Rebreather

A Rebreather is a device used to provide a supply of oxygen in anoxic or otherwise toxic atmospheric environments. Consisting of a mask or helmet, rebreathers contain their own air supply and are designed to preserve the user in even the most toxic atmospheres. A person wearing a rebreather is immune to the effects of gases and can even survive underwater. However, rebreathers typically have oxygen canisters that last for about one solar hour and then must be replaced.