Natural personalised ventilation: a novel approach

The need to protect susceptible patients from cross-infection resulting from airborne pathogens is essential in hospitals, especially when patient immunity is either suppressed due to medical procedures or compromised by ailment. Personalised ventilation (PV) is a method of creating a local zone of high air quality around such patients. However, contemporary PV techniques are based on mechanical ventilation, which adds to the energy burden of healthcare buildings. In single-bed wards, a potential source of infection could be other occupants such as visitors and healthcare workers. Threats may also come from airborne pathogens migrating from adjacent zones, especially if the single-bed wards in question are not positively pressurised. While the World Health Organisation (WHO) has issued guidelines on using natural ventilation to control infectious bio-aerosols in hospital wards (with flow rates of up to 60 l/s/patient), how to achieve this rate without high energy and carbon costs, remains unanswered. The objective of the research reported here is to demonstrate a novel approach of using low-energy, buoyancy-driven natural airflow for personalised ventilation of single-bed hospital wards. The investigation has been carried out by undertaking dynamic thermal simulations (DTS) and computational fluid dynamics (CFD) simulations. Findings demonstrate that given appropriate design, it is possible to achieve personal protection for vulnerable patients using a natural mode of ventilation alone. Co-occupants could also benefit from the mixing characteristics offered by the proposed system, which does not occur in typical buoyancy-driven displacement ventilation.