Germicidal Irradiation Research Articles

Sterilization Ability by Microwave UV-ozone Generator

The 253.7 nm UV light emitted from mercury lamps is known as germicidal radiation. Additionally, it emits UV light with a shorter wavelength of 184.9 nm. This UV wavelength can generate ozone (O3) from oxygen molecules (O2) in the air. Ozone has been shown to effectively inactivate various pathogenic microorganisms. However, they must decompose quickly because they are harmful to the human body. Methods for decomposing ozone include a thermal decomposition method, a chemical cleaning method, an activated carbon method, and the like. However, there is no practical or efficient treatment method. Ozone generation methods include the silent discharge method, electrolytic method, photochemical reaction method, high-frequency discharge method, and radiation method. The most efficient method is silent discharge, which is concerned with nitrogen oxide (NOX) generation caused by nitrogen molecules in the air, and deterioration of the electrodes during use is problematic. Furthermore, nitrogen oxides react with water in the gaseous phase to produce nitric acid. Nitric acid reacts with several metals to form nitrates. A sterilization device using highconcentration ozone has not been put to practical use because of the lack of an efficient method for decomposing ozone and the corrosion of metals. The UV-ozone generation method using microwave plasma used in this study can generate UV light by applying 2.45 GHz microwaves to a quartz electrodeless bulb filled with mercury. By changing the glass material and emitting UV light at different wavelengths, it is possible to develop a UV-ozone generator that can selectively generate and decompose ozone. Furthermore, since 184.9 nm UV specifically acts on oxygen molecules, NOX is not generated. Additionally, 253.7 nm UV, which is emitted at the same time as 184.9 nm UV, can easily decompose ozone into O2

Application of cold atmospheric plasma for mold inactivation

Mold growth in indoor interiors is an increasing problem that has adverse effects on both occupants and building materials. The aim of this study was to present the new environmentally friendly method (cold atmospheric plasma treatment) for decontamination of indoor environments contaminated by mold spores, with the potential to become an effective replacement for conventional methods, such as ultraviolet-C (UV-C) germicidal irradiation. The spores of Aspergillus species on malt extract agar plates were exposed to plasma produced by diffuse coplanar surface barrier discharge. The surface coverage of mold was evaluated using image analysis. Cold plasma treatment inactivated spores on the surface of the culture medium in 0.5 min, whereas a weak growth delay was observed after 30 minute exposure to UV-C irradiation. This study demonstrated that cold atmospheric plasma is a more effective method for reducing mold spores on agar compared with germicidal UV-C irradiation.

Analysis of New Standards in the Field of UV - C Disinfection

The coronavirus pandemic continues to plunge the world into waves of a potentially deadly disease caused by multiple strains of the SARS-CoV‑2 virus. A well-known effective method of non-specific prevention of the spread of respiratory viral infections in the Russian Federation is air disinfection using ultraviolet (UV) germicidal irradiation. Today, in medical institutions the application of this technology bases on domestic guidelines developed without taking into account the characteristics of new viruses, new knowledges and technologies in the field of UV radiation generation. A number of new standards have been issued abroad, significantly deepening the knowledge and capabilities in the development and application of UV disinfection devices. This article provides an overview of new standards, highlights the provisions that are appropriate for harmonization with Russian rules and recommendations for the use of UV radiation. The article shows: the necessity of updating the Russian regulatory framework in the field of application of UV disinfection technology, the development of new or revision of existing documents by the bodies of the sanitary and epidemiological service of the Russian Federation in cooperation with competent technical organizations and specialists.

An alternative interpretation for tailing in survival curves for bacteria exposed to germicidal radiation.

