[1] Blood agents are fast-acting, potentially lethal poisons that typically manifest at room temperature as volatile colorless gases with a faint odor.
[1] Cyanide compounds occur in small amounts in the natural environment and in cigarette smoke.
[2] Arsine gas, formed when arsenic encounters an acid, is used as a pesticide and in the semiconductor industry; most exposures to it occur accidentally in the workplace.
[2] Hydrogen cyanide has a faint, bitter, almond odor that only about half of all people can smell.
[2] Chemical detection methods, in the form of kits or testing strips, exist for hydrogen cyanide.
In enclosed areas, fire extinguishers spraying sodium carbonate can decontaminate hydrogen cyanide, but the resulting metal salts remain poisonous on contact.
[6] One of the earliest proposed chemical weapons, cacodyl oxide, or Cadet's fuming liquid, also displays properties of a blood agent (as well as those of a malodorant).
It was proposed as a chemical weapon in the British Empire during the Crimean War, along with the significantly more potent blood agent, cacodyl cyanide.
[7] The most significant practical application of blood agents was the use of hydrogen cyanide (Zyklon B) in gas chambers by Nazi Germany to commit the mass murder of Jews and others in the course of the Holocaust.