Diluter demand oxygen system

A popular type of breathing oxygen system in which oxygen is metered to the mask where it is diluted with cabin air by an airflow-metering aneroid assembly which regulates the amount of air allowed to dilute the oxygen on the basis of cabin altitude. As the aircraft goes to higher altitude, the amount of cabin air metered into the oxygen is automatically decreased until at about 34,000 feet, the cabin air is entirely shut off and the regulator sends 100% oxygen to the mask. The oxygen and air flow to the mask only when the wearer inhales, but the regulators have an emergency position which allows the pilot to manually bypass the demand function and sends a continuous flow of 100% oxygen to the mask.