Abstract: An instrument technician for an electric utility was assigned to test an air outlet bleed-off line at the base of a generator tower. The tower was under partial reconstruction, and the employee was testing the system before the utility took over this part of the project. The valve for the line had been improperly installed by a subcontractor's employee, who had assembled a compression fitting with the flared end of the tubing backwards. After pressurizing the system to 830 pascals with a temporary bank of compressed air tanks, the technician placed his hand on the bleed-off valve handle. The valve and about 1 meter of 6-millimeter diameter tubing blew off. The valve and tubing struck the employee in the chest with enough force to knock him down. He received a fractured pelvis in the fall. He was hospitalized for his injuries.