It has been proposed that transient and reversible phenotypic changes could modify the response of bacteria to germicidal radiation, eventually leading to tailing in the survival curves. If this were the case, changes in susceptibility to radiation would reflect variations in gene expression and should only occur in cells in which gene expression is active. To obtain experimental evidence supporting the involvement of phenotypic changes in the origin of tailing, we studied changes in the susceptibility to radiation of cells able to survive high fluences, using split irradiations. Stationary phase cells of Enterobacter cloacae and Deinococcus radiodurans, in which gene expression is active, and spores of Bacillus subtilis, which are dormant cells without active gene expression, were used as microbial models. While cells of E. cloacae and D. radiodurans became susceptible after surviving exposures to high fluences, tolerant spores exhibited unchanged response to radiation. The results can be interpreted assuming that noise in gene expression modifies bacterial susceptibility to radiation, and tailing is the result of intrinsic phenomena of bacterial physiology rather than a technical artifact. For either theoretical or practical purposes, deviations from simple exponential decay kinetics should be considered in estimations of the effects of germicidal radiation at high fluences.

Ventilation Improvements Among K–12 Public School Districts — United States, August–December 2022

Improving ventilation has been one of several COVID-19 prevention strategies implemented by kindergarten through grade 12 (K-12) schools to stay open for safe in-person learning. Because transmission of SARS-CoV-2 occurs through inhalation of infectious viral particles, it is important to reduce the concentration of and exposure time to infectious aerosols (1-3). CDC examined reported ventilation improvement strategies among U.S. K-12 public school districts using telephone survey data collected during August-December 2022. Maintaining continuous airflow through school buildings during active hours was the most frequently reported strategy by school districts (50.7%); 33.9% of school districts reported replacement or upgrade of heating, ventilation, and air conditioning (HVAC) systems; 28.0% reported installation or use of in-room air cleaners with high-efficiency particulate air (HEPA) filters; and 8.2% reported installation of ultraviolet (UV) germicidal irradiation (UVGI) devices, which use UV light to kill airborne pathogens, including bacteria and viruses. School districts in National Center for Education Statistics (NCES) city locales, the West U.S. Census Bureau region, and those designated by U.S. Census Bureau Small Area Income Poverty Estimates (SAIPE) as high-poverty districts reported the highest percentages of HVAC system upgrades and HEPA-filtered in-room air cleaner use, although 28%-60% of all responses were unknown or missing. Federal funding remains available to school districts to support ventilation improvements. Public health departments can encourage K-12 school officials to use available funding to improve ventilation and help reduce transmission of respiratory diseases in K-12 settings.

Absorption of ultraviolet radiation in bacterial spores in clusters in air and on surfaces: Model calculations using the multi-sphere T-Matrix method

Ultraviolet (UV) germicidal irradiation (UVGI) is used to inactivate viruses and kill other microbes to decrease transmission of disease. Microbes such as bacterial spores can occur within clusters of spores or other particles. Such particles, in air or in water, can in some cases partially shield spores within them from UVGI, whether on a surface or suspended. There is a need to better understand how such shielding varies with particle size, composition, and illumination angle. Here the Multi-Sphere T-Matrix (MSTM) method is used to model the absorption of UVGI by bacterial spores in clusters, where each spore is approximated as a homogeneous sphere. The clusters of spores may be surrounded only by air or may be within an encompassing “host” sphere in air. Calculated results of the UV absorption efficiencies for each spore are illustrated for clusters of 54 spores within host spheres of different optical properties, on surfaces with different compositions (polycarbonate, iron and aluminum), and for illumination with UV light from different directions with respect to the cluster and the surface. For the solar UV wavelengths 302 and 325 nm and the deep purple 450 nm, and the unpigmented bacteria modeled here, the penetration depths in both the spores and host sphere are so much larger than the cluster and host sphere size (5.08 µm) that the general effect on the absorption by spores is relatively insensitive to wavelength. Results at 266 nm suggest that in using and validating UVGI for inactivation, the sizes and compositions of the particles are important.

Reduction in Operating Room Airborne Particle Burden and Time-Dependent Contamination of Sterile Instrument Trays With the Use of a Novel Air Filtration System.

