45. Can a crematory oven be operated 100 % of the time?

Ernst Zündel Replies:
Rebuttal # 45

A bit of background information first.

Cremation of the dead is not a new concept. It has been practiced by many cultures for many centuries. In Europe it is a relatively recent practice, since it was frowned upon by the Catholic Church, which relaxed its opposition only in the late 18th century.

There are many practical reasons for the use of creation. Cremation allows a more effective control of infectious diseases. It does not take up the much-needed land for ever expanding graveyards, which is very important in overcrowded areas. It also eliminates the need to store corpses in the winter when the ground is frozen. There is nothing sinister about cremation per se.

Europe’s early crematories were coal- or coke-fired furnaces. The oven or furnace which is used to cremate corpses is properly termed a retort.

Early retorts were simply baking kilns which cooked all the moisture out of the corpse. Modern retorts actually blow fire from a nozzle into the remains, causing combustion. Modern retorts also have an extended combustion chamber (afterburner) with a set of baffles to introduce turbulence into the fuel gases and to facilitate the complete burning of particles that did not burn in the main chamber.

The modern furnaces operate at a temperature of 1100 C (2000 F) or just above, with the temperature falling along the length of the afterburner. Bones cannot be burned and must be crushed by mechanical means, which nowadays is done by putting them in a high-speed rotating drum containing steel balls. In the old days it was done with a mortar and pestle.

Modern retorts are mostly gas fired, even though there are still some using oil. There are no more coke- or coal-fired crematoria in the US or Canada.

During the second Zündel Trial in 1998 in Toronto, the court heard testimony of Ivan Lagace, who was at that time crematory manager at the Bow Valley Crematorium in Calgary, Alberta. He was recognized by the court as an expert in the practical aspects of crematorium practices.

Mr. Lagace testified that an average time to cremate a human body in a modern gas-fired furnace at the temperature of just over 1000 degrees C (about 2000 F) is two hours. Smaller bodies could be cremated in about 1.5 hours. The time of 1.5 hours was given in a Toronto Star article for 17 September 1996; the article mentioned a temperature of 1000 C, which can only be achieved in modern gas or oil-fired crematory furnaces with a direct application of flames to the corpse.

Heat energy required to cremate a corpse, according to that same Star article, ranges from 800,000 to 1.2 million BTU. As mentioned above, older furnaces were fired by coal or coke. Coke produces very short flames which means there is no flame contact with the corpse in those furnaces.

This mode of operation produces an average temperature of about 800 C (1470 F) in the immediate vicinity of the corpse, which extends cremation time to 3.5 to 4 hours for each corpse. The coal and coke furnaces do not burn uniformly and combustion has to be continuously monitored, with the operator adding more coal, if necessary, poking it, and controlling the introduction of air by dampers.

The crematories utilized in German camps were of the older type. All of the ovens had multiple retorts and all were coke fired. None of the retorts in German camps were designed for multiple corpse incineration, as claimed in exterminationist literature.

In view of all this, one can see how preposterous is the claim that it took a half-hour to 45 minutes to incinerate a corpse in a WWII type German crematoria. But still, it is a considerable “progress” from 5 (five) to 9 (nine) minutes, that it took to incinerate a body according to the report by the Soviet State Commission, which investigated Auschwitz in 1945.

Can a crematory oven be operated nonstop – “nonstop” meaning that you start the next cremation immediately after completing the previous one?

Factory recommendations for normal operation and sustained use of crematoria furnaces allow for three or less cremations per day. Any attempt to exceed that would put a great stress on refractory specialty brick lining, which will result in a faster wear and the need for replacement.

The crematory furnace consist of a shell, constructed of a hard brick, which is lined with a refractory brick from the inside. The main quality of the refractory bricks is their ability to withstand high temperature. Another important quality is their low heat conductivity, which helps to protect the structural bricks of the crema wall from excessive heat for which they are not designed.

A brick of refractory lining is very soft and fragile. You can easily scratch it with your fingernail, which also means it can be easily damaged – for example, with a poking iron.

According to Ivan Lagace, an average life expectancy of refractory bricks is about 1500 cremations. Refractory bricks can also be severely damaged when a corpse is introduced into a hot furnace that was not allowed to cool down fully following a previous cremation. This happens because water in body tissues is instantly brought to boiling temperature and the tissues quite literally explode, splattering body fluids and wet tissues all around.

