During excavation of Shilin headwaters tunnel, there was a serious gas escape and gas explosion which caused the deaths of two people. The problem was rock slips had allowed gas to escape. The owners had contacted a number of international professional firms. They finally adopted our company’s proposal to provide gas-sealing polyurethane resin grouting as the way forward while excavating. After the rock plate resin grouting treatment, the amount of gas escaping could be effectively controlled and tunnel boring could be continued to completion. This project was the first case of using polyurethane resin grouting for gas sealing in Taiwan.