2022 Yes https://doi.org/10.1080/15459624.2022.2050739 Van Dyke, Michael North America Exposure Study Other Ventilation rates Carbon Dioxide (CO2) Air change rate (ACH/AER) COVID-19 Transmission School bus Tracer gas CO₂ tracer decay method was used to measure air change rates under different ventilation configurations in school buses. Highest ACH achieved with windows and hatches open. Findings guide practical airborne infection mitigation during student transport.