On 4/26/16, at approximately 5:15 AM, an employee was using a pneumatic chipping gun to break up hardened mortar inside the mortar mixer. When he connected his chipping gun's quick-connect hose to the airline, he accidentally hooked it to an oxygen line, which was not properly labeled. While he was operating the chipping gun with oxygen instead of compressed air, a fire broke out inside the tool and enveloped his right arm, face, and neck. He suffered second and third degree burns to his arm, and first and second degree burns to his face and neck, requiring hospitalization.