An employee was inflating a tubeless lawn mower tire utilizing a lock-on air chuck to seal off leaks and seat the bead. To verify the bead was successfully seated, the employee placed water on the seam of each side of the tire. He noticed a small leak in the seam on the side opposite the valve stem and the employee added more air to seal off the leak. The tire was laying flat on the ground with the valve stem facing up. As he removed the air chuck from the tire, the seam failed and blew the tire and rim upward, striking the employee in the forehead. He was hospitalized for a forehead laceration.