This report has been prepared as a revision of the previous Aerospace Information Report No. 825 dated February 25@ 1965@ in order to bring that report up to date by including the latest information available on the design and use of aircraft oxygen systems. Accordingly@ it supersedes AIR 825. The publication issue is broken down into six (6) sections as follows: Section I Oxygen -- Basic Physiology Section II Gaseous Oxygen and Oxygen Equipment@ Introductory Section III Continuous Flow Oxygen Systems Section IV Demand and Pressure Demand Oxygen Systems Section V Liquid Oxygen Systems Section VI Charts@ Tables and Systems Schematics