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Terminal Decontamination of Patient Rooms Using an Automated Mobile UV Light Unit

  • John M. Boyce (a1) (a2), Nancy L. Havill (a1) and Brent A. Moore (a3)



To determine the ability of a mobile UV light unit to reduce bacterial contamination of environmental surfaces in patient rooms.


An automated mobile UV light unit that emits UV-C light was placed in 25 patient rooms after patient discharge and operated using a 1- or 2-stage procedure. Aerobic colony counts were calculated for each of 5 standardized high-touch surfaces in the rooms before and after UV light decontamination (UVLD). Clostridium difficile spore log reductions achieved were determined using a modification of the ASTM (American Society for Testing and Materials) International E2197 quantitative disk carrier test method. In-room ozone concentrations during UVLD were measured.


For the 1-stage procedure, mean aerobic colony counts for the 5 high-touch surfaces ranged from 10.6 to 98.2 colony-forming units (CFUs) per Dey/Engley (D/E) plate before UVLD and from 0.3 to 24.0 CFUs per D/E plate after UVLD, with significant reductions for all 5 surfaces (all P<.02). Surfaces in direct line of sight were significantly more likely to yield negative culture results after UVLD than before UVLD (all P<.001). Mean C. difficile spore log reductions ranged from 1.8 to 2.9. UVLD cycle times ranged from 34.2 to 100.1 minutes. For the 2-stage procedure, mean aerobic colony counts ranged from 10.0 to 89.2 CFUs per D/E plate before UVLD and were 0 CFUs per D/E plate after UVLD, with significant reductions for all 5 high-touch surfaces. UVLD cycle times ranged from 72.1 to 146.3 minutes. In-room ozone concentrations during UVLD ranged from undetectable to 0.012 ppm.


The mobile UV-C light unit significantly reduced aerobic colony counts and C. difficile spores on contaminated surfaces in patient rooms.


Corresponding author

Hospital of Saint Raphael, 1450 Chapel Street, New Haven, CT 06511 (


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Terminal Decontamination of Patient Rooms Using an Automated Mobile UV Light Unit

  • John M. Boyce (a1) (a2), Nancy L. Havill (a1) and Brent A. Moore (a3)


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