The Crematoria Ovens of Auschwitz and Birkenau

By Carlos Mottogno


If a monstrous extermination of many hundreds of thousands of people took place in gas chambers in Auschwitz and Birkenau during the Second World War, and if the bodies of the victims were disposed of in the cremation facilities in those camps, then the ‘murder weapon’ – the homicidal gas chamber – has an essential counterpart: the cremation oven.

The ‘eyewitnesses’ have tried to persuade us that the crematoria ovens of Auschwitz and Birkenau were satanic contraptions operating above and beyond the realm of physical laws,6 not ordinary cremation facilities subject to the same laws of chemistry, physics and heat engineering as all other such installations. Historians have chosen to trust blindly in these witnesses, and in the process have let themselves get carried away into making entirely erroneous claims.7

Aside from the Revisionists, Jean-Claude Pressac is the only researcher to have approached the historical problem of the cremation of bodies in Auschwitz and Birkenau from a technical perspective. In his book Auschwitz: Technique and Operation of the Gas Chambers 8 he comes to the following conclusions:

• The three double-muffle ovens in crematorium I of Main Camp Auschwitz had a capacity of 340 cremations in a 24-hour period.9 In 1993, he reduced this figure down to 200-250 per day.10

• The five three-muffle ovens in crematoria II and III of Birkenau each had a maximum capacity of between 1,000 and 1,500 cremations per 24 hours,11 but their normal capacity was 1,000 to 1,100 cremations each per 24 hours.12 In 1993, he reduced this figure down to 800-1,000 per day.13

• The two eight-muffle ovens of crematoria IV and V each had a capacity of 500 cremations per 24 hours.14

Pressac thus puts the total capacity of the crematoria of Auschwitz and Birkenau at 3,540 cremations per day. From a technical perspective this figure is completely unrealistic.15 Among the Revisionists it was particularly Fred A. Leuchter who, in his well-known Leuchter Report, 16 turned his attention to the issue of the cremations. Relying primarily on the statements of Ivan Lagacé, the manager and operator of the Bow Valley Crematorium in Calgary, Canada,17 Leuchter erroneously arrived at a figure of 156 bodies per day as the total cremation capacity of the crematoria of Auschwitz and Birkenau. This figure is actually far below the actual capacity.

Pressac and Leuchter arrived at conclusions which, though diametrically opposed, are equally unfounded because no serious, fundamental studies have been conducted of the crematoria ovens at Auschwitz and Birkenau, whether by the orthodox historians or by the Revisionists. We intend to close this debilitating gap.

The Technology of Crematoria Ovens Up To World War One

The cremation of dead bodies was practiced in Europe for more than a thousand years before Homer’s time. 18  This custom was carried on until 785 AD, when Charlemagne forbade it, on pain of death, in his Decree of Paderborn.19 In the following centuries cremation disappeared from christian Europe. The idea of cremation regained some popularity during the French Revolution, but it was during the second half of the 19th century before it gradually found general acceptance.20

The trend favoring cremation began to gain momentum in 1849, when the philologist Jakob Grimm gave a memorable lecture “on the cremation of corpses” 21 at the Berlin Academy of Sciences. The idea was quickly taken up by eager pioneers, and enthusiastically promoted.22 The first cremation in a crematorium oven in Europe took place on October 9, 1874 in Dresden, in a makeshift oven designed by Friedrich Siemens. After a few cremations this experimental procedure was banned by the Saxon government.23 In those years, Italy was leading this modern movement for cremation, both legally and technologically. The first European crematorium was built in Milan in 1875, one year after cremation was recognized as a legal method for the disposal of the dead.24 The first German crematorium was put into operation in Gotha on December 10, 1878. This period saw a great fervor of studies and experiments that led to the construction of several types of furnaces. Modern cremation had to satisfy certain ethical, aesthetic, and economic requirements, which were defined during a general conference on cremation technology held June 7, 1876 in Dresden.

Many cremation facilities of the 1870s were as yet very unreliable and costly to operate – some had cremation times of up to 5-6 hours per corpse –, so that some were torn down again after just a few cremations. But much better capacities and fuel efficiencies were quickly reached: The Gorini oven at Riolo, for instance, which started operation on September 6, 1877, needed only 100-150 kg (220- 330 lbs) and 1.5-2h per corpse. The oven by Toisoul and Fradet needed ca. 100 kg and just one hour per corpse.25 In these ovens, the body was directly exposed to the flames, which were produced either by the incineration of the fuel or by combustion of the fuel gases from the gas generator. A principle devised by Friedrich Siemens introduced the process of wholly indirect cremation using heated air, allowing only hot air but no flame gases to reach the body. This method predominated unchallenged in Germany until 1924. In this new procedure, cremation was performed by means of air heated to 1000C (1830F) in a regenerator or recuperator.26 The experimental prototype of such an oven was installed in 1878 in Gotha and was used for the cremation of animal carcasses only. A cremation took 135 minutes on average; the first cremation required 1,500 kg (3,300 lbs) of brown coal, subsequent ones took from 250 to 300 kg (550 to 660 lbs) or less, with the requirements decreasing step by step.27

The Swedish Klingenstierna oven was a distinct improvement over the Siemens oven. Besides a main firing, it had a secondary firing that served mostly to burn off the remaining gases and smoke particles; the combustion air was heated in a recuperator consisting of metal baffles (heat exchanger between the furnace gas and the combustion air); the body was introduced into the incineration chamber on a small cart that remained there for the entire duration of the cremation cycle. In Germany this system was perfected by E. Dorovius and built by the firm of Gebrüder Beck in Offenbach. The first models, which were installed in the crematoria of Heidelberg (1891) and Jena (1898), still retained a cart for introduction of the body, but the 1899 model (Offenbach crematorium) worked without a cart, and the incineration chamber was replaced by a grating of refractory grilles beneath which two sloping surfaces angled like a funnel channeled the ash into the ash pit.28 The metal type of recuperator was gradually replaced by one with refractory brick, and the oven took on the typical structure of the German crematoria ovens with coke-fired gas generator.

