…air conditioning systems in cars are typically designed to optimize the comfort of the occupants, not reducing airborne disease transmission,
CONCLUSIONS
We have performed a computational study employing Reynolds-averaged Navier–Stokes (RANS) simulations to investigate the overall flow fields and aerosol transmission patterns in a passenger car, extending the recent work by Mathai et al. to a wider variety of practically relevant driving scenarios. Although the key conclusions are still somewhat expected—more ventilation means lower aerosol concentrations and lower pathogenic transmission risks—there are nevertheless several less-obvious conclusions to be drawn. We have identified that when driving at high speeds (50 miles per hour or 22 m/s), partially opening windows might be sufficient to remove potentially pathogenic airborne particles from the cabin. This provides a practical compromise when having to drive under poor weather conditions. Additionally, our analysis has shown the utility of opening the moonroof on vehicles while driving, as it serves as an unimpeded exit for the contaminated cabin air. The results also emphasize a point made by Mathai et al. that the microclimate—the distribution of aerosols within the cabin—is as important as the more integral measures of ventilation, such as the air changes per hour (ACH) when considering the occupants' health risks.
