Section R. 408.11253 - Hoses and connectionsRule 1253.
(1) Only approved hose and connections shall be used. A hose connection shall be fastened to withstand twice the working pressure without leaking, but not less than 300 psig (2070 kPa). Oil-free air or an oil-free inert gas shall be used for the test.(2) Parallel lengths of hose taped together shall have not more than 4 inches out of each 12 covered by tape.(3) Parallel hoses shall be color coded as follows:(c) Black--inert gas or air.(4) A hose shall be repaired or replaced when it shows burns, leaks, worn places or other defects which could affect the safety of employees.Mich. Admin. Code R. 408.11253