As oxygen bars begin to pop up across France, health authorities are beginning to question the merits or otherwise of sniffing O2.
Supposed to improve health and well-being, oxygen bars date back to the late 1990s, spreading from Canada to California and to Britain and Japan, in nightclubs, health clubs, airports or even trade fairs.
But Paris' first oxygen bar opened only last week.
Flagged as "a revolutionary anti-fatigue, anti-stress and anti-depression concept", the city's maiden O2 bar is housed in an up-market beauty institute owned by no less than the wife of top French publicist and political "kingmaker" Jacques Seguela.
Seguela has been very much in the news recently for bringing together President Nicolas Sarkozy and his new wife Carla Bruni around a dinner table, a coup that comes almost three decades after helping propel leftwing leader Francois Mitterrand to the country's highest public office.
So the opening of his oxygen taps a stone throw's from the Champs-Elysees attracted a bevy of French celebs and political high-fliers from across the spectrum.
"This is the first time you can legally shoot up!" said Seguela, showing his VIP guests the rows of oxygen bottles lined up in different parts of the salon.
But the politicians -- including a current cabinet member and two ex-ministers -- were cautious.
"It has more of a psychological rather than a technical effect," said former leftwing culture minister Jack Lang after inhaling a dose of oxygen flavoured with essential oils bubbling in a jar.
Oxygen bars offer sniffers an increased percentage (up to 95 percent) of oxygen compared to the normal atmospheric content of 21 percent -- lower in the case of severe pollution.
Guests need to inhale for at least 10 minutes "to feel the effect", said Jean-Guillaume Laurent, who works for the Colian company that sells O2 equipment in France.
"Not bad," said Labour Minister Xavier Bertrand after a sniff.
"It looks great," said philosopher and former rightwing education minister Luc Ferry.
"It does clear your nose," said a more practical young woman nearby.
O2 bars have already opened in other parts of France, in Saint-Tropez on the French Riviera, at the Deauville casino, and in Strasbourg on the border with Germany. And as in other countries, oxygen-sniffing is increasingly popular at promotional events.
But with oxygen concentrated at 99.5 percent considered to be medicine (for breathing problems notably), authorities are scratching their heads over whether or not to regulate trendy O2 bars.
The French Drugs Agency (Afssaps) told AFP that it had "begun reflecting about oxygen bars."
"We are asking ourselves questions. Is this or is this not a health product?" said Marie-Laurence Gourlay, who is in charge of the proper use of health products for Afssaps.
"We know that at some levels of concentration (more than 99.5 percent) and over long periods (more than six hours), oxygen can be harmful for the lungs and the central nervous system," she said.
Most oxygen bars suggest inhaling between five and 20 minutes.
Essential oils, Gourlay added, could also be a health risk depending on the type of oil, its concentration and the way it is administered.
And with some of the oil-and-oxygen concoctions claiming to help fight headaches and head-colds, the agency in the future will be keeping a close eye on O2 bars, she said.