Abstract: On October 2, 2000, Employee #1 and a coworker were retubing a 194-tube, natural gas-fired, three-pass boiler for general maintenance. Employee #1 was standing in the boiler's firebox as they checked for leaks. The water level within the tubes rose enough to automatically reset the low water fuel-cutouts, which initiated burner ignition. Employee #1 sustained second-degree burns to his face, ears, and chest before exiting the firebox at the front of the boiler. He was transported to the hospital, where he was treated and released. Neither the electrical nor the gas supply to the boiler/burner had been isolated and locked out before work began on the boiler two weeks before the accident. The employer did not use appropriate confined space procedures or obtain the required permit for work in such spaces.