Study on the Indoor Air Quality of Seoul Metropolitan Subway during the Rush Hour

With increasing interest in indoor air quality (IAQ), the recommended standards for the IAQ of public transportation were established in 2003 in Hong Kong and in 2007 in Korea. According to the recommended standards on the IAQ of public transportation of both Hong Kong and Korea, the air quality in the passenger cabins of railway vehicles may be improved through the ventilation system using outside air. Also, it is reasonable to use the carbon dioxide (CO2) level as the index of improvement. The Korean guidelines on the air quality in cabins include the recommended standard for particulate matter <10 μm (PM10) as well as CO2. In this study, the levels of CO2 and PM10 were continuously measured in the subways operated in the Seoul metropolitan area and the number of passengers using subway vehicles was surveyed based on the lines in operation and each stopping station. In addition to CO2 and PM10 levels, the temperature and moisture (RH%) in the passenger cabins were also measured. The average CO2 and PM10 levels for each line were compared with the recommended levels of cabin air quality. The correlation analysis to the number of passengers proved that the CO2 level was linearly correlated with the number of passengers. The average CO2 level and PM10 level in the subway trains in the metropolitan area were found to be below that recommended in the air quality standards for cabins.