Just to be perfectly clear on this tricky subject.
Grade R-RM fuel gas hoses are for acetylene only.
http://www.parker.com/ead/cm2.asp?cmid=3782
Grade T fuel gas hoses can be used with Acetylene, Mapp, Propylene, Hydrogen, Propane and natural gas.
http://www.parker.com/ead/cm2.asp?cmid=3757
Check and see what you currently have.