Mothers around the world know that fresh air is good for you--or as a scientist could tell you, bad for bacteria. Now a UK company has developed a product that produces hydroxyl radicals by reacting terpenes (a class of hydrocarbons produced by plants and contained in many essential oils) with atmospheric ozone. The germkilling radicals, consisting of a neutral but highly reactive OH molecule with an unpaired electron, prevent bacteria from absorbing nutrients properly, but are harmless to humans. Hospitals, lately worried about the threat of 'superbug' epidemics--infections of antibiotic-resistant bacteria, could reduce a heavily contaminated room to below infectious levels in minutes. And doesn't that smell sweet?