Using computational fluid dynamics (CFD), this study simulated the air supply and exhaust conditions inside KTXSancheon train cabin to analyze the airflow, velocity, temperature, and residence time distributions. Based on the analyzed airflow in the cabin, the trajectory properties of droplets with various diameters exhaled from a passenger in a specific seat were analyzed. In the train cabin, forced airflow was formed by the operation of an air conditioning unit, while air stagnation occurred through spinning vortices at the front and rear where there were no floor outlets. Droplet particles ≤36 μm in diameter were dispersed throughout the cabin following the airflow generated by the air conditioning unit. The degree of dispersion differed according to the passenger seat location. In addition, the expelled droplets were mostly deposited on the surfaces of passenger bodies, seats, and floor. The ratio of deposited droplets to suspended droplets was increased with increasing droplet size. Further, the CFD study allowed the prediction of the possibility of exposure to exhaled droplets by estimating the dispersion and deposition properties of droplets released from a passenger in a specific seat. This study can be utilized to adjust the operation of air conditioning units and encourage the installation of air-purifying units to minimize secondary infections.

This paper is focused on an economic analysis of applied air pollutant control technologies used for the particulate matters present in subway. Beneficial effects such as reduction in medical expenses and prevention of productivity loss and death are achievable through the adaptation of control technologies. The result showed that the total investment expense was 97.6 billion won and the cost-benefit was 4776.8 billion won, therefore a 4.8 benefit/ cost ratio was attained.

This study characterized PM and VOC emissions from cow dung combustion in a controlled experiment. Dung from grass-fed cows was dried and combusted using a dual cone calorimeter. Heat fluxes of 10, 25, and 50 kW/m² were applied. The concentrations of PM and VOCs were determined using a dust spectrometer and gas chromatography/mass spectrometry, respectively. PM and VOC emission factors were much higher for the lower heat flux, implying a fire ignition stage. When the heat flux was 50 kW/m², the CO₂ emission factor was highest and the PM and VOC emission factors were lowest. Particle concentrations were highest in the 0.23-0.3-μm size range at heat fluxes of 25 kW/m² and 50 kW/m². Various toxic VOCs including acetone, methyl ethyl ketone, benzene, and toluene were detected at high concentrations. Although PM and VOC emission factors at 50 kW/m² were lower, they were high enough to cause extremely high indoor air pollution. The characteristics of PM and VOC emissions from cow dung combustion indicated potential health effects of indoor air pollution in developing countries.