APPLICATIONS AND SOURCES OF ULTRAVIOLET 



IIO" 10 0° 90° 80° 70° 60° 50° 40" 30° 20° 



73 



1 2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17 18 19 20 

 DISTANCE FROM FIXTURE, ft 



Fk;. 2-14. (a) Spatial distribution of ultraviolet from typical bactericidal tubes and 

 louvered reflectors. (6) Isointensity lines in milliwatts per square foot in a plane 

 perpendicular to the center of the G30T8 tube of Fig. 2-9. 



Barrier-type units have usually been custom made, but a typical 

 combination unit is described by Fig. 2- 15a and h. 



HEALTH VALUE OF AIR DISINFECTION 



Ultraviolet air disinfection is but one of the factors in a complete air 

 sanitation. It is comparable with the removal of dust and noxious 

 vapors. Although air disinfection has been used in industrial applications 

 as such a general sanitary measure, it early came to be thought of as 

 having more specific possible value in preventive medical and public- 

 health applications. Buttolph (1951) has proposed a tentative standard 

 of air sanitation relating ventilation and disinfection to room occupancy. 

 It calls for one air change per miimte where there may be as little as 300 

 cu ft of room volume per occupant. From that it assumes the need for 

 dilution with fresh air or eciuivalent ultraviolet air disinfection to be 

 proportional to the crowding, to vary dii-ectly with the iuiml)er of occu- 

 pants in a room and inversely with its volume. 



