216 AJsnsruAL report Smithsonian enstitution, 1942 



3 feet. In like manner, radiation of 3000 Angstrom units will require 

 six times as much energy to be as effective as radiation of 2537 Ang- 

 strom units. 



Radiations travel in straight lines. It may therefore be necessary 

 to add reflectors to equipment, but it is important that the reflectors 

 are made of material which will absorb but a minimum amount of 

 the rays. In other instances, especially on exposed foodstuffs, the 

 proper ratio of wave lengths between 1000 to 2000 Angstrom units 

 present in the lamp will convert the oxygen of the air into ozone. 

 The latter, a germicidal agent, will diffuse and reach areas inaccessible 

 to the radiations. In the concentrations present we do not encounter 

 the objectionable features noted when ozone as the sole effective dis- 

 infecting agent must be present in the liigh concentrations usually re- 

 quired. 



In general it can be said that properly designed ultraviolet lamps 

 from which 2537 Angstrom unit wave lengths radiate are available 

 to be used under conditions as advised by engineers. These lights 

 have been found satisfactory in practice after thousands of experi- 

 ments. Where special occasions arise it may be advisable to deter- 

 mine beforehand the necessary electrical characteristics and materials 

 of construction required. 



The use of properly constructed ultraviolet equipment will supply 

 a tool which will be a valuable sanitary aid. One may work freely 

 within the radiated spaces and experience no ill effects. It is ad- 

 visable to wear eye shades or shaded glasses when work is to be 

 carried on at close range or for long periods of time. Imperfect con- 

 trol or overdoses will not produce any poisonous byproduct and will 

 not impart toxicity to the substance or material under treatment. 



APPLICATION 



The use of ultraviolet light of proper intensity, another great scien- 

 tific achievement, is now available as a practical sanitary aid with 

 widespread applications. Equipment, designed and installed at low 

 cost, can be adapted for a great diversity of uses. It will be impossible 

 to consider in detail the wide opportunities for its many applications 

 and the conditions under which it can be and is used. Important facts, 

 however, will be presented revealing its efficiency in certain fields ; and 

 in other instances, attention will be directed merely to many other 

 uses to which this process can be and is being applied. 



SCIENTIST'S AERIAL WAKFAKE 



Bacteria and other microorganisms are present in the air and at- 

 mosphere. The latter serve as transporting agents to enable the organ- 

 isms to gain access to a more favorable environment. The kinds and 



