Abstract: At 8:30 a.m. on June 5, 2017, an employee was disassembling a pneumatic cylinder to replace its piston rings. He successfully completed the swap and reassembled the cylinder, which was resting on a work bench in the maintenance shop. After reassembling the cylinder, the employee discovered the piston required further adjustment. When the employee failed to manually pull the piston from the cylinder, he attached a compressed air hose (factory air set at 85 psi) and began to induce air (via fixed ball valve) into the cylinder. After feathering an unknown amount of compressed air into the unbolted unit, the employee closed the ball valve and walked to the other side of the unit. The piston and cylinder separated under the stored pressure and struck the employee in his abdomen. The employee sustained a laceration to his abdominal artery, which he was hospitalized and received treatment.