IntroductionPostoperative infections represent a substantial burden to patients and healthcare systems. To improve patient care and reduce healthcare expenditures, interventions to reduce surgical infections must be employed. The crystalline C-band ultraviolet (UV-C) air filtration technology (Aerobiotix Inc., Miamisburg, OH, USA) has been designed to reduce airborne bioburden through high-quality filtration and germicidal irradiation. The purpose of this study was to assess the ability of a novel UV-C air filtration device to reduce airborne particle counts and contamination of surgical instrument trays in an operating room (OR) setting.Materials and methodsThirty sterile instrument trays were opened in a positive-air-flow OR. The trays were randomly assigned to one of two groups (UV-C or control, n=15 per group). In the UV-C group, the UV-C filtration device was used and in the control, it was not. All trays were opened with the use of a sterile technique and left exposed in the OR for four hours. Air was sampled by a particle counter to measure the numbers of 5µm and 10µm particles. Culture specimens were obtained from the trays to assess for bacterial contamination. Outcome data were collected at 30-minute intervals for the duration of the four-hour study period.ResultsUse of the UV-C device resulted in statistically significant reductions in the numbers of 5µm (average of 64.9% reduction when compared with the control, p<0.001) and 10µm (average of 65.7% reduction when compared with the control, p<0.001)-sized particles detectable in the OR. There was no significant difference in the overall rates of contamination (33.3% in the control group vs. 26.7% in the UV-C group, p=1.0) or the time to contamination (mean survival of 114 minutes in the control group vs. 105 minutes in the UV-C group, p=0.72) of surgical instrument trays with the use of the UV-C device.ConclusionsThe results demonstrate that the UV-C filtration device can successfully reduce airborne bioburden in standard ORs, suggesting that it may have the potential to reduce the risk for wound and hardware infections. Further clinical trials are necessary to better determine the effect of this air filtration system on postoperative infection rates.

Ultraviolet-C Light-emitting Device Against Microorganisms in Beauty Salons.

Background.Ultraviolet light in the UV-C band is also known as germicidal radiation, and it is widely used for decontamination and disinfection of environments, water, and food. The ultraviolet source transfers electromagnetic energy from a mercury arc lamp to an organism's genetic material. When UV radiation penetrates the cell wall of an organism, it destroys the cell's ability to reproduce, through a physical and not chemical process. Thus, the objective of this study was to evaluate the antimicrobial potential of a new UV-C generating device (Asepsis) against clinically important microorganisms that may be present in beauty centers.Methods.We present here a set of tests performed on tools easy to find in beauty salons (hair-brushes, nail pliers, makeup brushes, and, due to the recent COVID-19 pandemic, face mask samples). They were individually contaminated with bacteria (Pseudomonas aeruginosa, Staphylococcus aureus), fungi (Microsporum canis, Trichophyton rubrum, Candida albicans, Malassezia furfur), and the Chikungunya virus. Different times of exposure were evaluated (1, 3, and 5 minutes).Results.There was notable reduction in the microbial load in every test, in comparison with control groups. Best results were observed on face mask samples, while the makeup brush showed less reduction, even with longer periods of exposure.Conclusions.Beauty salons present a risk of infections due to microbial exposure. The device tested can efficiently inactivate, in a short time, microorganisms contaminating most tools found in this setting. The device also showed promising results against enveloped virus.

No Evidence of Induced Skin Cancer or Other Skin Abnormalities after Long-Term (66 week) Chronic Exposure to 222-nm Far-UVC Radiation.

