This project requires transporting LNG from coastal LNG carriers to onshore storage tanks via pipelines that traverse mountain tunnels under extremely harsh environmental conditions. Confined tunnel spaces and numerous interfering factors led to insufficient accuracy, frequent false alarms and missed detections in the electrochemical and infrared monitoring devices initially put into operation, which failed to meet the safety monitoring requirements for hazardous gas leakage. Against this backdrop, the project owner introduced the Hanhai Passive Laser Leakage Monitoring System in December 2021. Boasting core advantages of strong anti-interference capability, high monitoring precision and wide coverage range, this system accurately addressed the challenges posed by the harsh tunnel environment, completely resolved the core problem of gas monitoring in tunnel sections, built a solid defense for the safe and stable transmission of LNG, and earned high recognition from the project owner.