Continuous Vs. Pulsed UV-C

Some companies claim that pulsed xenon is a more effective way to kill harmful bacteria.  Claiming similarities to a punch of a fist on a wall, more punches will weaken it better than one punch.  However, light is not a fist.  Light is a form of energy, and continual energy is more effective than turning it on and turning it off.

The study below agrees:

VA Donskey study
Graph 1 – Chart from VA Donskey study: Study results showing log reductions achieved by a UV-C and pulsed xenon devices when run for the same time (10 min.) at the same distance from glass microscope slides (4 ft). (PRNewsFoto/Infection Prevention Tecnologies)

AUBURN HILLS, Mich., March 31, 2015 /PRNewswire-USNewswire/ — The efficacy of continuous UV-C disinfection robots versus pulsed xenon (PU-UX) was highlighted in a recently published study1 of ultraviolet (UV) light disinfection systems by an influential infection prevention research team, including Curtis Donskey, M.D.  The study tested a continuous UV-C robot which was run for the same length of time from the same point in the room as a pulsed xenon (PU-UV) unit.  The results showed surprisingly low pathogen kill rates for the pulsed xenon device, about .5 log for both C.diff and VRE, even as close as 4 feet1 (see photo).  The continuous UV-C robot clearly demonstrated a much higher CFU reduction for the pathogens C. difficile, MRSA and VRE.  The study states, “PX-UV was less effective than continuous UV-C in reducing pathogen recovery on glass slides with a 10-minute exposure time in similar hospital rooms”and “the UV-C device achieved significantly greater log10CFU reductions than the PX-UV device” 1 (emphasis added).  It’s important to note that not only did the continuous UV-C robot in the study show much stronger disinfectant results, but that it was not run for its entire cycle time.

The study calls attention to the dangers of trying to complete a disinfectant procedure too quickly and under-dosing as a result.  The study states, “Although the PX-UV device reduced contamination on surfaces, residual contamination was not uncommon”1 and “the log reduction achieved by PX-UV on carriers at 10 minutes were relatively modest.” 1 “In an effort to speed up the cleaning process, EVS and IP staffs may be misleading themselves about how well the pulsed xenon treated rooms are really disinfected,” says Kenny.  “Hospitals must be wary of bold claims of speed and efficacy made by manufacturers of pulsed xenon units that simply don’t stand up to scrutiny as clearly shown in the Donskey study.