A prototype of the Schneider furnace was installed in the crematorium of Hamburg in 1892. Its structure was similar to that of the Klingenstierna-Beck oven with some improvements to the gas generator. It took approximately three hours to get this oven to an operational temperature. The duration of a single cremation was between 45 and 90 minutes, with a coke consumption of 250-300 kg (550-660 lbs) for the first and 50-100 kg (110-220 lbs) for subsequent cremations. The Ruppmann furnace had already the typical structure of a modern coke-fired crematorium oven.29 According to experimental data taken at the crematorium of Stoccarda during 48 cremations between July 20 and September 15, 1909, a cremation lasted in average 1h 33min, with a minimum of 1h 10min and a maximum of 2h 30min.30 The oven designed by the Swedish firm Knös introduced some more improvements to the Klingenstierna-Beck system. Its coke consumption for the heating and the first incineration was 300 kg and 50-90 kg for each subsequent cremation. In Germany, the company Gebrüder Beck of Offenbach produced this oven under a license contract.

Technological Progress and Developments in the Inter-War Years

After the First World War, the peace dictate of Versailles forced Germany to give up coal-rich regions as well as to supply coal to the victorious powers. Hence, Germany saw herself forced to use the coal reserves left to her as efficiently as possible. For these reasons, German industry endeavored to redesign, in terms of heat engineering, all facilities consuming coal and coal products so as to maximize the return achieved per unit of fuel consumption. Crematoria ovens and their operation were by no means exempt from this need for the thrifty use of coal. Consequently, a Prussian law dating from September 14, 1911 was amended in 1924; this law had permitted only the wholly indirect cremation of bodies, for aesthetic reasons, but this process required more time and fuel than its alternative.31 The debate about this amendment was accompanied by at times heated arguments among the cremation experts, disputing which of the two methods was the more economic one.32 This question could be resolved only by means of scientific cremation experiments.

The most significant experiments of this period were carried out in 1926 and 1927 in the crematorium of Dessau by the engineer Richard Kessler, who also wrote a detailed scientific report on the subject.33 In the following we shall examine the results of these experiments. The construction method of the new ovens took into account the decisive factors involved in the optimum use of combustion heat that engineer Kessler had discovered in his experiments. As a result the efficiency of the oven increased considerably. The most important technological innovations of that time include the reduction of the horizontal cross-section of the gas generator; more efficient recuperators; the installation of an after burning grate; an air intake system to allow for more efficient after burning; and the installation of appropriate measuring instruments.34 In the early 1930s the coke-fired ovens with gas generator had reached the pinnacle of technological perfection, yet at the same time their inexorable decline began as they were being increasingly supplanted by significantly more economic heating systems, particularly ones using gas and electricity. From this point on, the existing coke-fired ovens were either torn down 35 or restructured to accommodate gas heating.36 The new heating systems necessitated additional studies on the structure of the ovens as well as on the phenomenon of cremation per se, and these studies were presented in significant technical publications.37

Even though the first German crematorium had already been built in 1878, cremation was not legally permitted until 1911 and it took until the 1930s before formal legislation on this matter actually appeared. The first real and complete Cremation Act was passed on March 15, 1934. Specific guidelines pertaining to the cremation ovens and the cremation process followed soon thereafter.38 As the following table shows, the number of cremations in Germany rose astronomically between the time when the first crematorium was opened, and the beginning of the Second World War: In 1938, 84,634 cremations were performed in 120 crematoria; 40 in 1939 there were 102,112 cremations; in 1940, 108,130; in 1941, 107,103; and in 1942, 114,184.41

J. A. Topf & Söhne, Erfurt

Where crematoria ovens are concerned, the firm of J. A. Topf & Sons of Erfurt began manufacturing operations at the start of the First World War and was most notably successful in the early 1920s.42 Their early models pioneered several innovations, particularly a system of exterior muffle heating, based on a patent by Max J. Kergel. 43 This prevented the cremation products from entering the muffle, thus allowing for an entirely indirect cremation process.
This cremation oven consisted of a coke generator; a self-contained cremation chamber (muffle); a system of baffles underneath (recuperator), which served to preheat the air required for the cremation; and the diversion of the carbon monoxide gases around the muffle.44 The ovens built during the 1920s needed 60 to 75 minutes and consumed some 160 to 260 kg (350 to 570 lbs) of coke per cremation.45

During the 1920s, the firm of J. A. Topf & Sons became Germany’s foremost commercial oven manufacturer. Between 1922 and 1927, no less than 18 of the 24 ovens installed in the German crematoria were built by Topf.46 In the early 1930s Topf’s commercial supremacy was consolidated.47 By now Topf & Sons had achieved a very advanced technological level. They deserve the credit for designing Germany’s first fully functional gas-heated cremation oven (1927, in Dresden), as well as the country’s first electric cremation oven, which came into service in Erfurt in 1933. The firm also pioneered improvements in cremation technology such as the afterburning grate and the rotating grate.

Even though the electric Topf ovens had no competition in Germany, the company’s supremacy in the oven manufacturing field was seriously threatened in those years by the newly developed gas oven of the Volckmann-Ludwig type.48 In technological respects, the Topf firm responded to the competition posed by the new oven by designing a Model 1934 gas oven.49 In propagandistic terms they responded with rather harsh polemics in the form of a most aggressive article by engineer Kurt Prüfer, 50 the man who would design the three- and eight-muffle ovens of Birkenau; the criticism advanced in that article, however, was refuted by Richard Kessler. 51

Structure and Operation of coke-fired cremation ovens of the 1930s

This type of furnace consisted of a gas generator, an incineration room or muffle, a post combustion chamber below it, and a recuperator thereafter. The gas generator, lined with refractory material, had the usual grill for the coke and openings to regulate air intake and to remove ashes and cinders. A vertical or oblique channel conducted the combustion gases into the muffle. As a result of lack of oxygen, the coke burnt only partly in the gas generator, producing carbon monoxide rich gases which were led into the muffle, where it burnt with additional pre-heated air coming in from the recuperator. The muffle was a horizontal combustion chamber lined with refractory material.

