A
breathing gas is a mixture of
gaseous chemical elements and compounds used for
respiration. The essential component for any breathing gas is a
partial pressure of
oxygen of between roughly 0.16 and 1.60 bar at the
ambient pressure. The oxygen is usually the only
metabolically active component unless the gas is an anaesthetic mixture. Some of the oxygen in the breathing gas is consumed by the metabolic processes, and the inert components are unchanged, and serve mainly to dilute the oxygen to an appropriate concentration, and are therefore also known as diluent gases.