Oxygen is the second largest component of the atmosphere, comprising 20.8% by volume. Liquid oxygen is pale blue and extremely cold. Although nonflammable, oxygen is a strong oxidizer.Oxygen is necessary to support life.
Oxygen will react with nearly all organic materials and metals usually forming an oxide. Materials that burn in air will burn more vigorously in oxygen. Equipment used in oxygen service must meet stringent cleaning requirements and systems must be constructed of materials that have high ignition temperatures and that are non-reactive with oxygen under the service conditions.