The distribution of supply air determines the resulting air velocities, temperatures, and concentration of contaminants in a patient room. This inturn determines thermal comfort and potential for transmission of airborne infectious pathogens in a patient room. Several interrelated factors canaffect the performance of air distribution systems including the location and type of supply air diffusers, location and size of return air grills, andlocation and strength of various heat sources.

This paper with the help of Computational Fluid Dynamics (CFD) analyses describes the impact of various locations of supply air diffusers and return air grill on the airflow patterns, temperature distribution, resulting thermal comfort of occupants, and on the probable flow path of airborne pathogens in a patient room. These analyses indicate linear diffusers can cause strong recirculation and entrainment (induction) flows in the room. Depending on the location of the return grill the airborne pathogens released from the patient's face can get entrained back into the supply air stream and can eventually spread into the entire room. Placing the return grill behind the linear supply diffuser over the patient's head showed most promising results in reducing the entrainment of airborne pathogens back into the supply stream. It is noted that CFD can be an effective tool for analyzing and optimizing the design of air distribution systems to obtain the desired combination of occupant thermal comfort and the best possible hygienic conditions in patient rooms.