Impact of Room Location on UV-C Irradiance and UV-C Dosage and Antimicrobial Effect Delivered by a Mobile UV-C Light Device

Abstract

OBJECTIVETo evaluate ultraviolet C (UV-C) irradiance, UV-C dosage, and antimicrobial effect achieved by a mobile continuous UV-C device.DESIGNProspective observational study.METHODSWe used 6 UV light sensors to determine UV-C irradiance (W/cm2) and UV-C dosage (µWsec/cm2) at various distances from and orientations relative to the UV-C device during 5-minute and 15-minute cycles in an ICU room and a surgical ward room. In both rooms, stainless-steel disks inoculated with methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus (VRE), and Clostridium difficile spores were placed next to sensors, and UV-C dosages and log10 reductions of target organisms achieved during 5-minute and 15-minute cycles were determined. Mean irradiance and dosage readings were compared using ANOVA.RESULTSMean UV-C irradiance was nearly 1.0E-03 W/cm2 in direct sight at a distance of 1.3 m (4 ft) from the device but was 1.12E-05 W/cm2 on a horizontal surface in a shaded area 3.3 m (10 ft) from the device (P<.001). Mean UV-C dosages received by UV-C sensors located at different distances and orientation relative to the device varied significantly during 5-minute cycles and during 15-minute cycles (P<.001). Log10 reductions ranged from >4 to 1–3 for MRSA, >4 to 1–2 for VRE and >4 to 0 log10 for C. difficile spores, depending on the distance from, and orientation relative to, the device with 5-minute and 15-minute cycles.CONCLUSIONUV-C irradiance, dosage, and antimicrobial effect received from a mobile UV-C device varied substantially based on location in a room relative to the UV-C device.Infect Control Hosp Epidemiol 2016;37:667–672

A comparison of the efficacy of multiple ultraviolet light room decontamination devices in a radiology procedure room

“…Previous studies have demonstrated that exposure times of 10 minutes or longer may provide sufficient UV-C dosing to reduce C. difficile spores by 2 logs or more. 18,[20][21] Our study has some limitations. We assessed contamination of the radiology department with a single point-prevalence culture survey.…”

“…Our findings are consistent with 3 recent reports in demonstrating that measurements of irradiance may be useful in understanding decontamination performance of different devices. [20][21][22] If a radiometer is available, measurement of irradiance can be completed quickly and easily. Alternatively, commercial test cards can provide a simple and easy-to-use colorimetric assessment of UV output.…”

Understanding ultraviolet light surface decontamination in hospital rooms: A primer

“…6,7 A multicenter, randomized controlled trial of a mobile UV device and other smaller studies have shown that UV devices can decrease surface contamination and reduce healthcare-associated infections (HAIs); effect size is dependent upon the type of microorganisms and the type of disinfectant used in the comparator groups. [8][9][10][11][12][13][14] A recent systematic review and meta-analysis of no-touch disinfection technologies evaluated 13 studies that used UV devices. 15 When the results of the studies were pooled, statistically significant reductions in the rates of infections caused by Clostridioides difficile.…”

“…7,16 Determining the effectiveness of devices is complicated by lack of standard methods for testing UV-C devices, limited published data on the doses of UV delivered to various surfaces in patient rooms, and conflicting data on the UV dose (fluence) necessary to achieve desired reductions of various healthcare pathogens, including C. difficile. 12,[17][18][19][20][21][22][23][24] Healthcare personnel would benefit from a basic understanding of the characteristics of UV-C, the availability of more evidence on the UV-C doses delivered to surfaces in patient rooms, and knowledge of the UV-C doses required to reduce specific healthcare pathogens.…”

Efficacy of UV-C disinfection in hyperbaric chambers

“…8 Our log 10 reductions of 6 or higher for MRSA are larger than those of prior studies, most likely due to differences in inoculum size. 9,10 Our study has several limitations. We sampled Formica sheets instead of sampling directly from clinical surfaces.…”