Abstract
Ultrafine particle number concentrations are measured at five stations and inside trains on four routes in the Taipei Rapid Transit System during OctoberûDecember 2007. The results indicate that there are no additional emission sources of ultrafine particle on the platforms. Ultrafine particle levels at a ground level station were, however, adversely affected by traffic outside of the station. Moreover, particles can enter the underground stations via the subway tunnels resulting in high levels during weekdays. (A) Reprinted with permission from Elsevier.