| Name: | Oxygen |
| Symbol: | O |
| Atomic Numer: | 8 |
Oxygen is a gaseous element common in the atmosphere of Class M planets, although at relatively low levels (about 20% on Earth, for example).
Oxygen is vital for the survival of most carbon-based lifeforms. Some lifeforms, however, have adapted to go without oxygen for extended periods of time, such as Fantome from The Void, who had a very large lung capacity. (VOY: The Void) Other species, such as Vulcans, have learned to control their vital functions, and can greatly reduce their intake of oxygen through meditation.
One species, the Benzites, can not breathe the oxygen-nitrogen atmosphere deemed normal by most Federation species. (TNG: Coming of Age)
Oxygen is also a critical component of life support functions aboard all space-going craft.