Humanities › History & Culture Zyklon B, a Poison Used During the Holocaust The cyanide was used in the gas chambers at Auschwitz and elsewhere Share Flipboard Email Print Julian Herbert / Getty Images History & Culture European History The Holocaust European History Figures & Events Wars & Battles European Revolutions Industry and Agriculture History in Europe American History African American History African History Ancient History and Culture Asian History Genealogy Inventions Latin American History Medieval & Renaissance History Military History The 20th Century Women's History View More By Jennifer Rosenberg History Expert B.A., History, University of California at Davis Jennifer Rosenberg is a historian and writer who specializes in 20th-century history. our editorial process Jennifer Rosenberg Updated January 24, 2020 Beginning in September 1941, Zyklon B, the brand name for hydrogen cyanide (HCN), was the poison used to kill at least a million people in gas chambers at Nazi concentration and death camps such as Auschwitz and Majdanek, both in Poland. Unlike the Nazis' earlier methods of mass murder, Zyklon B, which was originally used as a common disinfectant and insecticide, proved to be an efficient and deadly murder weapon during the Holocaust. What Was Zyklon B? Zyklon B was an insecticide used in Germany before and during World War II to disinfect ships, barracks, clothing, warehouses, factories, granaries, and more. It was produced in crystal form, creating amethyst-blue pellets. Since these Zyklon B pellets turned into a highly poisonous gas (hydrocyanic or prussic acid) when exposed to air, they were stored and transported in hermetically sealed metal canisters. Early Attempts at Mass Killing By 1941, the Nazis had already decided and attempted to kill Jews on a mass scale. They just had to find the fastest way to accomplish their goal. After the Nazi invasion of the Soviet Union, Einsatzgruppen (mobile killing squads) followed behind the army in order to round up and murder large numbers of Jews by mass shootings, such as at Babi Yar. It wasn't long before the Nazis decided that shooting was costly, slow, and took too high a mental toll on the killers. Gas vans were also tried as part of the Euthanasia Program and at the Chelmno Death Camp in Poland. This mode of killing used carbon monoxide exhaust fumes from trucks to murder Jews crammed into the enclosed back area. Stationary gas chambers also were created and carbon monoxide was piped in. These killings took about an hour to complete. Test Using Zyklon B Pellets Crematorium 1 at Auschwitz concentration camp. Ira Nowinski/Getty Images Rudolf Höss, commandant of Auschwitz, and Adolf Eichmann, one of the German officers in charge of exterminating Jews and others, searched for a faster way to kill. They decided to try Zyklon B. On September 3, 1941, 600 Soviet prisoners of war and 250 Polish prisoners who were no longer able to work were forced into the basement of Block 11 at Auschwitz I, known as the "death block," and Zyklon B was released inside. All died within minutes. Just days later, the Nazis transformed the large morgue room at Crematorium I in Auschwitz into a gas chamber and made 900 Soviet prisoners of war go inside for "disinfection." Once the prisoners were crammed inside, Zyklon B pellets were released from a hole in the ceiling. Again, all died quickly. Zyklon B proved to be a very effective, very efficient, and very cheap way to kill large numbers of people. The Gassing Process Aerial reconnaissance film of Auschwitz concentration camp, 1st August 1944. Bettmann/Getty Images With the construction of Auschwitz II (Birkenau), Auschwitz became one of the largest killing centers of the Third Reich. As Jewish and other "undesirables" were brought into the camp via train, they underwent a Selektion, or selection, on the ramp. Those deemed unfit for work were sent directly to the gas chambers. However, the Nazis kept this a secret and told the unsuspecting victims that they had to undress for a bath. Led to a camouflaged gas chamber with fake showerheads, the prisoners were trapped inside when a large door was sealed behind them. Then, an orderly, who wore a mask, opened a vent on the roof of the gas chamber and poured Zyklon B pellets down the shaft. He then closed the vent to seal the gas chamber. The Zyklon B pellets turned immediately into a deadly gas. In a panic and gasping for air, prisoners would push, shove, and climb over each other to reach the door. But there was no way out. In five to 20 minutes, depending on the weather, all inside were dead from suffocation. After it was determined that all had died, the poisonous air was pumped out, which took about 15 minutes. Once it was safe to go inside, the door was opened and a special unit of prisoners, known as the Sonderkommando, hosed down the gas chamber and used hooked poles to pry the dead bodies apart. Rings were removed and gold plucked from teeth. Then the bodies were sent to the crematoria, where they were turned into ash. Who Made Zyklon B? Zyklon B was made by two German companies, Tesch and Stabenow of Hamburg and Degesch of Dessau. After the war, many blamed these companies for knowingly creating a poison that was used to murder over a million people. The directors of both companies were brought to trial. Tesch and Stabenow director Bruno Tesch and executive manager Karl Weinbacher were found guilty and given death sentences. Both were hanged on May 16, 1946. Dr. Gerhard Peters, the director of Degesch, was found guilty only as an accessory to homicide and was sentenced to five years in prison. After several appeals, Peters was acquitted in 1955.