Methods to Reduce Transmission of Airborne Viruses in a Bus Cabin

Public buses can be high-risk environments for the transmission of airborne viruses due to the confined space and high passenger density. However, advanced cabin air control systems and other measures can mitigate this risk. This research was conducted to explore various strategies aimed at reducing airborne particle transmission in bus cabins by using retrofit accessories and a redesigned parallel ventilation system. Public transit buses were used for stationary and on-road testing. Air exchange rates (ACH) were calculated using CO₂ gas decay rates measured by low-cost sensors throughout each cabin. An aerosol generator (AG) was placed at various locations inside the bus and particle concentrations were measured for various experiments and ventilation configurations. The use of two standalone HEPA air filters lowered overall concentrations of particles inside the bus cabin by a factor of three. The effect of using plastic “barriers” independently showed faster particle arrival times of 2–3 min and reduced particles concentrations by 20% compared to the baseline maximum concentration. The parallel system is 80% more effective in the removal of particles inside the bus cabin when compared to the conventional system. Installation of barriers makes the parallel system 70% more effective than the conventional system with barriers. Finally, filter efficiencies for new Minimum Efficiency Reporting Value (MERV) 13 filters were found to be higher than the pre-existing filters in the bus cabins due to electrostatic charge effect.