CFD based airflow modelling to investigate the effectiveness of control methods intended to prevent the transmission of airborne organisms.

The airborne transmission of disease is a constant threat and while diseases such as Tuberculosis were considered all but extinct in the western world, the resurgence of it demonstrates that the spread of these diseases has to be taken very seriously. This paper describes the method of application of Computational Fluid Dynamics (CFD), more appropriately called Airflow Modelling for the Building Services Industry, to the airflow and heat transfer in a Hospital Isolation Room Application. In particular it addresses how it can determine the ability of the ventilation system to limit the time during which carers, or other people present in the room, may be at risk to the airborne organisms constantly being produced by a patient coughing, sneezing or simply talking. Research has shown that ventilation rate is no guarantee of control of these airborne organisms. Another means of minimising the risk from airborne bacteria is to apply ultraviolet germicidal irradiation (UVGI). UVGI holds promise of greatly lowering the concentration of airborne bacteria and thus controlling the spread of airborne infection among occupants. This paper describes the techniques developed to allow the airflow simulation to be extended to simulate the motion of the droplets carrying the bacteria, their path through the room and indeed any exposure they may have to UVGI. The work will be highlighted by a series of case studies demonstrating the effect of change in the ventilation design and the effect of UVGI on the probability of survival of the bacteria.