Abstract: At 1:25 p.m. on August 14, 2020, an employee was tasked to repair a leak on an aluminum tanker truck that previously hauled gasoline and diesel fuel. The tanker had a 700 gallon gasoline tank and a 3,000 gallon diesel tank. The leak occurred in the dead air space cavity between the two tanks. The truck was pre-cleaned and had just been delivered to the shop from a third party steaming service. The employee opened up the manhole covers and determined that the dead air space had a strong smell of fuel vapors. The employer directed the employee to resteam the tanks and dead air space with the shop's steaming system. The employee performed steaming in the tanks and brought the tanker back into the building. The employee pressurized the dead air space with compressed air and soaped down the front head of the rear tank to identify the leak location. The employee removed a support pad with a grinding wheel to access a cracked weld. The employee prepared the cracked area with the grinder and began to perform welding over the cracked area when an explosion occurred within the dead air space cavity. The force from the explosion caused the front head of the rear tank to blow out toward the employee. The employee was propelled to the back of the tank and was rendered unconscious. A coworker called 911 and the fire department had to cut a hole in the side of the tank to extract the employee. The employee was hospitalized for over two months to treat traumatic brain injuries, multiple broken ribs, a broken right clavicle, lacerations and bruising.