International travelling is growing rapidly, increasing the risk of spreading airborne infectious diseases such as influenza or SARS. In case of pandemic outbreaks, the demand for airborne infection isolation rooms (AIIRs) can be urgent. The challenge today is that there is only a limited number of AIIRs in each hospital. The rooms are expensive to build and airflow control to avoid contamination is often complicated.
Computational Fluid Dynamics (CFD) simulations have been performed to study the air flow patterns in an AIIR. The results are compared with laboratory experiments in a full-scale test chamber. The results from the baseline cases, consisting of a normal bed ward with balanced ventilation, showed that door opening and exiting the patient room can lead to an air transfer of up to 781 L (27.6 ft3) of potentially contaminated air. This means that high air exchange rates and long waiting time are necessary to dilute the air in the anteroom before the health care worker can exit the AIIR.
Instead of high air exchange rates and emphasis on the dilution of air, this paper proposes a design for simplified AIIRs that focuses on air flow patterns and air movement. Results from CFD simulations and laboratory experiments of the simplified solution show that installing a ventilation unit that supplies a high air volume into the anteroom through low velocity wall diffusers, significantly reduces the air escaping the patient room during door operation. 300 L/s (10.6 ft3/s) of diffuse air reduced the air transfer due to door opening and passange by 72-75 %. 500 L/s (10.6 ft3/s) diffuse air flow resulted in an 80-86% reduction, while 1000 L/s (35.3 ft3) gave an 85-96% reduction compared to the baseline cases. The results show that the ventilation unit can significantly reduce the amount of contaminated air that escapes from the patient room for a fraction of the cost compared to a normal AIIR. This will enable hospitals and other healthcare facilities to be better prepared for future pandemics, and also meet the current challenges to limit the spread of airborne diseases.