Far-UVC radiation, typically defined as 200-235 nm, has similar or greater anti-microbial efficacy compared with conventional 254-nm germicidal radiation. In addition, biophysical considerations of the interaction of far-UVC with tissue, as well as multiple short-term safety studies in animal models and humans, suggest that far-UVC exposure may be safe for skin and eye tissue. Nevertheless, the potential for skin cancer after chronic long-term exposure to far-UVC has not been studied. Here, we assessed far-UVC induced carcinogenic skin changes and other pathological dermal abnormalities in 96 SKH-1 hairless mice of both sexes that were exposed to average daily dorsal skin doses of 400, 130 or 55 mJ cm-2 of 222 nm far-UVC radiation for 66 weeks, 5 days per week, 8 h per day, as well as similarly-treated unexposed controls. No evidence for increased skin cancer, abnormal skin growths or incidental skin pathology findings was observed in the far-UVC-exposed mice. In addition, there were no significant changes in morbidity or mortality. The findings from this study support the long-term safety of long-term chronic exposure to far-UVC radiation, and therefore its potential suitability as a practical anti-microbial approach to reduce airborne viral and bacterial loads in occupied indoor settings.

Capacity Models and Transmission Risk Mitigation: An Engineering Framework to Predict the Effect of Air Disinfection by Germicidal Ultraviolet Radiation.

A first-principles-based model for predicting the effect of germicidal radiation interventions for air disinfection is presented. Calculation of the "capacity" of an intervention expressed in volumetric flow rate allows for a direct comparison against fresh-air dilution ventilation and filtration systems, which are quantified in terms of the clean air provided. A closed-form expression to predict the combined quantitative impact of spatial gradients and mixing currents on the efficiency with which an intervention is applied is introduced. If validated, this would allow for systems to be selected and sized based on simple metrics across a broad range of settings and applications. The expressions developed are compared against available experimental data sets, and future validation efforts are proposed. Additionally, a method to identify an optimal operating capacity for a given setting by comparing costs associated with disease transmission against the cost of capacity is derived using the Wells-Riley equation and presented as an appendix.

Application of 233\xa0nm far-UVC LEDs for eradication of MRSA and MSSA and risk assessment on skin models

A newly developed UVC LED source with an emission wavelength of 233 nm was proved on bactericidal efficacy and skin tolerability. The bactericidal efficacy was qualitatively analysed using blood agar test. Subsequently, quantitative analyses were performed on germ carrier tests using the MRSA strain DSM11822, the MSSA strain DSM799, S. epidermidis DSM1798 with various soil loads. Additionally, the compatibility of the germicidal radiation doses on excised human skin and reconstructed human epidermis was proved. Cell viability, DNA damage and production of radicals were assessed in comparison to typical UVC radiation from discharge lamps (222 nm, 254 nm) and UVB (280–380 nm) radiation for clinical assessment. At a dose of 40 mJ/cm2, the 233 nm light source reduced the viable microorganisms by a log10 reduction (LR) of 5 log10 levels if no soil load was present. Mucin and protein containing soil loads diminished the effect to an LR of 1.5–3.3. A salt solution representing artificial sweat (pH 8.4) had only minor effects on the reduction. The viability of the skin models was not reduced and the DNA damage was far below the damage evoked by 0.1 UVB minimal erythema dose, which can be regarded as safe. Furthermore, the induced damage vanished after 24 h. Irradiation on four consecutive days also did not evoke DNA damage. The radical formation was far lower than 20 min outdoor visible light would cause, which is classified as low radical load and can be compensated by the antioxidant defence system.

Symmetrization and Amplification of Germicidal Radiation Flux Produced by a Mercury Amalgam UV Lamp in Cylindrical Cavity with Diffusely Reflective Walls

