Longman Dictionary of Contemporary English
oxygen bar
noun
EXAMPLES FROM CORPUS
▪ The Takashimaya department store in Tokyo has an oxygen bar.
Wiktionary
oxygen bar
n. A nightclub or similar venue in which patrons pay to inhale doses of gas containing concentrations of oxygen higher than in air.
Wikipedia
Oxygen bar
An oxygen bar is an establishment, or part of one, that sells oxygen for recreational use. Individual flavored scents may be added to enhance the experience. The flavors in an oxygen bar come from bubbling oxygen through bottles containing aromatic solutions before it reaches the nostrils: most bars use food-grade particles to produce the scent, but some bars use aroma oils.