Dear Editor-in-Chief According to the advance of civil engineering and transportation, the tunnel tends to increase as a number and be longer as a scale. It is divided to underground and undersea tunnel by location, and is sorted into railway and road tunnel by transportation. Channel Tunnel is world’s longest undersea railway tunnel that reaches a length of 50.45 km. Great Britain is connected to France by it. The longest tunnel in Korea is Geumjung Tunnel that is 20.3 km for express rail. The tunnel is built recently adapts high-tech equipments like ventilation, evacuation, fire prevention, and monitor system.