The German “Norms for the construction and operation of furnaces for the cremation of human corpse” enacted
in 1937 prescribed the following minimal measures for such a muffle: width: 900 millimeter; height: 900 millimeter; length: 2500 millimeter.52 At the front, the muffle was closed with a guillotine-like shutter made of fireclay. In front of this shutter was an outer metal door. The bottom of the muffle consisted of a grill made of fireclay, on which the coffin was placed. The remains of the body fell through the refractory grilles into the postcombustion chamber with slanted walls narrowing down to a small cavity in which the container for the ashes was placed. Openings in the post combustion chamber led the combustion gases into the recuperator, which is a heat exchanger consisting of intertwined, counter-current fresh-air intake and exhaust gas exit channels. As a result of this heat exchange, the recuperator had temperatures between 400 and 600°C.

The oven was a two-level structure: the gas generator and recuperator were at a lower level, while the incineration chamber was at an upper level. The operation of this system was as follows: First, the shutter of the smoke flue was opened. Then, the coke fire in the generator was lit with the help of some wood. As soon as the combustion gases burning in the muffle had increased the temperature to an operational level, the introduction shutter was opened and the coffin was introduced in the muffle. Because of the high temperature of the muffle, the coffin caught fire already during the introduction. It burned quickly, leaving the corpse on the grill. First, the corpse dehydrated, then the combustible parts incinerated. The solid incineration products of the corpse fell into the post-combustion chamber and ultimately into the ash container, while the gaseous products moved into the side flues of the recuperator and down through them into the waste-gas flue, whence they rose up the stack. When the flame development had stopped, the incandescent ashes were scrapped into the ash container. The oven was operated with the help of various controls (fuel supply, recuperator and generator air intake, exhaust shutter).53

The Coke Consumption of a Cremation Oven with Coke-Fired Generator

A cremation oven’s fuel consumption depends in the main on the manner of the oven’s construction, the cremation process, the frequency of cremations, the state of the bodies, and the operation of the oven. For this reason it is pointless to speak of an oven’s fuel consumption without considering at least the following three factors: the oven’s construction system, the manner of cremation (direct or indirect), and the frequency with which cremations are carried out. The procedure involved in indirect cremation is much more fuel-intensive than that of direct cremation, since the former requires that the entire fireproof mass of the recuperator be heated to 1000C (about 1830F). The frequency of cremations has a very significant effect on fuel consumption, since the oven’s firebrick absorbs most of the heat generated during the first cremations. For this reason fuel consumption is lowest when the oven is operating at thermal equilibrium.

The heat balance of a cremation oven with coke-fired generator is a problem, very difficult to resolve in theory, since in practice the performance is affected by variable factors which cannot be predicted by theory and which affect the operation of the oven from case to case. In the 1920s this problem was discussed by scientists like Fichtl 54 and Tilly, 55 but the most important contribution to its resolution was Wilhelm Heepke’s 1933 article on this subject.56
Heepke’s calculations showed that the per-cremation coke consumption of a medium-sized oven at thermal equilibrium amounts to 30 kg (66 lbs) of coke (plus the wooden coffin weighing 40 kg, or 88 lbs). However, Heepke’s findings are marred by errors both in approach and in arithmetic, and his conclusions are thus questionable. If one takes his errors into account, one arrives at a coke requirement of 20.5 kg (45.1 lbs). This result is consistent with those of experimental origin. The experiment conducted by R. Kessler with coke fuel on January 5, 1927, indicated the following fuel consumption:

• total consumption: 436.0 kg (960 lbs) coke
• preheating of the oven: 200.0 kg (440 lbs) coke
• 8 successive cremations: 236.0 kg (520 lbs) coke
• consumption for 1 cremation, including preheating: 54.5 kg (120 lbs) coke
• consumption for 1 cremation without preheating of the oven: 29.5 kg (65 lbs) coke

The fuel consumption relating to the eight cremations exclusive of the preheating of the oven still includes the consumption producing the heat that is absorbed by the oven’s firebrick up to the point where thermal equilibrium is reached. A calculation to take into account the heat loss caused by radiation and conduction shows that the coke consumption for a cremation in an oven at thermal equilibrium is about 20 kg (44 lbs). This confirms the correctness of this method of calculation, which can thus also be used to determine the thermal balance of the cremation ovens of  Auschwitz and Birkenau.

The Duration of the Cremation Process with a Coke-Fired Generator

Cremation is a physical and chemical process requiring a certain minimum time that cannot be decreased further.57 This minimum time depends in the main on the chemical composition of the body to be cremated. As special experiments conducted in England in the 1970s showed, the body’s protein structure is of great importance. Due to its relatively high nitrogen content, its high ignition temperature and the chemical transformations which the proteins undergo at high temperatures, there is a considerable degree of resistance to combustion, which is amplified further by the fact that the protein substance is submerged, as it were, in body fluid and cannot ignite before this fluid has evaporated. In other words: A cremation carried out under optimum conditions cannot take less time than the time perforce required for this process to take place. Conversely, the duration of the cremation cycle increases, of course, the more that actual conditions are removed from the optimum, regardless of whether this discrepancy is due to careless operation of the oven or to a less-than-ideal oven construction system.

Before raising the question of the length of the cremation process or the cremation cycle, we must clarify just exactly what we mean by that. In very general terms, we can say that a cremation is completely finished once the ashes remaining of the body have been removed from the oven. For an oven not equipped with an afterburning grate, the cremation time may be defined as the time between the introduction of the coffin into the muffle and the transfer of the glowing ashes from the ash slope into the ash container, in which they gradually collapse altogether. In an oven equipped with an afterburning grate, such as the generator ovens of Beck and Topf and the Volckmann-Ludwig gas ovens of the 1930s, the end of the cremation process is set as the time at which the glowing ashes are removed from the ash slope or transferred from the bottom of the muffle to the afterburning grate. Even though it violated the ethical norms set by R. Kessler in 1932, it was common practice in some crematoria to introduce the next body into the muffle while the remnants of the previous still burned on the ash slope, so that one oven actually contained two bodies at the same time, albeit at different stages of the cremation cycle. This process was used in ovens such as the Volckmann-Ludwig type in Stuttgart, which were equipped with a damper in the ash settling chamber.

