Development of Computational Models to Design Upper-Room Ultraviolet Germicidal Irradiation Air Disinfection Systems in Hospital Environments

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Ultraviolet Germicidal Irradiation (UVGI) irradiation has been known for many years to have a lethal effect on microorganisms. It is routinely used in water disinfection and can be a viable method of reducing airborne pathogens in indoor environments to decrease the risk of cross transmission of infection. Despite recommendations for use in high risk healthcare environments such as tuberculosis (TB) wards, the application of UVGI remains limited due to lack of evidence gained directly in clinical settings. However two major clinical studies that are about to be published will prove the effectiveness of UVGI devices against TB transmission and thus a significant increase in the future demand for UVGI air disinfection is anticipated. To translate these clinical based research findings into successful control strategies tailored to the needs of a particular healthcare environment, robust guidance on designing safe and effective UVGI air disinfection systems is now needed. This project aims to address this need by developing a design tool for simulating the behaviour of upper room air disinfection devices in realistic hospital environments, and guidance documents to enable hospital managers, architects and engineers to (a) determine if UVGI disinfection is suitable for a particular environment and (b) to ensure any UVGI installations are both effective and safe. The proposed study will use computational fluid dynamics (CFD) simulations to carry out a parametric study quantifying the factors that influence the performance of a UV device to produce an empirical model of UVGI disinfection within a ventilation design model. The model will quantify the mean effectiveness, as well as stochastic variations, and provide an output in terms of UV device performance and relative risk of infection for ward occupants. This will enable better design and specification of UVGI systems without the use of resource intensive CFD models. Parametric studies using CFD models and the new design tool will then be used to draft three design guidance documents; suitability of upper-room UVGI systems in healthcare environments, safe installation and operation of UVGI systems, and optimising UVGI system design to minimise airborne infection risk.