Very small cracks or pin-holes can expel hydraulic fluid at extreme velocities, much like a high pressure water sprayer or pneumatic paint gun. These high velocity fluid jets can not only penetrate the skin and inject hydraulic fluid into your blood stream, they can cut through fabrics (gloves, shirts, pants) and do damage just about anywhere. If you get sprayed in the eye it can do permanent damage to your cornea, or worse cause total blindless (yet another reason for safety glasses!).
Hydraulic fluid can be hot, which can lead to unnecessary burns; it can be flammable, which can lead to fire hazards; and it can be very slippery, which can lead to slip and fall accidents.
Safe-T-Bleed company has introduced a pressure bleeding manifold valve the facilitates the safe shut-down of hydraulic lines before they are disconnected for service. The Hydraulic Energy Control Module (HECM) can be used in-line with any system line up to 5000 psi.
The product web site has several pages of good-to-know info about OSHA compliance with hydraulic systems - visit and get your LOTO knowledge up-to-date.