The airborne transmission of pathogens including tuberculosis and influenza pose a significant threat to human health. This is especially the case in healthcare settings such as hospital wards which inevitably contain a high concentration of viruses and bacteria. These have the potential to infect both patients with weakened immune systems and healthcare workers. In order to reduce the infection risk, improvements in hospital ward design and the application of disinfection systems can offer significant benefits. One such strategy, upper-room Ultraviolet Germicidal Irradiation (UVGI), relies on a collimated irradiance field which works in conjunction with ventilation patterns to disinfect the air. The focus of this study is to predict the UVGI system performance within a naturally ventilated hospital ward, for a range of ambient conditions using Computational Fluid Dynamics (CFD). A computer model of an open-plan six-bed Nightingale-style hospital ward was generated based on the dimensions of a former hospital building situated in Bradford, UK. With a total volume of 200 m3, natural ventilation is supplied through three casement windows and a further three openings on the leeward side ensure steady cross-ventilation. Boundary conditions are based on experimental measurements of the ventilation rate which were determined using a tracer technique. An experimentally-determined irradiance field is included in the model and stored as a fixed-value scalar field. A total of fifty steady-state CFD simulations show that disinfection performance depends on the ventilation rate, the degree of mixing present and the position of the UVGI fixture within the ward. The results underline the potential performance gains from UVGI installations and how they could be integrated within existing healthcare facilities as an infection control measure