The study focused on increasing the efficiency of germicidal UV radiation by using highly diffuse reflective materials such as PTFE in irradiated cavities of UV air purifiers. In a conventional cylindrically symmetric cavity with a linear amalgam mercury lamp as UV-radiation source on the axis UV-radiation, flux directed from the lamp to the walls dropped from the axis to the periphery. To increase the UV irradiation, the walls are often made mirror-reflective, but the radiation flux distribution remained radially symmetric with a maximum on the source emitting surface in this case as well. When most of the emitted light is returned to the source after one reflection, the conditions of its operation are disturbed. If the walls are made of highly diffuse reflective materials, the radiation flux density inside the cavity increases on average, and its distribution becomes uniform and highly symmetric. Thus, the effect of amplification of the radiation flux due to the highly diffuse reflectivity of the walls increases with radius and reaches a maximum at the wall. Experiments were performed to demonstrate increasing amplification of germicidal UV radiation flux with a diffuse reflection coefficient in cylindrical cavities with walls of PTFE and ePTFE. The irradiation of the cavity wall was observed to increase up to 20 times at the resonant mercury line of 253.7 nm and up to 40 times at some non-resonant lines of the visible range due to highly diffuse reflectivity of the cavity walls. The flux amplification effect was limited by the diffuse reflectivity value of the walls and absorption coefficient of the radiation emitting surface. A formula for calculating the radiation flux amplification factor in a diffusely reflecting cylindrically symmetric cavity was derived for the case of Lambertian source and reflector, including wall reflectivity and source surface absorption coefficients. The effects of heating and cooling of the mercury lamp amalgam directly affected the amplification, and symmetrization of germicidal irradiation was observed and is discussed in the paper. Numerical calculations were performed by the ray tracing method. The calculated model was verified by comparing the numerical results with those of both the approximate theoretical consideration and experiments. The promising use of diffusely reflecting cylindrical cavities for UV air purifiers is discussed. Designs of air inlet and outlet ports that allow effective locking of germicidal radiation inside the UV air purifiers were considered. The results of this work may be of interest for further developments in the UV disinfection technique.

Development of a novel self-sanitizing mask prototype to combat the spread of infectious disease and reduce unnecessary waste

With the spread of COVID-19, significant emphasis has been placed on mitigation techniques such as mask wearing to slow infectious disease transmission. Widespread use of face coverings has revealed challenges such as mask contamination and waste, presenting an opportunity to improve the current technologies. In response, we have developed the Auto-sanitizing Retractable Mask Optimized for Reusability (ARMOR). ARMOR is a novel, reusable face covering that can be quickly disinfected using an array of ultraviolet C lamps contained within a wearable case. A nanomembrane UVC sensor was used to quantify the intensity of germicidal radiation at 18 different locations on the face covering and determine the necessary exposure time to inactivate SARS-CoV-2 in addition to other viruses and bacteria. After experimentation, it was found that ARMOR successfully provided germicidal radiation to all areas of the mask and will inactivate SARS-CoV-2 in approximately 180 s, H1N1 Influenza in 130 s, and Mycobacterium tuberculosis in 113 s, proving that this design is effective at eliminating a variety of pathogens and can serve as an alternative to traditional waste-producing disposable face masks. The accessibility, ease of use, and speed of sanitization supports the wide application of ARMOR in both clinical and public settings.

Deep-UV wavelength-selective photodetectors based on lateral transport in AlGaN/AlN quantum well and dot-in-well structures

We report on the development of deep-ultraviolet (DUV) wavelength-selective top-illuminated photodetectors based on AlGaN/AlN quantum-dots-in-wells. Structures consisting of 100 AlGaN wells and AlN barriers were grown by plasma-assisted molecular beam epitaxy on sapphire substrates. Interdigitated metal–semiconductor–metal photodetector devices were formed lithographically using indium as the contact metal. The effect of variation of the group III to group V flux ratio and the use of indium as a surfactant on the UV photoresponse were determined. Growth under near-stoichiometric conditions lead to a photocurrent peak in the 210–215 nm range with a peak width of ∼20 nm, with no other additional signatures in the entire UV–visible range. Under excess group III conditions, a second red-shifted peak was observed at ∼225 nm with significantly (up to 10×) higher responsivity. This enhancement was linked to the formation of quantum dots with truncated pyramidal structures with near-uniform size distribution and density of 6 × 1010 cm−2 within the quantum wells. Their formation was attributed to the process of droplet epitaxy. Such photodetectors do not require p-type doping or growth onto UV-transparent substrates and are appropriate for monitoring DUV skin-safe germicidal radiation in the presence of ambient visible light.

