If you're not savvy enough to trick a doctor into a prescription for medical marijuana, then get your high the legal way -- at 2202 Oxygen Bar. Any "drug" is expensive, and the O2 served up at this hip Mission bar is no different. At $10 a pop for a 10-minute session ($15 for 20 minutes and $25 for 40 minutes), the uplifting elixir is more expensive than a fancy cocktail you can nurse for half an hour. But it's infinitely healthier. According to oxygen addicts (and really, who isn't?), increased oxygen levels treat a variety of symptoms from hangovers and headaches to fatigue and malaise. Your basic oxygen can also be enhanced with aromatherapy blends like Aphrodisia, a tempting concoction of ylang-ylang, sage, bergamot, and blue cypress that will, according to the menu, "encourage feelings of well being and dissolve emotional coldness." A great change of pace from the typical drunken bar scene, 2202 is hip and trendy -- dimly lit; decorated with an intriguing mix of vivid tribal paintings, sleek leather sofas, retro disco balls, and eerie alien masks -- without the attitude. For a surreal experience, visit the bar on a low-key Friday evening when the DJ spins trippy, spaced-out tunes and peaceful patrons stare blissfully into space with oxygen tubes running out their noses. No alcohol is served, although herbal elixirs and tinctures are available.