provided the period of irradiation is sufiiciently prolonged.

Maintenance and Replacement

Germicidal lamps require little in the way of maintenance other than the extremely important, periodic cleaning. Dust and dirt collection will interfere with the transmission of ultraviolet radiation. Paper towels moistened with alcohol or water have been found to be effective in wiping grease and dirt from lamps.

When being serviced in any way, germicidal lamps should be shut off, since exposure of the eyes to ultraviolet will produce painful conjunctivitis. If testing lamps or other reason requires coming in close proximity to ultraviolet radiation, a protective hood should be worn.

While these lamps do not ordinarily burn out, the ultraviolet output does decrease, falling below the specified requirements after 4,000 to 4,500 hours of use. Each lamp, accordingly, should be replaced after it has been in active service a full year.

For easy measuring of the amount of ultraviolet radiation, a meter, with a direct-reading indicator, and small enough to be carried conveniently in the pocket, is available. .

Lamps are inserted or removed from receptacles, in duct installations, by loosening the metal ferrule on one receptacle and sliding it back about two inches to allow clearance for the lamp over the edge of the receptacle. When the lamp is in place, the receptacles are pulled forward and the ferrule is tightened in place.

Maintenance economy can be gauged by the fact that the Hygeaire 36-inchtube model consumes less electricity than an ordinary bulb suitable for reading purposes. An electrical input of only 40 watts is all that the unit requires to produce 7.2 watts of germicidal ultraviolet energy. The low operating cost, including tube replacements and electricity, averages less than three cents a day for every 1,000 cubic feet of room volume. The 30-inch Westinghouse Sterilamp consumes about the same amount of



electricity as does an ordinary 25-watt light bulb.


Germicidal lamps may be utilized in theatres in two ways, in specially-designed flxtures and in batteries placed within air-conditioning system. Since the latter may seem to be more desirable, it has been considered in greater detail by another autors, but unit utilization must be seriously considered.

It is desirable to have indirect radiation of the air above eye level in the theatre auditorium. If the air from a heating or conditioning system enters the room near the ceiling and leaves through vents near or on the fioor, all the air above a six or seven foot level will be irradiated by germicidal ultraviolet units if these are placed along the walls. Where there are balconies, the placement of the lamps must be such as to prevent the direct rays from reaching the eyes of patrons in the balconies.

Louvres at right angles to the tubular lamp, spaced closely enough to hide the source of radiation, will prevent eye irritation but will absorb some of the germicidal rays. These louvres or shields must have non-refiecting surfaces. The fixtures should be constructed to prevent any of the visible bluish light from striking the wall above the fixture. Lighting of the walls not only may detract from the stage or screen lighting but also may result in fading of the wall finish or draperies. The distance of the fixture from the ceiling or the opposite wall is usually great enough to insure only a very small amount of visible refiection from those surfaces and no fading or interference with stage or screen. If the direction of air fiow in the auditorium is

toward the ceiling the arrangement of the lamp fixtures is quite the same as for downward air fiow. In either case the germs from an infected person will be carried downward to the air outlet or upward into the irradiated area and seldom reach adjacent persons without first passing through an ultraviolet barrier. Auditoriums equipped with indirect germicidal ultraviolet radiation can be occupied with very little danger of spreading infections such as measles, mumps or colds as such germs and viruses are easily killed by the radiations. Tests made in school rooms in which indirect radiation was installed indicate a reduction in communicable infections to one third and even to one fifth of those in adjacent rooms where no radiation was used. There is greater protection against cross infection where the radiation is installed in the room itself than where it is necessary to place the lamps in the air duct or plenum chamber On an air-conditioning system. The air supplied to the room can be made practically germ free but there is always the chance that infection from one person may travel to another in the same room. The general level of contaminatiOn can be reduced by the constant addition of germ free air to the room and the removal of contaminated air. Under these conditions the level of contamination depends upon the number of air changes per hour and the number of persons in the room.

GE Germicidal Lamps

To those who congregate in theatres and public buildings, the General Electric Company germicidal lamps offer the equivalent of 100 changes of fresh air every hour. This fresh air means a hitherto impossible control of air-borne in HOW ULTRAVIOLET LIGHT KILLS micro-organisms is shown in this remarkable series of pictures. Upper leftnormal paramoecia (commonly called, because of their shape, "slipper animalcules") in their natural condition. Upper right-After but 30 seconds of treatment by ultraviolet radiation, they become distended. Lower leftThe distention continues with the exposure, the swelling becoming pronounced blisters where the cell walls hoye become weakened. Lower right-Finally, the internal pressure becoming too great, the organisms literally explode. Although bacteria cannot be photographed like this, the killing process is the same. (Westinghouse photo.)
1945 Theatre Catalog, 4th Edition, Page 513