Abstract: A portable breathable gas delivery device including a pressure vessel for storing the breathable gas under pressure and a valve coupled to the pressure vessel through which the breathable gas can be selectively released. The pressure vessel is enclosed in a housing having a first portion that at least partially encloses the pressure vessel and a second portion that partially encloses a chamber coupled to the pressure vessel via the valve into which the breathable gas can be released for breathing by a user. The second portion together with a user's facial structure forms a substantially closed enclosure. The chamber has an opening shaped and formed to interface with the user's facial structure.