Oxygen is a chemical element with the symbol O and the atomic number 8
In the aerospace context, oxygen refers to the gas that is used by the crew and passengers of aircraft and spacecraft to breathe.
Oxygen is necessary for human life and is required in order to sustain the physiological processes that keep the body functioning. In aircraft and spacecraft, oxygen is typically stored in tanks and is supplied to the crew and passengers through a system of tubes and regulators. Some aircraft and spacecraft have systems that generate oxygen from the surrounding air, while others carry tanks of pure oxygen for use in emergency situations. Oxygen is also used in some spacecraft and aircraft for other purposes, such as to start fires for propulsion or to cool certain parts of the vehicle.