Denial claim: There were no gas chambers. The whole thing is physically impossible.

“There were no gas chambers. The whole thing is physically impossible.”

The gas chambers are in the SS’s own construction files: blueprints, work orders, an invoice for gas-tight doors, and one Auschwitz memo that slips and names a room a Vergasungskeller, a gassing cellar. They are described by the men who operated them and the prisoners forced to empty them. Zyklon-B kills at about 300 parts per million, almost two hundred times below the concentration at which it could explode.

Origin of the claim

The “physically impossible” argument is not new science, it is old advocacy. Its modern form starts with Robert Faurisson, a French literature professor who published “Le problème des chambres à gaz” (The Problem of the Gas Chambers) in Le Monde in December 1978, arguing that no physical trace of a gas chamber survived and that the mechanics of mass gassing made no engineering sense. Faurisson drew on Paul Rassinier, a former Buchenwald inmate turned denier who had questioned the death camps in the 1950s, but Faurisson pushed the claim further, into pure mechanical improbability. The Institute for Historical Review, founded in California that same year, 1978, built an entire publishing operation around the argument, and Fred Leuchter’s 1988 report on Auschwitz and Majdanek, examined on its own page (the Leuchter Report), gave it a veneer of forensic language. None of these men were engineers, chemists or historians with access to the underlying archives. The archives answered them anyway.

The documents

Jean-Claude Pressac, a French pharmacist who spent over a decade in the Auschwitz Museum and Moscow’s captured-German-records archive (RGVA), catalogued the actual paperwork of the SS’s Zentralbauleitung, the Auschwitz Central Construction Office. Among it: architectural plans for Krematorium II and III labeling the underground undressing and gassing rooms, work orders for gas-tight doors (Gasdichte Tür) fitted with small peepholes and rated to withstand the pressure of bodies pressed against them, and invoices for the wire-mesh columns used to drop Zyklon-B pellets into the chamber from the roof. The single most damaging document is a 21 January 1943 internal memo from the construction office referring to a room in Krematorium II as a Vergasungskeller, a gassing cellar, using SS bureaucratic language rather than the camouflage term “special treatment.” Pressac published this material in Auschwitz: Technique and Operation of the Gas Chambers (1989) and Les Crématoires d’Auschwitz (1993). This is not an argument from silence. It is a paper trail the builders themselves left, because they did not expect the war to end the way it did.

The chemistry

Zyklon-B was a commercial pesticide, hydrogen cyanide adsorbed onto an inert carrier, sold before the war by the firm Degesch for delousing barracks and grain stores. Denial literature sometimes implies the gas was too dangerous to deploy around living guards, or that a lethal concentration could not be reached without the chamber exploding. Neither is true. The concentration lethal to a human in minutes is roughly 300 parts per million; the lower explosive limit of hydrogen cyanide in air is around 56,000 parts per million, nearly two hundred times higher. There was no chemical barrier to using the gas exactly as the SS’s own suppliers and camp doctors described using it.

Who testified

The men who ran the killing described it under oath and off the record. Rudolf Höss, Auschwitz’s commandant, confessed at Nuremberg in 1946 and wrote a detailed memoir in Polish custody before his 1947 execution, describing the gassing process at Krematorium II and III step by step. SS camp doctor Johann Kremer’s own wartime diary records witnessing a “Sonderaktion,” using the SS’s own euphemism, in September 1942. In Britain’s zone, the Zyklon-B supplier’s owner, Bruno Tesch, was tried and hanged in March 1946 for knowingly selling the gas for human extermination, the Tesch and Stabenow case. Frankfurt’s Auschwitz Trials of 1963 to 1965 built an independent West German judicial record from surviving guards, camp doctors and the men of the Sonderkommando, the prisoners forced to remove and burn the bodies; several of them, including Filip Müller, later published firsthand accounts that match the SS’s own paperwork in room layout, timing and capacity. None of this evidence needed the others to be true. It converges independently, from adversaries who never coordinated a story: prosecutors, executed defendants, camp architects and prisoners who survived to testify.

Who pushes this claim today

The Institute for Historical Review and the Committee for Open Debate on the Holocaust (CODOH), founded by Bradley Smith, keep the argument alive online, often paired with Germar Rudolf’s self-published “chemical” rebuttals of Pressac, which mainstream forensic chemists have not accepted. The claim also gets state backing: Iran’s government hosted a 2006 Holocaust denial conference in Tehran promoted on its state media, giving Faurisson’s framing an official platform decades after his French convictions for it. On social media the claim resurfaces as “no holes in the roof” memes, a narrower version of the same argument, answered by the fact that Krematorium II’s roof was demolished before its condition could be photographed intact, and by the SS’s own delivery invoices for the wire-mesh introduction columns.

Two killing systems, kept precise where deniers blur them

Honest history does not treat every camp the same. Auschwitz-Birkenau used Zyklon-B; the three Operation Reinhard camps, Treblinka, Bełżec and Sobibor, used carbon monoxide piped from stationary diesel or petrol engines, a different mechanism with its own separate documentary and testimonial record. Denial arguments sometimes blur the two systems together to make either one look shakier by association. They are not the same claim, and the wiki treats them separately for that reason.

Full context: Holocaust Denial, Answered