Light, lighting and human health

Light can impact human health via the visual and non-visual systems originating in the retina of the eye or as optical radiation falling on eye or skin. This paper provides a summary of what is known about these impacts. Topics covered include aspects of lighting likely to cause eyestrain and headaches; increase the risk of falls; induce circadian disruption; enhance sleep; mitigate Alzheimer’s disease and depression; produce tissue damage; alleviate diseases through phototherapy and inactivate viruses through germicidal irradiation. It is concluded that human health is undoubtedly influenced by lighting, but there are four conditions that should be attached to such a simple assertion. First, the impact of lighting on human health can be either positive or negative. Second, human health is affected by many factors other than lighting. Third, the severity of the effects of light exposure can vary widely from the short-lived and trivial to the long-term and fatal. Fourth, the same lighting conditions can have very different health impacts for different individuals depending on their age and medical status. Taken together, these conditions imply that care is required when judging the veracity and relevance of broad assertions about the benefits of lighting for human health.

Dose fractionation as a promising strategy to improve UV disinfection

Survival curves for bacteria exposed to germicidal radiation (254 nm) usually exhibit a decreased slope at high doses, because bacterial populations contain a small proportion of cells able to tolerate the effects of the radiation. These cells could survive due to external shielding by aggregation or association with inert particles. However, it has been proposed that transient and reversible phenotypic changes modifying UV susceptibility also occur and lead to a phenomenon of persistence. Using Escherichia coli as a model organism, and comparing the effects of continuous exposures to those of irradiations separated by incubations in the dark, we found that in most of the survivors to high UV doses, the condition conferring tolerance (possibly self-aggregation) is transient and reversible, as would be expected in a persistent sub-population. Splitting the irradiations into two exposures reduced viable counts to the detection limit (6.32 orders of magnitude) under conditions in which continuous irradiations produced a reduction no greater than 4 orders of magnitude. In those processes where it is feasible, UV dose fractionation could improve the effectiveness of disinfection by ultraviolet radiation.

Does Prolonged Exposure of Environmental Fungi to Ultraviolet Irradiation Change the Pattern of Drug Resistance?

Background: The pathogenic and opportunistic fungal species cause life-threatening infections in immunocompromised patients. The ultraviolet (UV) germicidal irradiation is a well-known method for inactivating a significant number of microorganisms and has wide application for sterilization. Objectives: This study aimed to investigate the effect of ultraviolet C (UV-C) irradiation on the antifungal susceptibility pattern of some filamentous fungi. Methods: The effect of UV-C on the antifungal susceptibility pattern of itraconazole, voriconazole, fluconazole, and amphotericin B against filamentous fungi was examined. Changes in the morphological features of resistant strains following UV-C irradiation were also evaluated using scanning electron microscopy. Results: The results revealed a significant decrease in the number of the surviving spores of strains with the prolongation of UV-C irradiation (0 - 10 to 20 min; P &lt; 0.05). Concerning the morphology of resistant Aspergillus spp., the results of scanning electron microscopy showed a significant increase in the length of irradiated hyphae compared to the non-irradiated hyphae (P &lt; 0.05). In addition, colony count showed a significant decrease (P &lt; 0.05). The findings revealed that UV-C radiation exposure could alter the antifungal susceptibility pattern of Aspergillus spp., such as increasing the minimum inhibitory concentration. Conclusions: Aspergillus spp. can cause systemic infections among lab technicians exposed to different doses of radiation. Moreover, this increase in susceptibility pattern can directly affect the duration of treatment.