One can imagine what will happen to a red-hot brick if you splatter water on it! There will be plenty of spalling and flaking; it may even crack! That is why it is very important to either allow a cooling-down period after a cremation or to reduce the rate of combustion by the end of cremation, thus allowing the temperature to gradually come down.

Either of these options, obviously, reduce the number of cremations that can be performed in a day. And let’s not forget that in order to cool down a gas-fired furnace you simply shut off the flow of gas, but it is much more cumbersome with coal, since even after no more coal is fed to the furnace, it will take some time for the coal still in the furnace to burn up.

We also have to keep in mind that coke slag had to be removed from the furnaces, possibly more than once a day. The ash which was settling in the flue ducts and chimneys also had to be removed manually on a regular basis. Those are very labor-intensive operations. The Holocaust writers keep insisting that cremations were being done “around the clock”, “nonstop”, “with hundred per cent duty cycle”; that the crematory ovens were operating “100% of the time”; and so on, claiming the numbers of bodies that were being incinerated daily in each oven in the hundreds. That is nonsense for technical reasons.

Here is an excerpt from the operating instructions for the crematory operators of an American-manufactured crematory. For the sake of brevity we skip some paragraphs, leaving only those which reveal the duration of various operations involved in the cremation process, as well as those items which indicate a possibility of excessive wear of the furnace components. The copied paragraphs retain the exact wording of the manual. For that reason, conversions to degrees C are not provided. In order to do that simply divide Farenheit by 1.8, subtracting 32 at those levels will not improve accuracy.

(note to paragr. 3) A. “Your Retort has a timer which has to be set for length of time to be allotted for entire cycle of Cremation. Rotate center knob on the timer counterclockwise until indicator pointer is set at two (2) hours and thirty (30) minutes. […]

5. Upon the start of the blower, the timer has now began to run towards completing the two (2) hours and thirty (30) minute cycle.

[…] 7. Now close the door by pressing the door “Down” button. You are now starting your Preheat Cycle. This will take twenty (20) minutes.

NOTE: This time of PREHEAT for the after compartment is important to prevent any smoke and odor coming out of the hot air duct. […]

After the Preheat Cycle has been completed, open the door. Now place a wooden roller approximately 1.5″ to 2″ in diameter by 12 to 14 inches long on the floor center tile 18 inches in from the front of the Retort.


Use of any metal type roller will cause excessive wear on the floor tile and shorten the life period of the floor tile. […]

12. (after positioning the casket) Now start the main burner by pressing the main burner “Start” button. The Cremation will take approximately two (2) hours to be completed.

A. It should be noted that the “Fuel Saver Device” will begin operation at that point in time when the temperature reaches 1450 F. The main burner will automatically be positioned to the low-fire position and remain there until temperature drops below the 1600 F level.

13. At the end of the two (2) hour cremation cycle, the timer will automatically turn-off the Retort.

14. Open the door upon completion of the two (2) hour time to check cremains (sic). If the case is complete, close the door. Now start the blower and leave it run for a minimum of (1) One Hour. (one (1) hour 15 min. preferred) to cool the retort down on the cooling cycle. However, if the case is not complete, close the door.

Now initiate steps 5,6 and 12.

Allow cremation cycle to continue until case is complete. […] Always check the cremains (sic) before continuing.

15. The cooling cycle is now completed. Now check the ash tray for any residual fluids etc., that might not have been consumed during the Cremation Cycle.


The ash tray is “HOT”. Asbestos gloves should be used to pull out the ash tray. Serious injury (burns) could happen to the operator’s hands by failure to use the proper equipment. […]

16. Turn off the blower.

17. Open the door.

18. Brush the cremains into the ash pit hole. […]


Radiant heat will be coming out the door. Asbestos gloves should be worn to prevent injury (burns) to the hands when using the brushes.

19. Close the door.


Always close the door when the Retort is hot, and when it is not necessary to have it open to perform a function.

20. Remove the ash tray from the ash pit. Place the second ash tray in the ash pit.

21. When doing more than one case per day, the cooling cycle must be (1) One Hour… (one hour 15 min preferred) between the first and second case minimum. The cooling cycle time between the second and third case of the day must be two (2) hours… (two (2) 15 min preferred).

