Samus Aran's Power Suit uses Oxygen Supply Equipment to help her breathe in certain atmospheres, such as the extreme heat of Norfair on Zebes, Magmoor Caverns on Tallon IV and Sector 3 on the BSL. It can be upgraded to function more efficiently in other environments that are more dangerous, such as Dark Aether. The predecessor to this device was the skin pouch employed by Chozo warriors.
It does not have much significance to the series, but plays a role in the Captain N: The Game Master comic When Friends Fall Out, in which it is referred to as the air supply valve. Princess Lana uses it against Samus during their fight, when Lana believes Samus is culpable in the forced disappearance of her father. Lana stuns Samus by finding her air supply valve and using it to flood the Power Suit with pure oxygen. It was later named in the manual for Metroid II: Return of Samus.