As we have already mentioned, scientific experiments were carried out in England in the 1970s to determine which factors influence the cremation process. The results were announced in July 1975 at the annual conference of the Cremation Society of Great Britain. The experiments were grouped into two series: an introductory series in Ruislip’s Breakspear Crematorium and the main series in Hull’s Chanterlands Crematorium. The first group of project leaders selected the factors that, in their opinion, would affect the length of the cremation process. The influence of technical factors was equalized by using the same gas-fired oven (Dowson & Mason Twin Reflux Cremator) and the same heater for all experiments.58 On the basis of these experiments it was found that the truly decisive factor, where the time required for a cremation is concerned, is the maximum temperature of the oven. Statisticians graphically summarized the results of the experiments. One of the analysts, Dr. E. W. Jones, commented as follows:58 “From his graph he was able to tell us (we thought this rather interesting) that there is a maximum point, or rather a minimum point, of incineration time below which it is impossible to go, and our statistician defined this as a thermal barrier that, because of the make, the nature of human tissues, you cannot incinerate them at a rate which is below round about 63 minutes. Now some people will come up with readings of 60, 59, 58, they are the lower ends of this scatter of readings, and that this thermal barrier’s optimum temperature is round about 800-900C.” The graph shows that the time that most closely approximates the thermal barrier is 60 minutes, given a temperature of 800C (1470F). If the temperature is increased to 1000C (1830F), the time required for cremation increases to 67 minutes, and at 1100C (2010F) it drops again, to 65 minutes. At higher temperatures, which were not investigated, the time would presumably decrease further, and at extremely high temperatures it probably drops below the thermal barrier. Dr. Jones stated that if one wanted to decrease the cremation time in this way to 20 or even to 15 minutes, one would have to construct an oven capable of working at 2000C (3630F).58

In reality, the cremation process must take place between fairly precise thermal boundaries. At temperatures of over 1100 to 1200C (2010 to 2190F) one encounters the phenomenon of sintering, where the bones of the corpse and the oven refractory begin to soften and to melt together (fuse), and at temperatures under 700 to 600C (1290 to 1110F) the body merely chars.59 Dr. E. W. Jones then reports an observation of particular interest to us:58 “Our statistician colleague did some work, he looked into the records of crematoria in Germany during the last war, and it would appear that the authorities there were presented with a similar problem – that they came up against a thermal barrier. They could not design a furnace that reduced the mean incineration time to a very practical effective level. So we started to look at why there is this thermal barrier with human tissues.” It was found that the cause of this factor was that the proteins in the human body – when they are heated to 800 to 900C (1470 to 1650F) – undergo a chemical transformation. They dissociate and form compounds “that can only be described as a hard crust.” 58

Naturally the cremation process took longer in ovens operating with a coke-fired gas generator. Regarding the time required for the cremation cycle, the data to be found in contemporaneous literature is almost never entirely reliable, first and foremost because what is meant by ‘the time required’ is very rarely clearly defined, and secondly because one must expect that the data have been distorted for reasons of competition or propaganda. This is why we shall take data supplied by the technical measuring instruments in the ovens themselves as our objective and incontrovertible starting point. From this perspective, the diagram summarizing the cremations performed by R. Kessler with coke fuel on January 5, 1927, is especially significant. This was a case where one is completely justified in saying that the cremations were carried out under the optimum conditions for an oven with a gas generator, because:

• the construction system of the oven was excellent;
• Kessler had taken every measure necessary to prepare the oven in terms of heat engineering;
• the appropriate technical instruments were used to observe the cremation cycle in every phase;
• under the knowledgeable supervision of an expert engineer the operation of the oven went off
especially smoothly.

During these experiments the average cremation time was 1 hour and 26 minutes, while the shortest cremation took 1 hour. The average temperature in the muffle was about 870C (1600F). We shall return to this point later. In this context it is important to stress that engineer Kessler was using the method of direct cremation. For comparison we refer to a different series of eight cremations that Kessler performed in the same oven, using briquettes instead of coke fuel. That time the average cremation took 1 hour and 22 minutes. Two weeks later the same experiment, using gas heating for the oven, returned an average cremation time of 1 hour and 12 minutes for each of the eight cremations.60

The Topf Cremation Facilities for Concentration Camps

As of the late 1930s, Topf & Söhne as well as other manufacturers, especially the firm of H. Kori in Berlin and the Didier-Werke (also in Berlin),61 began to design cremation ovens for the concentration camps. These ovens were constructed more simply than those for civilian use. The Topf firm developed six projects for cremation ovens of this type:

1. Coke-fired single muffle oven, never built.62

2. Mobile, petrol-fired two-muffle oven, later converted into a stationary coke-fired oven. This type of oven was installed in Gusen (a subcamp of Mauthausen) and Dachau. The first one was ordered by the SS-Neubauleitung of the Mauthausen camp on March 21, 1940, as a mobile, petrolfired oven (“fahrbarer Ofen mit Ölbeheizung”), but on October 9, 1940, it was decided to convert it into a coke-fired oven.63 Topf shipped the oven by railroad on December 12, 1940, and it arrived at its destination on December 19.64 This same day, the SS-Neubauleitung of the Mauthausen camp sent a telegram to Topf with an urgent request for an engineer.64 The Topf firm sent its engineer August Willing to Gusen on December 27,65 who immediately began his work and finished it on January 22, 1941. The two coke-fired gas generators had been installed during the construction of the oven, which went into operation at the end of January 1941.66 According to a Topf letter to the SS-Neubauleitung of Dachau of July 25, 1940,67 the oven of the Dachau camp had been delivered even earlier. The SS authority of the Dachau camp decided also to convert this oven’s heating system by replacing the two petrol burners with coke gas generators. Both converted ovens do still exist today in these former concentration camps. Initially, the decision of local authorities to convert the heating system of certain crematorium ovens was prompted by the sheer lack of liquid fuel, but on December 17, 1943, the Chief of Amt CIII (Technische Fachgebiete) of the SS-WVHA sent an executive order stating:68 “In the crematoria, the use of liquid fuel can no longer be permitted. The modification to solid fuel has to be done everywhere.”

