Does the disturbance caused by moving objects matter in air quality in an inpatient ward with displacement ventilation

Moving objects can disturb stratified flow and contaminant concentration gradient in an inpatient ward with displacement ventilation. This investigation used Computational Fluid Dynamics (CFD) to study the effect of moving objects, such as a walking visitor and caretaker on the contaminant concentration distributions in a single inpatient ward. The contaminant was assumed to be breathed out by the patient lying on the bed. The results show that the concentrations returned to steady state level in approximately 90 s after the movement stopped. The averaged concentration change at the breathing levels in the ward was generally less than 25%, so the risk level should remain the same. The closer the location of the moving object to the contaminant source, the larger was the change in the contaminant concentration. The displacement ventilation with 4 ach in an inpatient ward with a moving object can produce the same air quality level as overhead mixing ventilation with 6 ach.