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?