A denier argument that gassings did not happen, is the supposed lack of evidence in the Krema roofs, so that Zyklon B could be poured into the Liechenkellers. In this thread, I will gather the evidence of the holes in the Kremas roofs. The Kremas that this applies to are Krema I at Auschwitz main camp and Kremas II and III at Birkenau. There are the three Kremas that had the original corpse storage cellar, the Liechenkeller, converted into a gas chamber.
"On January 29, 1943, Engineer Kurt Prüfer of the Topf firm inspected the sites of the four Birkenau crematoria and wrote a test report, in which he noted the following regarding Crematorium II:
“This building complex is structurally completed except for minor secondary work (due to frost, ceiling of the corpse cellar can not yet be cut out.) The 5 three-muffle cremation furnaces are ready and at present are being dry heat- ed. The delivery of the ventilation unit for the corpse cellar was delayed as a result of the suspension on railway cars, so that the installation can take place no sooner than 10 days from now. Therefore the start of operation of cremato- rium II is certainly possible on February 15, 43.”
There are photos of the work on the Krema II Liechenkeller roof here;
"Eyewitness evidence on the existence and use of the holes:
There are multiple survivor eyewitnesses who described the pouring of Zyklon-B through the small chimneys on the roofs.
Filip Müller, a Slovak Jew who arrived in Auschwitz-Birkenau in April 1942, was put to work in Cremas/Gas Chambers 2 and 3. He recalled the gas chamber room as a long, oblong room with an unusually low ceiling and whitewashed walls. He described the columns below the holes in the roof: “Down the length of the room concrete pillars supported the ceiling. However, not all the pillars served this purpose: for there were others, too. The Zyclon-B gas crystals were inserted through openings into hollow pillars made of sheet metal.” Müller also witnessed the process of inserting the Zyklon-B into the gas chambers from the outside of the building: “The vehicle stopped alongside the lawn behind the crematorium where the concrete shafts projected, through which the pea-sized grains of Zyclon B gas were introduced. Nearby the two ‘disinfecting operators’ were ready and waiting for their orders to pour in the gas crystals.”
Shlomo Venezia, a Greek Jew who arrived in Auschwitz-Birkenau in April 1944, was put to work in the cremas/gas chambers. He recalled: “. . . the German bringing the gas would arrive. It took two prisoners from the Sonderkommando to help him lift up the external trapdoor, above the gas chamber, then he introduced Zyklon B through the opening. The lid was made of very heavy cement . . . The cover was just opened, the gas thrown in, and the cover closed again.”
Henryk Tauber, a Polish Jew who arrived at Auschwitz-Birkenau on January 19, 1943, was assigned to the Sonderkommando in Crema/Gas Chamber 2 in Birkenau. He recalled interior pillars made of heavy wire-mesh “which went up through the roof.” Through the window of the incineration room he observed the process of introducing the Zyklon-B: “Each transport was followed by a vehicle with Red Cross markings which entered the yard of the crematorium . . . They took the cans of Zyklon from the car and put them beside the small chimneys used to introduce the Zyklon into the gas chamber. There, Scheimetz opened them with a special cold chisel and hammer, then poured the contents into the gas chamber. Then he closed the orifice with a concrete cover.” Photographic evidence that testifies to the existence of holes:
In the fall of 1944, Allied planes flew reconnaissance missions over Auschwitz-Birkenau. On August 25, they photographed the four cremas/gas chambers at Birkenau. In the images, the underground gas chamber rooms in Cremas/Gas Chambers 2 and 3 are visible from the outline of the berm of earth and grass that covered them. The chimneys are clearly visible on the roofs of both buildings, as four dark squares are staggered down the length of the roof.
Holocaust deniers claim that these aerial photos have been tampered with and the black marks on the roofs were added later. In 1996, experts at NASA’s Jet Propulsion Laboratory in Pasadena, California, world leaders in the analysis of aerial and satellite images, examined the negatives carefully. The JPL experts found no evidence of forgery or tampering, proving that the markings on the roofs were on the original negative.
The Nazis also photographed the construction work on the cremas/gas chamber buildings. In December 1942, they took a picture of the construction work underway on Crema/Gas Chamber 2. The picture included the roof of the gas chamber room shortly before its completion and before it was covered with dirt. Behind the train’s engine, the four chimneys on the roof and the shadows they cast are clearly visible."