Oxygen bar.

Ever wonder what all those toxins in the air might be doing to your lungs? The [O.sub.2], Spa Bar in Toronto, Canada, is giving customers a clean alternative - 20 minutes of 99 percent pure oxygen for $16. Just tuck the plastic plugs in your nostrils, lean back and inhale.

You are what you breathe, claim Lissa Charron and Shamila Hunter, who opened North America's first oxygen bar last spring. Their [O.sub.2] treatment, they insist, will purify your body.

Doctors call it a sham. Pure oxygen, they say, does nothing to cleanse your body. And it can be harmful - particularly for people with severe lung diseases like emphysema.

People breathe for two reasons. First, our bodies "tell" us to take in oxygen. Second, we need to rid our bodies of carbon dioxide, a toxic gas that cells discard.

But people with severe lung disease often lose the ability to respond to the carbon dioxide "signal." Their bodies only tell them to breathe when they need oxygen. Give them pure oxygen and their bodies think they don't need to breathe. So they don't. Their cells fill up with toxic carbon dioxide, which can lead to death.

Even if you don't have a severe lung problem, breathing pure [O.sub.2] for an extended period of time can be dangerous. After 24 hours, it can cause fluid to build up in your lungs, leading to lung collapse. But a typical dose - say, 20 minutes at the [O.sub.2] bar - probably won't cause any harm.

And the trend is on, with oxygen bars slated to open soon in New York and Los Angeles. You must be at least 16 to get in. Would you want to?