This webpage is maintained by the Centers for Disease Control and Prevention (CDC). The webpage provides information and resources on Sodium Azide. "Sodium azide 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 (hydrazoic acid) 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."
Centers for Disease Control and Prevention: http://www.cdc.gov/