214 AISTNUAL REPORT SMITHSONIAN INSTITUTION,, 1942 



cidal effect (2537 Angstrom units). In the case of a fluorescent 

 lamp, the powder present on the inside is activated and fluorescence 

 is produced. In the case of the ultraviolet lamp, the ultraviolet 

 radiations generated pass through a special type glass used in making 

 the lamps. This glass is f)urposely chosen as it will allow the passage 

 of the selected waves of ultraviolet radiation of greatest germicidal 

 power and at the same time absorb most of the objectionable ultra- 

 violet wave lengths in the ozone-producing region. The low vapor 

 pressure and low current density in the lamp also reduce to a min- 

 imum the radiations emitted in the visible spectrum. Ultraviolet 

 lamps radiate energy of wave length ranging from 2000 to 2800 

 Angstrom units and, as mentioned previously, most of the radiations 

 are 2537 Angstrom units in length. Inasmuch as most of the radia- 

 tions are not visible, individuals are prone to forget that ultraviolet 

 lamps when operated should not be viewed by unprotected eyes for 

 long periods of time or especially at close range, as a conjunctivitis 

 may develop. 



Equipment provided with suitable ultraviolet lamps has been 

 designed to fill practically all needs. These lamps are marketed 

 under different trade names, among the latter being the Sterilamp, 

 Germicidal Lamp, Safe-T-Aire Lamp, and the Saniray. Tlie 

 lamps are designed usually to operate on alternating current through 

 a low-capacity transformer. If only direct current is available, a 

 converter unit is necessary. Several lamps, wired in series, never 

 in parallel, can be operated from one transformer. The lamps are 

 lighted on the turn of the switch. Other than keeping them clean, 

 there is no more attention required than is necessary for an electric 

 bulb. These lamps are available in different sizes for use in all kinds 

 of fixtures, a fixture and ultraviolet lamp being a complete unit in 

 itself. After long use and even at low temperatures, the lamp may 

 show some discoloration, the latter in turn absorbing some of the 

 ultraviolet rays. Ultraviolet lamps have a more effective life when 

 operated at temperatures above 40 degrees F. Under average con- 

 ditions of use, they will operate for many thousands of hours, giving 

 a continued service for at least 6 months (4,500 hours) before re- 

 placement becomes necessary. 



SANITIZATION 



You are familiar with the term "sterilization" which, speaking 

 broadly, refers to the destruction of every form of life, visible or 

 invisible, harmful or innocuous. The term "germicide," referring to 

 agents which kill germs, is used synonymously with the term "bac- 

 tericide" signifying only those agents which destroy bacteria. The 

 term "pasteurization," previously mentioned, refers to a process which 

 subjects products affected by heat to temperatures sufiicient to destroy 



