Abstract: On or about June 21, 2013, Employees #1, #2, and #3, electrical power installers, plus Employee #4, who was the work crew superintendent, plus Coworkers #1, #2, and #3, all of Utec Constructors Corporation, were installing insulation to electrical power transmission lines. The lines were in eight conduits along a road. Nitrogen was being used for the insulation. An 18-wheel trailer contained 10 tubes of nitrogen, with a total volume of approximately 100,000 cubic feet. Four of the workers were standing on or around the back of the trailer, and the superintendent was standing along the left side of the trailer. Two workers were in a manhole and operating valves where a hose attached to the manifold on the back of the trailer. The superintendent instructed the crew to open the valves. He then noticed that the valve on the manifold in line behind the nitrogen flow meter was leaking. He said to close the valve, meaning to close the valve on the nitrogen tube. Instead, the valve on the conduit in the manhole was closed. Closing this valve caused a buildup of pressure. As a result of this pressure, the glass portion of the flow meter failed and shattered. When the glass shattered, Employees #1, #2, #3, and #4 were struck by flying glass. They were transported to the Medical University of South Carolina (MUSC Health). Employees #1, #2, and #4 were treated for cuts and bruises to the face, and Employee #3 was treated for cuts to the left wrist. Employee #1 was admitted for an overnight stay. Employees #2, #3, and #4 were released without hospitalization. At the time of this report, all the injured employees were continuing to recover. The subsequent investigation determined that the nitrogen flow meter was manufactured by SK Micrometer. The investigator was unable to verify the model number, which had been on the glass that shattered. All employees were wearing appropriate PPE, including hard hats, safety glasses, and work boots. The two employees in the manhole were also wearing harnesses and lanyards. There had been an oxygen meter, blower fan, and hoisting equipment above one of the manhole openings.