3. Coke-fired two muffle oven, installed at Buchenwald camp. On June 18, 1938, the Construction Office of the SS administration of Buchenwald-Sachsenhausen camp sent a request to SSGruppenführer Eicke, head of the Totenkopfverbände and of the concentration camps, to authorize the construction of a crematorium at the Buchenwald camp. Eicke forwarded this request to the Head of the SS administration in Munich with a note in which he endorsed the request since, as a result of an increased number of inmates of this camp, Buchenwald was confronted with deceased inmates almost on a daily base, whose bodies had to be cremated in the municipal crematorium of Weimar.69 The request was welcomed and the authorization was released by the Hauptamt Haushalt und Bauten (HHB) at the beginning of December 1939. For the construction of an “emergency crematorium” (Notkrematorium), as it is referred to in German administrative documents, a request was sent to the firm Topf. On December 21, 1939, Topf sent an estimate to the appropriate authorities for “1 petrol- or coke-fired Topf incineration oven with double muffle and compressed-airblowers, as well as forced-draft blowers” for 7,753 RM, plus 1,250 RM for the installation.70 The “Description of the structure of the new construction of an emergency crematorium in the detention camp Buchenwald” specifies:71 “Due to the high mortality rates in the Buchenwald camp, the construction of an emergency crematorium with petrol-fired cremation oven (double muffle oven) has become necessary. For this, a location of 6 x 9 m and 4 m height is required.” In its estimate of December 21, 1939, the Topf firm also included a drawing of the oven, edited the same day,72 and a plan for a small crematorium of just 6 m × 9 m × 4 m.73 The document just quoted refers to this small crematorium and contains a “cost calculation”, a “recapitulation of the costs” and finally a “calculation of the masses” of the emergency crematorium for the Buchenwald camp, whose cost was estimated to 14,200 RM.74 No documents regarding the realization of this project are known to me. A later, undated project, probably from 1940, shows a more sophisticated crematorium with outer dimensions of 14 m × 12 m, consisting of five rooms. The furnace room (6.50 m × 4.99 m), however, contains only one single muffle oven.75 According to Kurt Prüfer, a Topf two-muffle oven was installed at Buchenwald in 1940-1941,76 which evidently was the subject of the estimate mentioned above.

4. Coke-fired two muffle oven type Auschwitz. Three ovens of this type were built in the crematorium of Auschwitz I between 1940 and 1942; one was built in 1945 in the crematorium of Mauthausen.

5. Coke-fired three muffle oven. Two ovens of this model (one also equipped for petrol-firing) were installed in the crematorium of Buchenwald in 1942, two in the crematorium of Groß-Rosen in 1942,77 and ten in the crematoria II and III of Birkenau in 1942-1943.

6. Coke-fired eight muffle oven. Two ovens of this type were built in the crematoria IV and V of Birkenau in 1942-1943, and one half of such an oven (4 muffles) was installed at Mogilew in 1942. The ovens of Auschwitz will be described in the following paragraphs.

The Coke-Fired Topf Double-Muffle Cremation Ovens

As far as we know, Topf built four ovens of this type, of which three were installed in crematorium I, the old crematorium of Main Camp Auschwitz, while the fourth was located in the crematorium of Mauthausen. Work on building the first oven for Auschwitz began in early July 1940. A September 16, 1940 letter from the Auschwitz Administration reveals that the oven had been “in service for weeks already”.78 One can thus assume that the oven was first put into service around the end of July 1940. It was built between July 5 and 25, 1940, and the first cremation took place on August 15.79 The cost estimate for the second oven is dated November 13, 1940. The Topf firm delivered the various components of the oven to Auschwitz on December 20 and 21, 1940 and January 17 and 21, 1941.80 It was constructed between January 26 and February 22, 1941.81 Topf revised its cost estimate for the third oven on September 25, 1941,82 and sent the required material to Auschwitz on October 21, a total of 3,548.5 kg.83 Construction of the foundation for the third oven began on November 19, 1941, and was completed on December 3;84 work was then discontinued due to a lack of fireproof material. The pertinent invoice issued by Topf is dated December 16, 1941.85 Due to a Waggonsperre (railroad car prohibition86), however, construction of the ovens could not start because the Collmener Schamottewerke, supplying Topf with refractory material, had not been able to deliver the required material. The railroad freight car with the refractory material, sent from the Plützsch firm, arrived at the camp on January 3, 1942,87 but this oven was built in March 1942. 88

The oven for Mauthausen (near Linz, Austria) was ordered from the Topf firm on October 16, 1941, but the SS Office for Construction Management hesitated for a long time before having it built. The components of the oven were shipped to Mauthausen between February 6, 1942 and January 12, 1943,89 but the decision to assemble it was not made until late 1944.90 The oven was finally built in January-February 1945, which explains the fact that it is relatively well preserved. The two Topf double-muffle cremation ovens presently on display in the crematorium of Auschwitz Main Camp were reconstructed after the war, but in a rather awkward manner, using original parts that had been removed from the ovens by the SS. It is thus entirely pointless to examine these reconstructions in the hopes of gaining an understanding of this type of oven. For this reason our investigation is based wholly on the examination of the oven from Mauthausen, and on the documents available to us relating to the ovens of Auschwitz and that of Mauthausen – all of which were the same model.91 The components of the oven of Mauthausen are also included on Topf’s shipment list of January 12, 1943.92 The construction of the double-muffle cremation oven is shown on diagram “Topf D57253”, which dates from June 10, 1940 and refers to the first oven built in Auschwitz. The oven is solid brick and sealed with a row of wrought-iron anchors. The dimensions of the Mauthausen oven are virtually identical to those shown on diagram D57253, which correspond to the measurements of the anchor irons itemized on Topf’s shipment list of January 17, 1941 with respect to the second oven of Auschwitz. The oven is equipped with two cremation chambers, or muffles.93 The oven’s operation is explained in the “Operation Manual for the Coke-Fired Topf Double-Muffle Cremation Oven.” 94

