Application of a Two-stage Brush-type Electrostatic Precipitator for Particulate Matter Removal in a Subway Tunnel

As passengers spend more time in underground spaces, and as their numbers grow, the air quality within underground subway stations is deteriorating. In particular, the concentration of particulate matter (PM) is increasing in most underground subway systems worldwide. These airborne particulates are continuously generated due to friction wear of brake pads and wheels during train operation. To tackle this issue, ventilation systems have been implemented. However, the air quality in underground subways may worsen further when the outdoor air quality is worse. To mitigate this problem, we applied a two-state brush-type electrostatic precipitator for supplying and exhausting clean air from the subway station. As a result, more than 50% of the incoming outdoor air is purified before entering the subway tunnel, allowing a reduction of over 20% in PM2.5 concentration within the tunnel. Additionally, the concentration of particulate matter emitted to the outside environment was reduced by more than 50%. This study demonstrates the direct reduction of particulate matter within subway tunnels and highlights the added benefit of improving both underground and outdoor air quality.