This webpage is maintained by the Centers for Disease Control and Prevention (CDC). The webpage provides information and resources on Cyanide. "[...] Cyanide is a rapidly acting, potentially deadly chemical that can exist in various forms. [...] Cyanide can be a colorless gas, such as hydrogen cyanide (HCN) or cyanogen chloride (CNCl), or a crystal form such as sodium cyanide (NaCN) or potassium cyanide (KCN). [...] Cyanide sometimes is described as having a "bitter almond" smell, but it does not always give off an odor, and not everyone can detect this odor. [...] Cyanide is also known by the military designations AC (for hydrogen cyanide) and CK (for cyanogen chloride)."
Centers for Disease Control and Prevention: http://www.cdc.gov/