The crematorium of Auschwitz was originally constructed in accordance with diagram “Topf D50042” of September 25, 1941, which had been drawn up for the construction of the third oven.95 Each oven was equipped with its own forced-air installation; this consisted of an air blower, which was operated with a 1.5 hp three-phase AC motor coupled directly to the blower shaft, and an appropriate duct. The square stack originally had an area of 500 × 500 mm2 (19.7″ × 19.7″). The exhaust installation, with a capacity of about 4,000 m3 /h (141,200 cu.ft./h) of stack gas, consisted of an exhaust fan powered with a 3 hp three-phase AC motor coupled directly to the blower shaft; an air shutter separated the high and low pressure chambers. The function of this installation is described in the relevant operation manual from the Topf firm.96 The oven loading system was made up of a carriage via which the body was introduced into the muffle. This conveyance consisted of a carriage, which moved on special rails and on which the coffin was introduced, and of a shunting carriage running above it. On July 19, 1943 the crematorium was taken out of service,97 and the ovens were then dismantled. After the end of the war the Poles reconstructed ovens 1 and 2, for which purpose they used the original parts which had been removed by the SS and of which many were still in the former coke fuel storage room. The reconstruction was done in a remarkably slipshod manner, and the ovens would not be functional in their present state.

The Coke-Fired Topf Three-Muffle Cremation Ovens

Just like the eight-muffle oven, this oven was designed by engineer Prüfer during the last months of 1941. On October 22, 1941 the Central Construction Office of Auschwitz ordered from the Topf firm, five Topf three-muffle ovens with forced-air blower, for the new crematorium, which the Office intended to construct in the Main Camp. These ovens were later installed in crematorium II of Birkenau. The final bill for this was dated January 27, 1943, and the cost per oven was RM 6,378.98 The five three-muffle cremation ovens for crematorium III were first ordered by the Central Construction Office on September 25, 1942, by telephone, and on September 30 by registered letter.99 On October 28 the Topf firm sent the Central Construction Office diagram D59394 for the construction of the ovens in crematoria II and III. This diagram has been lost.100 The final bill for the five three-muffle cremation ovens for crematorium III of Birkenau is dated May 27, 1943. The cost per oven was RM 7,830.101

The first two three-muffle ovens supplied by Topf went into service in the concentration camp Buchenwald, on August 23 and October 3, 1942.102 The following description of the Topf three-muffle cremation oven is based on direct examinations of the ovens of Buchenwald and on the documents available. Three photographs from SS sources 103 confirm that the three-muffle ovens installed in crematoria II and III of Birkenau were the same model as those in Buchenwald; one of these, however, could also be fired with fuel oil.

Regarding its construction, the three-muffle oven consisted of an oven with two muffles, each with one coke gas generator, and an additional third, central muffle and other technical modifications, which we have already set out elsewhere.2 The oven is contained within a solid brick structure with fittings of wrought and cast iron. Considering that the fireproof brickwork of the double-muffle cremation oven of the type installed at Auschwitz weighed about 10,000 kg (22,000 lbs),104 it is clear that the three-muffle oven was a more economical facility, as one can also deduce from the considerably lower price. The third double-muffle oven of Auschwitz cost RM 7,332 and included a forced-air blower and a conveyance, with the appropriate rails, to introduce the body into the muffle.

The ovens of crematorium II of Birkenau cost RM 6,378 each and included a forced-air installation. Considering that two body conveyances and the rails for five ovens cost RM 1,780, the three-muffle oven with the same equipment actually cost less than a double-muffle oven. The unit price for the ovens for crematorium III, on the other hand, was a little higher (RM 7,380, without the body conveyance), but still much more reasonable. Crematoria II and III of Birkenau had a large oven room measuring 30 m × 11.24 m (98.4′ × 36.9′). The five three-muffle cremation ovens were located along the longitudinal axis. Adjoining the oven room was a crematorium wing 10 m × 12 m (33′ × 39′) in size and split into two sections by a dividing wall. The smaller section directly adjoining the oven room was in turn subdivided into three rooms: two engine rooms and a room for one of the three exhaust installations with which the crematorium was equipped. The other section contained the stack, the other two exhaust installations and a trash incinerator, which is why this room was labeled “trash incinerator” on the corresponding blueprints.105 The flue gases from the ovens were sucked up by an exhaust installation housed in an adjoining room, and blown into the stack at high velocity.106

In March 1943 the three exhaust blowers of crematorium II were seriously damaged and had to be dismantled. As a result, the facilities intended for crematorium III were not installed. Unlike crematorium II, crematorium III was not equipped with the rails via which ovens were loaded; rather, these body conveyances were replaced with litters.107 Such a litter – they were also used in the Topf double-muffle ovens of Mauthausen and in the Kori ovens in other concentration camps – consisted of two parallel metal pipes 3 cm (approx. 1″) in diameter and some 350 cm (11.5′) in length. A slightly concave metal sheet 190 cm (6.2′) long and 38 cm (15″) wide was soldered onto their front, where they were to enter the muffle. The two pipes of the litter were soldered onto the oven door at the same distance apart as the guiding rollers, so that they could glide on them easily. In March 1943 it was decided that this system would also be introduced in crematorium II.108

The operation of the coke-fired three-muffle oven is explained in the corresponding Operation Manual for the Coke-Fired Topf Three-Muffle Cremation Oven,109 which was based on the manual for the double-muffle cremation oven. The only significant difference relates to the heat tolerance of the muffles, which were not to be heated to more than 1000 C (1830F), whereas the double-muffle oven could be heated to 1100 C (2010 F). This lower heat tolerance is due to the lesser quantity of fireproof brickwork per muffle of this oven type (approximately 2,100 kg, or 4,630 lbs) as compared to that of the double-muffle oven (approximately 3,000 kg, or 6,600 lbs), and probably also to the lesser quality of the materials used.

