Abstract: At approximately 8:00 a.m. on March 14, 1989, Employee #1 and his foreman entered a 12 ft wide by 43 ft long by 13 ft deep trench to check a joint on a 24 in. ductile iron water line pipe that had been laid the previous day. They were protected by a trench box. The pipe section had been maneuvered around that morning to get it in the proper alignment with the pipe section toward which it was heading. Employee #1 crawled 20 ft inside the pipe to check that the gasket between the new section and the pipe to which it was connected had not been pushed out by the shifting of the pipe. When Employee #1 reached the gasket, he struck a match to see what he was doing, resulting in a spontaneous explosion and flash fire from the flammable gases that had accumulated inside the pipe overnight. He sustained second-degree burns to his hands, face, and neck. Causal factors related to this accident were the lack of training on confined space entry procedures and the employee's failure to monitor the air quality inside the pipe prior to entry.