The Holocaust Historiography Project
Auschwitz, by J.-C. Pressac


(Summary study)

OF BAUWERKEN 5a and 5b (Birkenau I)

The study of “Work sites” 5a and 5b in the first construction stage (Birkenau 1) presents delousing gas chambers using Zyklon-B and shows the evolution of the “disinfestation” techniques used in these buildings.

When Birkenau I was completed it was a matter of urgency to have a delousing installation, like that of Stammlager Block 3. A project drawing of 8/I 1/41 [Drawing 2] was made, showing showers and delousing grouped together, an arrangement that had not been possible initially in the main camp. The prisoners' health situation being catastrophic [Document 1], the only product suitable for drastic measures was one already used. Zyklon-B, which being in the form of a gas had necessarily to be used in a closed space, a “Gaskammer / gas chamber”. The two buildings, BW 5a and 5b had one gas chamber per building, each ventilated by two extractor fans.

As from April 1943 it was envisaged to replace delousing gas chambers by a less dangerous technique, that of hot air disinfestation chambers [Bauleitung drawing 2262 of 8/4/43]. This conversion was concretized on drawing 2540 of 5th July 1943 [Drawing 5]

At present, however, only BW 5b still has a gas chamber in conformity with drawings 801, 1293 and 1715 [Drawings 2, 3 and 4]. Various improvements made to BW 5a and 5b meant that they were fitted with real saunas. Later, the 5a gas chamber was dismantled, the ventilation of the roof modified, the extractor fans removed and the holes filled in. According to drawing 2540 [Drawing 5] two hot air disinfestation chambers of greatly reduced size were installed there, these being the same model as one already operating in the north part of BW 5a, together with an autoclave. This association was to he repeated later in the design of the “Zentral Sauna”, but on a much larger scale.

In B W 5a and 5b, the delousing of the prisoners and their clothing always followed the same pattern. Simplifying the procedure somewhat, the prisoners entered, from left to right on the first two drawings [Drawings 2 and 3], through the windbreak entrance into the “dirty” room where they undressed [Photo 16] and their clothes were taken through the “dirty” anteroom and airlock to the gas chamber. After destruction of the lice using hydrocyanic acid, the effects were once more available to the prisoners, rid of parasites, but still just as dirty. For their part, the prisoners passed under the showers, whose temperature varied according to the whim of the hot/cold water “mixer” on duty, then emerged on the “clean” side and waited for their treated clothes so that they could get dressed again. The overall operation could proceed more or less correctly or he transformed into a nightmare if the Capos or the SS were so inclined.

This modus operandi had a serious fault: the dirty clothes, that had been alive with lice, were given back with the lice dead but the clothes still dirty. Arrangements were made to try to alleviate this problem, the use of autoclaves [Photo 15] and hot air chambers [Photos 12 to 14] making it possible to disinfest and disinfect at the same time, as well as to roughly clean. It should be noted that the introduction of this new system and the sauna meant that the direction of the disinfestation circuit was changed on the last two drawings [Drawings 4 and 5] to right to left, the sequence for the prisoners being: undress / sauna / shower / wait / dress. As for the clothes, it is not possible to state whether they went in the autoclave, then in a gas chamber or were subjected to only one of these treatments.

BW 5a [Photos 9, 10 and 11] and 5b [Photos 6, 7 and 8] each had a delousing gas chamber of 108m² floor area, an enclosed space, separated from the main body of the building by airlocks, with two ventilation outlets in the roof ridge and ventilated artificially by two extractor fans.

A stove, fired from the airlock, i.e. from outside the gas chamber, completed the equipment initially. The part of the building enclosing the gas chamber being separated from the main part of the building and more sensitive to variations in the outside temperature, this single stove was not enough and two others were added [photographic evidence: Photos 6 and 8] The fact is that clothes do not give off natural heat like human beings and in winter it was necessary to heat the gas chamber to reach the point at which hydrocyanic acid evaporates, 26° C. The characteristics of a traditional and “home-made” delousing gas chamber in KL. Auschwitz can be defined as follows:

  • Room separated from others by one, or two airlocks:
  • An extractor fan for ventilation:
  • One or more stoves to obtain the hydrocyanic acid vaporization temperature:
  • The openings:
    • The doors and windows being of normal construction, they had to be sealed by sticking strips of paper over the cracks:
    • Gas-tight doors could be installed, gas-tightness being achieved by fixing felt sealing strips on both the door and the frame and a light fit being ensured by two angled bolts being screwed into the catches in which the latch bars were housed.

After the transformation of BW 5a, the path taken and the introduction of hot air by forced draught into the disinfestation chambers are clearly indicated. The source of the hot air, on the other hand is not known and the generators are not mentioned. It can be assumed that it either came from the main boiler house or that there was a separate heating system connected with the blower system, near to the disinfestation chambers. [Photo 17]

In the two delousing gas chambers of BW 5a and 5b there appeared in the course of time a bluish coloring of the walls, known as the “blue wall phenomenon”, which permits the immediate distinction on sight between delousing and homicidal gas chambers. The delousing and homicidal installations where hydrocyanic gas was used were of strictly identical design: a closed space of any desired volume with one or two gas-tight or temporarily sealed doors and fitting with one or two fans for ventilation (sometimes natural ventilation only). Their method of use was radically different. Lice are less susceptible to the toxicity of hydrocyanic acid than is man. A hydrocyanic gas concentration of 0.3g/m³ (lethal dose) is immediately fatal for man, while in order to destroy lice a concentration of 5 g/m³ applied for at least to hours is necessary. If this concentration is maintained for 6 hours, all insects are destroyed [source: Degesch]. In Birkenau, the quantity poured into the homicidal gas chambers was forty times the lethal dose (12 g/m³) which killed without fail one thousand people in less than five minutes. Afterwards the fans were switched on or the natural ventilation started. Then came the cremation of the corpses over a period of 24 hours (in Krematorien II and III). The contact time for the hydrocyanic acid with the walls of the homicidal gas chambers never exceeded about ten minutes per day at a temperature below 30 degrees Celsius. In the clothing delousing gas chambers a minimum concentration of 5 g/m³ was used during several cycles per day, the duration of the cycle varying according to the contact time chosen. This hydrocyanic saturation for 12 to 18 hours a day was reinforced by the heat given off by stoves (situated in the chamber) providing a temperature of 30 degrees Celsius. The walls were impregnated with warm hydrocyanic acid for at least 12 hours a day, which was to bring about in situ the formation of a dye, “Prussian blue” or potassium iron (III) hexacyanoferrate (II), whose composition varied according to the conditions of formation, The bluish coloring of the walls, [Photo 18], internal and external [Photos 6 to 11] was not visible at the liberation of the camp, but appeared in subsequent years, under the influence of various physico-chemical factors which have not been studied. The “blue wall” phenomenon makes is possible now to distinguish visually, empirically, but with absolute certainty, between delousing gas chambers, where the phenomenon is present, and homicidal gas chambers where it is not. Without additional heat the too brief contact of nevertheless high concentrations of hydrocyanic acid with the walls of the homicidal installations was not able to provoke a development of the reaction appreciable enough to be visible.