Air Disinfection by UV Germicidal Radiation

Since 2005, in our country, the use of UV germicidal radiation for disinfection of the indoor air environment is regulated by the guidance of R3.5.1904–64 (as the recommendations). This radiation is dangerous for humans: skin and especially the eyes are affected. It is necessary to use closed irradiators (recirculators) with germicidal lamps, and not open ones, the radiation of which covers the entire volume of the room in order to avoid exposure of people during disinfection of indoor air. This requires taking people from the premises and observing all relevant safety measures. Unfortunately, in practice, there may occur, accidentally or out of ignorance of the rules for open irradiators operating by personnel, violations of safety rules leading to grave consequences. To eliminate such violations, it is necessary to increase the level of knowledge of staff, but there is no special educational and technical literature. This article attempts to fill this gap.

Reducing Clostridium difficile Infection Among Hematology-Oncology Patients Using Ultraviolet Germicidal Irradiation for Terminal Room Disinfection

Setting: Three adult hematology-oncology units with a total of 75 private and 7 semiprivate rooms in a 695bed tertiary care hospital. UVGI deployment:  Targeted CDI or contact precautions rooms for UVGI using an electronic patient flow system (NaviCare, Hill-Rom).  Following terminal room cleaning with bleach, UVGI (Optimum-UV, Clorox Healthcare) was deployed for two 8-minute cycles on either side of the patient bed with the bathroom door left open.  Two UVGI units and no additional Environmental Service personnel or resources were utilized for this evaluation. Measurements:  C. difficile detected by toxin A/B and GDH immunoassay; indeterminate results confirmed by PCR for toxin gene; NHSN GIT definition.  Compared rates of healthcare onset CDI on study units and non-study units:  Baseline period (P1, Jan.-Dec. 2013) vs. Intervention period (P2, Feb. 2014-Jan. 2015)  Calculated rate ratios and a mixed-effects Poisson regression model with random effects for unit and time in months. Background: •Clostridium difficile forms spores that are resistant to many disinfectants and can persist in the hospital environment for months. • During 2013 (baseline period, Jan.-Dec. 2013), there were 87 cases of hospital onset C. difficile infection (CDI) among patients on three Hematology/Oncology units—a rate 5 times higher than that for all other inpatient units combined. • Cases of CDI continued to occur despite targeted evidence-based interventions and EVS process improvements, including use of bleach for daily and terminal room cleaning of CDI rooms, process monitoring and feedback of cleaning effectiveness. • We performed a 12-month pre/post evaluation of terminal room disinfection using ultraviolet wavelength C germicidal irradiation (UVGI) on C. difficile infection (CDI) rates and room turn-around. Process Improvement: Weekly reporting of UVGI deployment and room cleaning metrics Redeployment of additional Environmental Services associates to second shift (3-11 pm) and cross-training to improve UVGI deployment during peak discharge times. Deployment of a second UVGI unit during Sep. 2014. Feedback and recognition of associates deploying UVGI.

Environmental control of tuberculosis

The premise of this article is that it is possible to reduce but not eliminate the risk of TB infection in many institutional settings through environmental interventions--as supplements to conventional public health TB control efforts. Of the environmental means available to reduce the concentration of infectious droplet nuclei, ventilation, isolation strategies, and personal respirators have received the most attention, but each has inherent limitations. Ventilation and other air-moving strategies (i.e., fan-filter and fan-UV room units) are limited by the large volume of air that must be moved to dilute and remove already dilute droplet nuclei. Isolation assumes that potential transmitters are suspected, whereas negative pressure in isolation rooms is difficult to achieve and maintain in many hospitals. The use of well-designed small enclosures for sputum induction and other high-risk procedures, however, should provide highly effective source control. Personal respirators have a limited protective role because they cannot be worn by all workers at all times, and cannot reasonably be issued to other patients and visitors. Germicidal UV irradiation of upper room air is widely misunderstood, but offers practical air disinfection that can be safely and efficiently deployed in a variety of high-risk environments. Although there are theoretical and experimental bases for these recommendations, there are no clinical field trials preventing TB using any of the available environmental interventions, primarily because of the highly variable nature of TB transmission.