Indoor environmental quality and pollutant dispersion estimation inside a bus at the downtown areas of Dalian, China

Among most public transport modes, the frequent start-stop urban bus has the most complex micro-environment. Indoor environment quality, airflow patterns, etc. has not been fully understood yet inside buses. In addition, under COVID-19 pandemic, it had been proved aerosol transmission risk might be enhanced inside the buses. Usually, carbon dioxide (CO2) could be considered the index of ventilation effect in enclosed environment, airborne particles are viral carriers. Thus, accurate forecasting of the two abovementioned key pollutants become important. The study analysed the CO2 and airborne particle dispersion inside a bus at the downtown areas of Dalian, China by employing field measurement at spring and autumn, 2021. Temperature, relative humidity, CO2 and airborne particle concentrations were logged by sensors at sampling points respectively, passengers onboard were counted manually. Correlation analysis was conducted and two empirical models for evaluating CO2 and airborne particle were concluded based on the measurement data. From preliminary results, transient concentration of pollutant is almost linearly correlated with cumulative and instant numbers of passenger respectively, with Pearson correlation coefficient larger than 0.8336 for CO2 and 0.8424 for PM2.5. The purpose of the study is to reflect environmental quality inside the bus and provide inspiration into pollution control strategies in buses.