Abstract: Employee #1, who worked for Advanced Industrial Services, was dispatched to a customer's premises to repair a malfunctioning hydraulic system. At about 2:00 p.m., to replace a defective High Pressure Sensing Switch, Employee #1 began unscrewing it. The hydraulic system had not been bled completely to release the internal pressure, nor had any other method been utilized to prevent the sudden release of pressure or spraying of liquid prior to removing the defective switch. While Employee #1 was removing the High switch, Employee #2, from the facility where the repair was taking place, was bleeding the hydraulic lines. The Pressure Sensing Switch suddenly came off and struck Employee #1 on the head. Employee #1 was hospitalized for cuts and lacerations.