The O2 Mask is a gadget in Ratchet & Clank, and an item in Tools of Destruction, Quest for Booty, A Crack in Time, and Ratchet & Clank (2016 game). It allows Ratchet to breathe in any environment, including underwater, toxic atmospheres, and in space, by synthesizing and recycling a supply of oxygen. In the original Ratchet & Clank, the O2 Mask is initially acquired by Ratchet at Jowai Resort on Pokitaru, granted by Resort Owner by completing "Destroy the blarg ships". In the re-imagined Ratchet & Clank, the O2 Mask is instead an optional gadget acquired by exploring the pumping stations.
In other releases, the O2 Mask is available from the start. The Megacorp Helmet in Going Commando and Up Your Arsenal provides the same functionality as the O2 Mask.
In the original Ratchet & Clank, the gadget is not immediately available, and acquiring it makes a significant difference to the gameplay. It allows Ratchet to swim indefinitely and breathe in space, reaching new areas required to complete several missions. It also allows Ratchet to access some areas previously only available to Clank, such as Orxon and the outside of the Blarg Tactical Research Station. It also allows Ratchet to avoid damage from Extermibots and Extermitanks firing toxic gas on Rilgar.
Behind the scenes
A redesigned, smaller O2 Mask fitting the face and mouth appears in the 2016 reboot. It is acquired in the same place on Pokitaru, though it is found in the pumping stations as an optional item rather than through the main path. The weapon also does not allow Ratchet to visit Clank's area in the Blarg Tactical Research Station, as this is too small for him to fit through.