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This article is about Oxygen in Subnautica. To see this subject's article on the Subnautica: Below Zero Wiki, click here.
O2

Oxygen (O2) is a gas that is needed by the player to survive. When diving, the player uses a reserve of oxygen that diminishes over time. If the player runs out of oxygen, the player's screen will begin fading to black, and they will have about 4 seconds to get to air source before the screen completely fades out and they die. 

The player's oxygen reserve automatically replenishes whenever they:

  • come up to the surface
  • enter a powered vehicle or Seabase
  • approach the end of a functioning Pipe
  • come into contact with bubbles released from Brain Coral
  • eat a raw Bladderfish
  • simply swap their O2 tank to a not yet depleted one.

Oxygen is produced within a Seabase, Seamoth, Prawn Suit, and Cyclops naturally, as long as they have energy. If they run out of power, no oxygen will be produced. oxygen is always present in Lifepod 5. oxygen production itself costs no energy, only powered state is required.

The HUD indicator for the player's oxygen supply is located on the bottom left of the screen. The player has a base reserve of 45 units of oxygen, which can be increased by 30 units by equipping a Standard O2 Tank or by up to 225 units with upgraded tanks.

The PDA will alert the player if they have less than 10 oxygen remaining. The PDA will also alert the player when they have 30 oxygen remaining, if they are diving far from the surface and don't have a tank equipped.[1] The PDA will not play these alerts in Hardcore Mode.

The depth to which the player dives affects the rate of oxygen consumption. When diving less than 100m, the player will consume one unit per second; when diving between 100m and 200m, three units are consumed per second; when diving deeper than 200m, five units are consumed per second. This can be counteracted completely by equipping a Rebreather.

If the interior of a Cyclops catches fire, it will produce smoke, which will, over time, cause the player to run out of oxygen and suffocate.

Trivia

  • The player can use the console command oxygen to have unlimited oxygen.
  • If the player is depleted of oxygen and gets to the surface when the screen is fading, different breathing responses will occur coming from the player.
  • One of the unused game sound files states that the atmosphere also contains nitrogen, likely making it very Earth like. It doesn't mention percentage contents, however.

References

  1. The alerts play when there are 10 and 30 units left. The first one simply says "Oxygen", and the second one says "30 seconds of Oxygen remaining." However, depending on the current depth, the player can deplete three or five units per second, so when the alert says "30 seconds of Oxygen remaining," there could be actually less than 10 seconds.