In Germany, cremation in concentration camps had been regulated at the beginning of World War Two by the “decree regarding cremations in the crematorium of concentration camp Sachsenhausen”, which Himmler had issued on February 28, 1940.110 This decree was entirely in accordance with the legal stipulations in effect for civilian crematoria.111 Whether these legal regulations were later modified or rescinded, and/or whether other regulations applied to the concentration camps located in the occupied eastern territories than applied to those in the Reich proper, is not known, but it is certain that the Topf double- and  three-muffle cremation ovens were designed along the same norms as the civilian ovens. The Topf cost estimates for these ovens also list carriages or devices for the introduction of coffins into the muffle, which proves that cremation was intended to include the coffin. This is further established by the operating guidelines, which recommended starting the forced-air blower immediately after the introduction of the body, and to leave it on for about 20 minutes. This recommendation is tailor-made for the circumstance that the bodies enter the oven in coffins, since the rapid and intensive combustion of the coffin requires a large quantity of air. In a cremation without a coffin, on the other hand, this stipulation would be completely pointless, because adding a large quantity of cold air during the beginning stage of cremation, where moisture evaporates from the body – a process which robs the oven of a large amount of heat – would only have slowed the cremation process.

The operating instructions also indicate that the ovens were designed for the cremation of one body at a time per muffle, since they specify that the bodies had to be introduced successively. On July 3, 1940, in order to “put the crematorium into operation”, the firm Topf also offered “500 ash urns” and “500 fireclay markers” to the SS-Neubauleitung of Auschwitz.112 The latter were numbered plates of fireclay, which were placed on the coffin or directly on the corpse to identify the ashes. In 1946, some of these plates were found near the crematorium II. They were handed over to investigating judge Jan Sehn,113 who, as far as I know, never mentioned them in his findings about his investigations on Auschwitz. This confirms that not even in Birkenau corpses were cremated anonymously in masses, but one at a time.

The Coke-Fired Topf Eight-Muffle Cremation Oven

This oven, whose construction was probably shown on the missing diagrams D59555, D60129 and D60132 from the Topf firm, 114 was designed by engineer Prüfer, presumably in late 1941. In any case it was designed along the lines of the three-muffle oven, whose design diagram bears a lower number, namely D59394. On December 4, 1941 the Main Office for Budget and Buildings in Berlin ordered from the Topf firm, “4 double-Topf-4 muffle cremation ovens” for Mogilew in Russia, where POW transit camp 185 was located.115 The order was confirmed on December 9, but only half the oven (four muffles) was shipped to Mogilew on December 30, while the rest remained in Topf’s storehouse for the time being. On August 26, in accordance with the suggestion engineer Prüfer had made on the occasion of his visit to Auschwitz on August 19, 1942, the SS Economic-Administrative Main Office ordered that two of the ovens for Mogilew should instead be sent to Auschwitz. However, the Central Construction Office waited two-and-a-half months before requesting a cost estimate for this model of oven. Topf sent the estimate on November 16. The total price of RM 55,200 – RM 13,800 for each oven – included a 6% surcharge because the company had had to revise the drafts and design new models for the ovens’ fittings so often.115 The blueprints of crematorium IV (and crematorium V, in mirror image) of Birkenau which show the foundations and the vertical cross-section of the “eight-muffle cremation oven”, the photos taken by the Poles in 1945 of the ruins of crematorium V, and the direct examination of these ruins, enable
us to reconstruct this model of oven with sufficient accuracy.116

The coke-fired Topf eight-muffle cremation oven consisted of eight ovens with one muffle each, as shown on Topf’s diagram 58173. Four ovens together make up each of two groups. Each group consists of two pairs of ovens, set up in mirror image so that the back and two central walls of the muffle are shared. The two oven groups are connected by four generators and set up in pairs along the same lines, so that they ultimately form one single oven with eight muffles which is referred to in the corresponding invoice as the “large-area cremation oven”, due to its size (its base covered an area of about 32 m2 , or 344 sq.ft.). The oven was encased in a solid brick structure containing a series of anchor irons. These are clearly visible on the Polish photographs of 1945 and are still present today in the ruins of this crematorium. The heating grates were also designed to burn wood, as one can see from Topf’s invoice of April 5, 1943, where “wood heating” is mentioned. The system for introducing the bodies into the muffles used a litter like that in crematoria II and III; it was affixed on two simplified rollers bolted to the anchor irons underneath the muffle damper. The oven was probably not equipped with forced-air blowers, since none are mentioned on the bill of April 5, 1943. The stacks were designed without exhaust systems. The base unit of the Topf eight muffle cremation oven consisted of two muffles and one generator, and the flue system for the stack gases corresponded to that of the “single-muffle cremation oven” shown on Topf design D58173.

The Cremation Ovens of the Firm of H. Kori, Berlin, and Ignis Hüttenbau, Teplitz

Where the supply of cremation ovens to German concentration camps is concerned, the Berlin manufacturer H. Kori was Topf’s major competitor. Kori’s coke- or oil-fired ovens were installed at Dachau, Mauthausen, Majdanek, Stutthof near Danzig (not to be confused with the Alsatian camp Struthof near Natzweiler), Ravensbrück, Groß-Rosen and Neuengamme, among other places. Strictly speaking, these ovens have no immediate significance to a study of the crematoria at Auschwitz and Birkenau. However, since we shall eventually use some data from Kori ovens to draw certain conclusions about characteristics also present in the Birkenau ovens, we have also analyzed these Kori ovens in detail. Since these analyses would go beyond the scope of the present study, we refer the reader to the relevant sources.117 In the course of 1942, a crematorium was built for the ghetto of Terezín, which was called Theresienstadt at that time. A detailed cost estimate exists for this installation dated April 2, 1942, from the firm Ignis Hüttenbau A.G. of Teplitz-Schönau in the then Protectorate of Boemia and Moravia (today’s Teplice in Czechia).118 Because of the rapid increase of the mortality in the ghetto of Theresienstadt – from 256 deaths in April 1942 over 2,327 in May to 3,941 in June119 –, the crematorium was equipped with four petrol-fired ovens by Ignis-Hüttenbau.120

Coke Consumption of Topf Cremation Ovens of Auschwitz & Birkenau
Heat Balance of Topf Double-Muffle Cremation Ovens at Gusen

