Now, customers pay through the nose to breathe scented, purified, highly oxygenated air in nightclubs and day spas in cities big and small, from Sacramento, Calif., to Ann Arbor, Mich., from Las Vegas to Asheville, N.C. The average price per minute of air: about $1.
But critics -- and there are many -- wish oxygen bars would go the way of the Y2K bug and 21-year-old dot-com millionaires.
They say there are no medical studies that show breathing oxygen in the manner it's dispensed at oxygen bars has any health benefits whatsoever. And too much oxygen, especially for people with certain medical conditions, can be harmful.
"Based on our understanding of the science, it's very hard to believe that the oxygen used in oxygen bars can be of any benefit," says Dr. Norman Edelman, consultant for scientific affairs with the American Lung Association and vice president for health sciences at Stony Brook University in New York.
"And we also want to caution people that breathing pure oxygen for extended periods of time can cause respiratory problems," Edelman adds.
But oxygen bar proprietors such as Lisa Hinchey shrug off the criticism.
She runs the 2202 Oxygen Bar and Organic Cafe in San Francisco. "Doctors don't want you to do it because it takes money away from them. It detoxifies your blood cells, it gives you more stamina, it gives you pure, fresh energy, not like caffeine energy," she says.
Hinchey says she breathes the oxygen at her bar for 40 minutes, three times a week.
"I feel really good and relaxed," she says. "I sleep more soundly. I wake up more happy, it lifts up my spirit, it rejuvenates me. I'm more at peace with oxygen in my bloodstream."
She says her clients include marathon runners, students preparing for their SATs, even older couples before they have sex.
Oxygen bars first appeared in Japan, Mexico and South America, where concerns about air pollution lead to an interest in breathing purified air, says Dr. Ron Balkissoon, a pulmonologist at the National Jewish Medical and Research Center in Denver.
By the late 90s, oxygen bars began appearing in major U.S. cities. Actor Woody Harrelson, best known for his role as the dim-witted bartender on the sitcom Cheers, opened one of the first on the Sunset Strip in Los Angeles.
Then the U.S. Food and Drug Administration got wind of what was going on. Under the Federal Food, Drug and Cosmetic Act, any type of oxygen that's "used for breathing and administered by another person is a prescription drug," according to a recent article in the FDA Consumer magazine.
That means oxygen bars violate FDA regulations. Still, the agency leaves enforcement up to each state licensing board. "Many states choose to allow oxygen bars; others discourage the businesses by requiring strict compliance with the law," according to the article.
No matter if those rules are enforced or not, there's one thing oxygen bar owners can't do in any state -- make claims that oxygen can treat or cure illnesses.
To stay out of trouble, most oxygen bar owners avoid those claims, Balkissoon says. Instead, they say oxygen helps you relax, reduces stress, increases energy or alertness, and promotes general feelings of well-being.
But there's no medical evidence that says any of this is true, Balkissoon says.
Besides, all the oxygen that healthy people need is right under their nose.
Air normally contains about 21 percent oxygen. At an oxygen bar, customers typically breathe the oxygen through a cannula, a two-pronged tube that fits loosely in the nostrils.
While the air coming out of the cannula might be nearly 100 percent oxygen, the person inhaling it will probably breathe from 50 percent to 75 percent oxygen because they're still inhaling some room air, Balkissoon says.
If that sounds super healthy, think again.
In a healthy person, the hemoglobin in blood that transports oxygen is already 98 to 99 percent saturated with oxygen. Upping it another percentage point by breathing highly oxygenated air will have "absolutely no physiological effect," says Balkissoon. "Any extra oxygen gets exhaled right back out. Your body can't hold onto it."
And while it probably would not happen in an oxygen bar, too much oxygen can be toxic. Excess oxygen can increase the production of free radicals, which can damage tissues and kill cells, he says. Over time, this can hinder brain, heart, lung, muscle and memory function.
Complications of excessive oxygen can also include pulmonary edema, or fluid on the lungs.
There are other concerns. Some oxygen bars used scented air in flavors ranging from eucalyptus to raspberry to mint.
If the scent is oil-based, it's possible that tiny droplets of oil can be inhaled into the lungs, leading to a type of pneumonia called lipoid pneumonia, Edelman says.
People with emphysema or other chronic pulmonary obstructive disease should definitely stay away. For people already oxygen-compromised, breathing in too much oxygen can actually suppress their drive to breathe, Balkissoon says.
This can cause a buildup of carbon dioxide in their lungs, he says.
Finally, if you see an oxygen bar in a nightclub where people smoke, stay away, Balkissoon says. Oxygen feeds fires. "If you have any kind of a flame, and it comes into contact with pure oxygen, the flame will get bigger and bigger," he says. "They could blow up the bar."