Potential of a bed ventilation system in reducing the risk of exposure to contaminants in infectious wards

A proposed bed ventilation system named Hospital Bed Integrated Ventilation Cleansing Unit (HBIVCU) has shown its great potential in reducing the risk of airborne cross -infection. However, the key operating parameters are still unclear, restricting its practical application. This study numerically investigated the performance of the HBIVCU under various operating parameters (supply and exhaust airflow rates increased from 0 L/s to 5 L/s and 0 L/s to 40 L/s, respectively) in a four-bed infectious ward with different background ventilation rates. Both tracer gas CO2, (simulating aerosols smaller than 5 mu m) and particles (mean diameter of 80 mu m) in the exhaled by one of the patients were considered. Compared to the ward without the HBIVCU, the concentration of CO2 at the bed microenvironment and breathing height of standing and sitting persons are reduced by more than half when the HBIVCU operates with supply and exhaust airflow rates of 5 L/s and 40 L/s, respectively. For this case, the highest draught risk of 13% at the patients' head region is obtained. Increasing the supply and exhaust airflow rates of the HBIVCU are both helpful for removing the exhaled gaseous contaminants from the room due to increased induction effect of the local bed ventilation flow. The removal efficiency is around twice higher when the HBIVCU is operating at background ventilation at 6 air changes per hour (ACH) when compared to when it is not operating at background ventilation of 12 ACH. Finally, the HBIVCU can efficiently remove the exhaled gaseous contaminants, though it has no discernible effect on the removal of coughing droplets. The HBIVCU has great potential to reduce the risk of crossinfection and save energy by lowering the background ventilation rate.