Abstract: On September 20, 2003, Employee #1, a mechanic, and a coworker were repairing a Gradall material handler, Model Number 534-C9, which was located off-site at a client's place of business. The client had reported that the material handler had an oil leak. As Employee #1 examined the hydraulic hoses of the material handler, he told the coworker to start the equipment. Oil squirted out at an approximate pressure of 3,000 psi and oil was injected into Employee #1's left thumb. His thumb got infected, causing necrosis of the tissue, which required surgery. A detailed accident investigation determined that the employees were not properly trained regarding hazards associated with hydraulic hoses and proper techniques for troubleshooting leaks. The employee was hospitalized.