Breathe deeply, wherever you are, and what do you smell? Chances are you're surrounded by a pleasing scent, whether it's floral, or woodsy, or fruity (Thai Dragon Fruit, anyone?). Or perhaps it's the scent of fresh linen or ocean breeze, or any one of dozens of euphemistically named "air fresheners" marketed by dozens of companies in an industry that brings in about $7 billion a year worldwide. Yes, that's billion.