The O2 Mask (not to be represented as O2 Mask) is a helmet Gadget from the original Ratchet & Clank that allows Ratchet to breathe in any environment, primarily underwater, in the vacuum of space, and in toxic atmospheres. It is not bought, rather it is earned in Jowai Resort on Pokitaru. It is very similar to the rebreather on Ratchet's Commando Helmet and the Oxygen Mask in the Future series.
The quest for the O2 Mask takes up a significant part of the middle of Ratchet & Clank 1. Ratchet and Clank discover an Infobot on Orxon advertising the O2 Mask being given to you if you visit Jowai Resort. However the Blarg were dumping toxic sludge into the ocean, so the Resort Owner would only give Ratchet the mask if he shot down the dumping ships. Things got complicated when the garage with the Jet Fighter in it was locked, and Ratchet had to purchase the Thruster Pack in order to open it (Ratchet would also need the Pilot's Helmet from Gaspar in order to actually fly the fighter). After shooting down the dumping ships, Ratchet would at last acquire the O2 Mask.
The O2 Mask equips automatically whenever it is needed, but being a Gadget it can also be equipped manually as well. With it, Ratchet is able to go into many areas he otherwise couldn't, the most immediate of which is underwater. While he cound spend time underwater, he was limited by how long he could hold his breath, but the O2 Mask allows him to breathe underwater indefinately. Combined with the Hydro-Pack, this makes Ratchet's underwater exploration potential much greater than before.
In addition to underwater breathing, the O2 Mask also lets Ratchet explore in the vacuum of space (as seen in the Drek's Fleet level) and in toxic atmospheres such as Orxon's. In fact progression is halted if Ratchet does not acquire the O2 Mask to help him breathe on Orxon; until then Clank can only explore there. Because there is no air in the vacuum of space, it can be taken that the O2 Mask does not siphon in only oxygen (as happens with a fish's gills), it actually has its own oxygen supply to provide Ratchet.
- The design and function of the O2 Mask is very similar to the real word Gas Mask.
- While the O2 Mask allows Ratchet to at least breathe in the vacuum of space, it is never explained how he is able to survive in space. This curiosity is also shared by Captain Qwark, as seen in Up Your Arsenal, A Crack in Time and Secret Agent Clank. In fact it was even brought up by Barney, Qwark's biographer, in Secret Agent Clank, but Qwark dodged the question, keeping the mystery ongoing.
- In most cutscenes where Ratchet is wearing the O2 Mask, Ratchet's mouth isn't animated due to being blocked by the mask. However, in one scene on Orxon, his mouth for some reason is. This may be because the location the scene took place in was meant to occur inside a pocket of air.
- The scenes depicting Ratchet drinking the Nanotech upgrades on Orxon do occur in a pocket of air, likely because Ratchet would had to have taken off the helmet in order to drink the upgrades, and the O2 Mask covers his entire face.