Abstract: An employee was working for a contractor that supported gas and oil operations. On or before December 21, 2021, a leak was found on a flange for a bypass line on the Hydro Desulfurization Unit (HDU-1) at refinery operated by an international oil company. The leak was detected because the leak had auto ignited. The refinery owner's fire team had been called out to put the fire out. After the fire was out, steam lances were continuously directed on the flange due to the potential of another flash fire from the leaking heated naphtha. The refinery's owner hired two contract companies to repair the leaking flange using a method called hot bolting. In this method, one bolt at a time was removed and replaced so that workers could install a wire wrap and seal the leak. The replacement bolts were longer and had injection collars. Workers would do the wire wrap and inject the bolts with a sealant to stop the leak. At 1:00 a.m. on December 23, 2021, an employee was working for the contracting firm that would remove and replace the bolts, while the other contractor assisted. As the employee was waiting for the other contractor, an explosion occurred during the repair. The employee suffered second-degree burns. In addition, he suffered a fractured femur when he was struck by a flying object from the explosion. He was hospitalized. Another worker there was not hospitalized. The employee's supervisors knew that the flange had auto ignited the day before they were called to come and fix the leak. The supervisors did not, though, ensure that employees had upgraded their personal protective equipment (PPE) to reduce the risk of serious injuries should a flash fire reoccur. They did not evaluate the hazards and select and require the use of appropriate PPE using their knowledge of the operating conditions, nor did they use refinery owner's safe work practice requirement of using upgraded PPE when work activity is going to be done in areas with potential flash fire.