<prompt> Safety pin index for oxygen cylinder is?2, 53,51,51,4  <response>: Ans. is a i.e., 2, 5 Gas Pin index Oxygen 2,5 Nitrous oxide 3,5 Cyclopropane 3, 6 Air 1, 5 Nitrogen 1, 4 Entonox 50 02 50N,0 Single central 7 Carbon dioxide 7.5 2, 6 Carbon dioxide 7.5 1, 6 