We introduced our identical systems, which were installed at three S. Korea stations, using CRDS and a drying system. The measurement uncertainty was ~ 0.11 ppm across the stations. CO₂ observed in the west of S. Korea was very sensitive to East Asia (e.g., China), indicating that data include CO₂ flux information from East Asia. Through long-term comparison to other East Asian stations, it was suggested that they could be affected not only by local vegetation but also by measurement quality.