Sodium azide (NaN3) is a rapidly acting, potentially deadly chemical that exists as an odorless white solid. When it is mixed with water or an acid, sodium azide changes rapidly to a toxic gas with a pungent (sharp) odor. It also changes into a toxic gas when it comes in contact with solid metals (for example, when it is poured into a drain pipe containing lead or copper). The odor of the gas may not be sharp enough, however, to give people sufficient warning of the danger.