Experimental study on displacement and mixing ventilation systems for a patient ward

In hospital patient wards, exhalation flow from patients with airborne infectious diseases can impose health risks to caretakers and visitors. Usually, mixing ventilation is used to remove airborne contaminants, but displacement ventilation is becoming a popular alternative. This study investigated experimentally the performance of both mixing and displacement ventilation by using a full-scale environmental chamber to simulate a one-person patient ward. Results show that displacement ventilation may or may not provide a better air quality in the ward, depending on the location of the exhaust in relation to the restroom. A tracer gas (SF₆) and 1 or 3 μm particles can be used to simulate contaminants breathed out by a patient. These contaminants generate similar contaminant distributions in the ward, except in the areas close to the contaminant source and the exhaust adjacent to the restroom, where the flow may be unstable. The experimental data obtained from this study can be used to validate the computational fluid dynamics (CFD) models.