What is the special requirement for the type of oxygen used in an aircraft system?

Only aviator's breathing oxygen should be used in aircraft systems because it is specifically formulated to meet the needs of high-altitude flight and will not contain harmful impurities that could be present in other types of oxygen. Aviator's breathing oxygen is manufactured to comply with rigorous aviation standards, ensuring it is dry, free of contaminants, and safe for the respiratory systems of pilots and passengers.

Using industrial-grade oxygen could introduce contaminants that are harmful in the pressurized environments of an aircraft. Medical oxygen, while typically pure, does not meet the specific standards required for aviation use, potentially leading to safety issues. Cryogenic oxygen, although also pure, is not practical for aviation systems due to the complexities and risks associated with handling such low temperatures. Therefore, the use of aviator's breathing oxygen is essential for maintaining safety and health during flight operations.