Liquid oxygen supply systems for breathing oxygen for the crew and/or passengers of transport aircraft require design and installation considerations@ which are detailed herein. AIR 825@ Oxygen Equipment for Aircraft@ contains general information on determination of breathing oxygen requirements and equipment for the crew and passengers of transport category aircraft. This document covers the more specific requirements for either a 70 or 300 psig liquid oxygen system. The standard 70 psig nominal pressure is recommended for use except in cases of excessive pressure drop@ flow requirements@ and some continuous flow regulators which may require the 300 psig nominal pressure system. AS 861@ Minimum General Standards for Oxygen Systems and AIR 822@ Oxygen Systems for General Aviation Aircraft@ also contain general applicable information. Note: When Military Specification components are referenced in this document@ it is intended that this be interpreted as a guide and that components functionally equivalent to these units may be used.