The information provided in AIR825/6 applies to On Board Oxygen Generating Systems (OBOGS) - Molecular Sieve@ that utilize the ability of molecular sieve materials by using Pressure Swing Adsorption Process (PSA) to separate and concentrate oxygen in the product gas from the surrounding air@ respectively air provided by any compressor or by the aircraft engine (so called: Bleed Air)@ and to provide this oxygen enriched air or product gas as supplemental oxygen for breathing gas supply of crew and passengers onboard aircraft. The distribution system and the provided oxygen concentration have to fulfill the respective airworthiness regulations. Equipment using this technology is to provide supplemental oxygen for breathing gas supply of crew and passengers onboard aircraft@ the suitable breathing gas oxygen partial pressure or oxygen concentration requirements are specified in AIR825/2 and the oxygen purity requirements in AS8010. NOTE: OBOGS has never been certified for commercial aircraft. The 14 CFR/CS 25 as well as 14 CFR 121/Commission Regulation (EU) N??65/2012@ amended need to be reviewed and if necessary amended prior to introduction of OBOGS. Alternatively@ such certification will likely incorporate various special conditions that address differences in performance between OBOGS and conventional systems. These systems are intended for: a. The on-line breathing gas supply to directly account for the normal oxygen usage of crew and passengers in terms of: 1. Supplemental oxygen for part or all of an emergency descent 2. Supplemental oxygen for first aid 3. Therapeutic oxygen b. The replenishment of the aircraft gaseous oxygen system storage cylinders to account for the normal oxygen usage of crew and passengers and system leakage c. A combination of the above. The possible applicability and benefit of incorporation of OBOGS-Molecular Sieve into non-military aircraft is being considered by the representatives of Civil Aviation. The intended aim of AIR825/6 is to provide a fundamental description of the function of existing OBOGS-Molecular-Sieve systems with a related reference to the type of oxygen standards which would merit a review.