The decisive factor influencing the consumption of fuel of a crematorium oven is the frequency of cremation: the higher the frequency, the less fuel is required for each individual cremation. For example, the diagram “Subsequent cremations” published by Prof. P. Schläpfer in 1936 based on practical experiences shows a consumption of over 400 kg of coke for the first cremation, starting with a cold oven, of about 200 kg for the second, and little more than 100 kg for the fourth cremation.121 After the eighth cremation, the graph becomes more or less horizontal, reaching a value of 37.5 kg of coke at the twentieth and last cremation.122 This means that 20 discontinuous cremations separated from each other by a day or more would have required more than (400 × 20 =) 8,000 kg of coke, while 20 consecutive cremations in a warm oven would have required only (37.5 × 20 =) 740 kg. From the tenth consecutive cremation onward the fuel consumption was steady because by then, the refractory material was warmed up and absorbed only as much heat as was necessary to compensate or heat losses due to radiation and convection, i.e., the oven was in a thermal equilibrium. Therefore, in order to find out the minimal fuel consumption of any crematorium oven, it is necessary to establish the conditions when the oven is in a thermal equilibrium, i.e., when the ovens gives off as much heat to the environment as it gets back from the burning fuel.

Between the few relevant surviving documents on the crematorium of Gusen exists a list edited by SS-Unterscharführer Wassner, head of the crematorium of Gusen, which documented the number of inmates cremated and the coke consumption per corpse for the period from September 26 to November 12, 1941. According to this document, 677 corpses were cremated in this crematorium between October 31 and November 12, 1941.123 This amounts to an average of 52 corpses per day, or 26 corpses per day and muffle, with a total consumption of 20,700 kg of coke, or 30.6 kg of coke per corpse. Since these consumption figures are based on practical data, they are a precious point of departure for the calculation of the heat balance of the Topf ovens of Auschwitz-Birkenau. Mathematically, the heat balance of an oven is expressed by an equation consisting of all losses of heat, split up into various factors (heat sinks, for instance loss by radiation, conduction, hot exhaust gases), and all contributions of heat (heat sources, e.g., burning fuel, coffin, corpse).124 Except for the volume of air going through the oven, which depends on the management of the oven, all factors can be calculated. But because in the specific case of Gusen the fuel consumption is known by practical data, all factors can be determined.125

Durability of the Firebrick of the Cremation Ovens

As a result of thermal stresses, the fireproof brick of a cremation oven inevitably wears out, and eventually this becomes a serious hazard. In the civilian cremation ovens which had been constructed in the usual manner and with the building materials normally used in the 1930s, the lifespan of the fireproof brick was about 2,000 cremations, but the Topf firm had managed to extend its durability to 3,000 cremations.183 In the cremation ovens in the concentration camps, the problem of wear and tear on the fireproof brick was greater, not only because of the lesser mass of this fireproof material and its lower quality, but also because of the greater rate of use of the facility, and also due to its operation by untrained personnel whose hostile attitude to their work may very well have been reflected in the carelessness they showed in performing that work. The very real impact of these factors is demonstrated by the case of the Topf double-muffle cremation oven at Gusen. This oven went into service on January 29, 1941 184 but was already damaged only eight months later. On September 24 the SS Construction Office of the concentration camp Mauthausen requested the Topf firm to “immediately dispatch one of your oven specialists to repair the cremation oven in the labor camp Gusen.” 185 Topf sent the fitter August Willing, who arrived in Gusen on October 11 and went to work the next day. From the relevant “receipts for special billing re. day-rate jobs” we know that this work took from October 12 to November 9, 1941. In 68 work hours in the week of October 16 to 22 he replaced the fireproof brick of the oven (“dismantling the oven, and rebuilding inside”). In 52 work hours the following week he finished lining the outside brickwork and performed a test cremation. Willing remained at Gusen until November 9 to tune the oven properly and to supervise its operation.186

From February to October 1941, in a period of 273 days, 3,179 inmates died in the Gusen camp;187 this means that about 1,600 cremations took place in each muffle. This would confirm the average lifespan of the firebrick in a muffle as being about 2,000 cremations. But even assuming that the ovens had been used to the absolute limit of their capacity, the firebrick could not have lasted for more than 3,000 cremations.

Thus, the 46 muffles in the cremation ovens of Birkenau could have cremated a maximum of (46 × 3,000 =) 138,000 bodies. After that, they would have had to be dismantled in order to replace the firebrick. If Pressac were correct in his assumption that these ovens served for the cremation of not only the 100,000 registered inmates who died of natural causes and are proven to have been cremated here, but also for the cremation of an additional 530,000 gassing victims, then the brickwork of the muffles would have had to be replaced (630,000 ÷ 138,000 =) approximately five times. For crematoria II and III alone this would have required 320,000 kg (705,600 lbs) of fireproof material – not to mention the inevitable damage done to the fireproof inner lining of the generators – and if we take the time needed by August Willing in Gusen as guideline, the work would have taken about 9,000 man-hours to complete.

All this would have generated an immense number of documents, yet the extensive correspondence between the Topf firm and the SS Construction Office contains no trace of such paperwork. There are not even any indirect references or other clues that would hint at such a mammoth task – with one single exception: a letter from Topf to the SS Construction Office, dated December 9, 1941, which indicates that the Construction Office had ordered “one wagonload of firebrick” from Topf. This material, which was enough “for the new construction of one oven”, was to be used “as replacement material for repair work.” 188 Taking into consideration this restoration of the fireproof brick of two muffles, the six muffles of the Auschwitz I (the Main Camp) were able to cremate a total of 24,000 bodies. From all this it follows that the ovens of Auschwitz I and Birkenau (Auschwitz II) altogether were able to cremate about (138,000 + 24,000 =) 162,000 bodies during the period of their existence. This figure agrees quite well with the number of known, deceased registered inmates. Thus, the cremation of the supposed gassing victims was physically impossible in technological respects as well.

One thought on “The Crematoria Ovens of Auschwitz and Birkenau

  1. Good on you Adam for NOT censoring important hidden truths. For refusing to bow down to the (((rotten plague of humanity))). A good book to read The Myth of German Villainy by Benton L. Bradberry UK book depository

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