Hydraulic systems are under constant pressure, with pounds-per-square inch (PSI) forces in the thousands. The high pressures are necessary to perform the tough jobs required by hydraulic equipment, but they can also leave humans and property vulnerable if not properly handled.
An obvious danger posed by hydraulic hoses and fittings is the sudden release of hydraulic fluid at high pressure. Even a pinhole leak at high pressures can have terrible consequences for those who may be in the path of fluids. High pressure injection injuries can result in amputation of extremities, for example.
Another potentially deadly hazard of working with hydraulic hoses and fittings is the explosive release of energy occurring during a release. A burst hose can thrash about violently and strike others or destroy property.