|This article is about High Capacity O₂ Tank in Subnautica. For the related article on the Below Zero Wiki, see High_Capacity_O₂_Tank.|
|This article is about the High Capacity O2 Tank. If this is not what you are looking for, see Oxygen Tank (Disambiguation).|
The High Capacity O₂ Tank is an upgrade to the Standard O₂ Tank that is crafted at the Fabricator, being the only upgrade not requiring a Modification Station. It can only be crafted after the player has acquired a Standard O₂ Tank. While equipped, it boosts the player's maximum Oxygen supply by 90 units for a total of 135 units.
The player must equip the High Capacity O2 Tank in the tank slot of the Paperdoll UI in order to benefit from it. While not equipped, it takes six slots (2×3) in the inventory.
Note that when an O2 tank of any kind is built, it defaults to being empty: it must be equipped in an atmosphere in order to fill it. This is important if the player intends to carry multiple tanks for deep diving without a vehicle.