The oxygen in oxygen bars comes from completely self-contained machines called oxygen concentrators (non-medical). These non-medical concentrators use a technology called Pressure Swing Adsorption, a NASA created technology that filters out Nitrogen, Argon and other trace gasses from the ambient air. This technology then puts the separated oxygen molecule to 92% purity to the recipient and the Nitrogen and other gasses get released back into the atmosphere. Once the oxygen bar equipment is purchased you never have to buy oxygen ever again!
Where do you get the oxygen?