The injured person was changing out fittings from a blue bypass valve (pressure approximately 5000 psi). He was attempting to bleed off the pressure on the line between the Moonpool and the High Pressure Unit by loosening a 3/8 inch compression fitting on a stainless steel high pressure tubing. The injured person was holding the tubing in place covered with a rag when depressurizing the line. As the tubing nut was being loosened, high-pressure BOP fluid was released off the line through the ferrule. The high-pressure BOP fluid along with particles of the rag were injected into the injured person’s hand.