Zyklon B was the trade name of a cyanide-based pesticide infamous for its use by Nazi Germany to kill human beings in gas chambers of extermination camps during the Holocaust. Zyklon B consisted of hydrogen cyanide (prussic acid), a stabilizer, a warning odorant ethyl bromoacetate, and one of several adsorbents. The Zyklon B used for mass killings of humans regularly omitted the warning odorant.