Oxygen is a colorless, odorless, and tasteless gas. The relative density of gas (air=1) is 1.105 at 21.1℃ and 101.3kPa, and the density of liquid is 1141kg/m3 at the boiling point. Oxygen is not toxic, but exposure to high concentrations of oxygen can have adverse effects on the lungs and central nervous system. Oxygen can be shipped as a non-liquefied gas at a pressure of 13790kPa or as a cryogenic liquid.

Many oxidation reactions in the chemical industry use pure oxygen rather than air in order to benefit from higher reaction rates, easier product separation, higher yields, or smaller equipment size.