Multizone modeling of strategies to reduce the spread of airborne infectious agents in healthcare facilities

Control of airborne infectious agents in hospitals is critical both to effective healthcare and to the control of direct and indirect health care costs. Current hospital design guidelines focus on ventilation rates, room pressure control and air filtration to control the spread of airborne infectious agents. Studies indicate, however, that there is much variability in hospital design strategies used by engineers to control airborne pathogens. This study focuses on a number of questions concerning current hospital design practices and provides an overview of the tools and methods that can be used to answer some of these questions. Multizone airflow and contaminant transport simulations are used to examine different control strategies and some related issues of design and application. Design issues associated with room pressurization, filtration, and ultraviolet germicidal irradiation (UVGI) are also reviewed. The results provide some important insights into the following issues: 1) using a ventilation flow differential based on building leakage better captures the relevant airflow physics of space pressure control; 2) anterooms can be effective barriers for reducing contaminant transport due to pressure differential disruptions; and, 3) filtration can provide significant protection, with more effective protection provided by additional UVGI systems.