A. When running more than one case in the same day with not more than the cooling cycle described above being used. “The Preheat Cycle is five (5) minutes approximately or 800 F on temperature indicator between the first and the second case or second and third case of the same day.

22. Your Retort is designed and constructed in such a manner that a “BREAK-IN PERIOD” is required. The “BREAK-IN CYCLE” is one case per day for the first twenty-five (25) cases to be processed. At the completion of the “BREAK-IN CYCLE”, your Crematory Retort has been cured out. (refractory is dried out).


Failure to conform to the “BREAK-IN CYCLE” will void the Warranty! It could cause damage to your retort, requiring repairs that would be the responsibility of the owner for the costs.

23. Factory recommendations for normal operation to your Crematory Retort is a maximum of three (3) cases per day in a normal eight (8) hour work day. No more than 50-60 cases should be processed in any month so that the refractory life is prolonged.

24. When processing more than one case per day, the above procedures will be followed for the first case, with particular attention paid to paragraph 21.


Failure to follow procedures outlined in paragraph 21 could result in improper combustion.

25. Should time lapse of more than four (4) hours occur between the first case and the second case, the Preheat Cycle of fifteen (15) minutes must be performed prior to the starting of the second case.


Failure to perform the Preheat Cycle could result in odor and smoke coming out the hot air duct. […]

(The note to par. 12 is not a misprint. It simply means that the temperature will still be going up even in the Fuel Saver mode, only it will be rising at a slower rate. For an efficient control you have to introduce hysteresis, which means that the different control modes are turned on or off not simply upon reaching a certain threshold, but depending on a direction of the parameter change through a threshold. In other words, it will turn into a low-fire mode at 1450 F when the temperature is rising, but it will go back to normal mode at 1600 F when temperature was going down through that threshold. This is done to prevent the controller from changing the mode of operation several times a minute.)

From that manual for the crematorium furnace operation we can begin to appreciate the technical difficulties associated with cremation! You simply cannot exceed the capacity of the furnace if you plan to keep it in a good working order. Repairs of this kind of equipment are very labor-intensive and take a long time to properly accomplish. Just imagine what it means to replace the refractory lining!

You would have to cool the furnace down to the temperature which would allow people to work inside. According to Ivan Lagace, cooling would take a minimum of 48 hours. Replacing the lining is a very involved operation. The entire surface of the furnace has to be covered with those fire-resistant bricks; you cannot leave even a tiny spot of the oven structure without protection from the furnace heat!

The manual also mentions a break-in cycle for the newly built furnace. According to the testimony of Ivan Lagace, you have to go through the same procedure after every repair of the refractory.

This involves running the oven at a very low combustion rate for a while. Only then can you resume cremations, according to Lagace. For the next 25 days, you can only perform one cremation a day, exactly what we saw in those excerpts from the manual. And no matter whether a whole lining had to be replaced or just a few bricks, you still have to shut down the furnace, let it cool down to the temperature that would allow people to work inside and then go through the entire break-in process.

Considering all this, it is inconceivable that the Germans would be trying to perform more cremations than the ovens could realistically withstand. As mentioned by Lagace, there is always some flaking of the lining, even during normal operation. The brick may even crack if overheated, and the crack may be very large, to the entire depth of the brick. In that case the fire would not be contained within the retort and the exterior structure would be exposed to temperatures exceeding those it can safely withstand. That would cause a serious emergency which could lead to the collapse of the entire furnace structure if not promptly discovered and corrected.

That is why it is very important to perform regular inspections of furnaces. In order to inspect the lining, an engineer had to crawl inside the furnace and closely examine every brick. It may take two days for the furnace to get cool enough to allow people to work inside. Failure to perform inspections would entail a considerable risk of severe damage to the oven structure, which would result in an even greater down time.

It must also be stressed that the number of 1500 cremations per life of a refractory lining, given by Ivan Lagace, refers to an average time, which means that one lining could have survived 1700 cremations, while the other had to be replaced after 1300. Considering the fact that, with the exception of two furnaces in Majdanek I, which had one retort each, all other furnaces had multiple retorts, which means several furnaces on the same foundation and with the flue channels merging into the same smoke stack.

Auschwitz-Birkenau had furnaces with 2 retorts, 3 retorts and even 4 retorts each, adjacent retorts sharing a wall. This means that the entire group of retorts had to be shut down in order to make repairs in just one retort. So if the lining in one retort had to be replaced, say, after a “mere” 1300 cremations, what should be done next? Do we then restart the furnace, while there is only 200 cremations left in the average capacity of the other retort(s)? Or would it make more sense to strip the old lining from the other one, two or three retorts, whatever the case might be, and put a new one in? One option would take more time and effort for repair, while the other would allow to avoid an extra period of reduced capacity due to break-in period.

Multiple-retort furnaces are more economical from the purely thermal point of view. They allow a considerable reduction in coke consumption. For example, a three-retort furnace required only 20 kg of coke for the cremation of each emaciated adult corpse. However, their maintenance and repair involve a greater loss in cremation capacity during a down time. That could be another reason why the Germans provided such a considerable reserve cremation capacity in Auschwitz-Birkenau.

Even if we imagine that, during the typhus epidemics in the camps, the furnaces had to be operated “around the clock”, it is inconceivable that the Germans would be operating the ovens in excess of their capacity, thus causing so much “wear and tear” on the refractory lining that it would require more frequent repairs than could be achieved under proper operating conditions.

Fred Leuchter, in his report (which is available from Samisdat 206 Carlton Street, Toronto, Ontario, M5A 2L1 CANADA, as is the testimony of Ivan Lagace), gives a set of numbers with regards to cremations that were realistically possible in German camps. He puts an average theoretical capacity of 6.8 corpses per retort per 24-hour period, while the realistic, practical capacity is even lower, just 3 (three) corpses in 24-hours. This gives a “theoretical average” for Auschwitz-Birkenau of just over 350 corpses a day, while the realistic value, given by Leuchter, is 156.

In light of these numbers, and the above technology involved, you can appreciate how absurd are the numbers thrown around by Holocaust propagandists, according to which thousands of bodies were being incinerated each day in Auschwitz-Birkenau crematoria. It is important to emphasize that even these numbers are too high, since they do not take into account the down time due to inspections, maintenance, repair and periods of drastically reduced cremation capacity during the break-in periods following repairs. It also does not take into account the fact that after the completion of Krema installations at Birkenau, those at Auschwitz were no longer used and the Krema I building was converted into a bomb shelter.

There is no room to go into those details here, but Samisdat has books in its catalog which extensively describe such things, for example, a report by Germar Rudolf who conducted forensic examination of several camps soon after Leuchter.

The same can be said about the claims that the Germans were supposedly putting three bodies at a time in each retort. It should be obvious to anybody that in a properly designed crematory oven the combustion chamber should be big enough to allow adequate circulation of flames and flue gases around the body. However, making the chamber too large would, obviously, mean that plenty of flue gases would escape through the smokestack without giving away their energy to the corpse, which, of course, is wasteful.

On the other hand, a chamber that is too small would not allow adequate volumes of hot flue gases to pass by and circulate around the body, thus slowing down the cremation process. It might simply be impossible to maintain a combustion process of adequate volume and intensity, since an obstructed combustion chamber would plug the escape route for flue gases.

It is, of course, possible to design a furnace that would be able to burn three or even ten bodies at a time, but the German crematoria were not of that type, as is manifestly obvious from examination of either existing furnaces that are being shown to tourists in the camps or from the old engineering blueprints.

In summary:

According to the Holocaust propagandists, the mere presence of crematoria in the camps means the proof of the program of mass extermination. But these days, not even the hard-core exterminationists claim that Buchenwald or Dachau were extermination camps, and yet each of those had a crematory.

The exterminationists like to point at the total number of 52 retorts at Auschwitz-Birkenau and claim that as a proof of the extermination program. It is a known fact that after completion of crematoria in Birkenau, Krema I in Auschwitz was no longer used and was later converted into a bomb shelter. So we only need to consider 46 retorts at Birkenau. And if we look at the death statistics in Auschwitz, we can appreciate the rationale for this considerable reserve capacity.

During the first 20 days of August 1942, in the male sector alone, there were 4,113 deaths – an average of 216 deaths per day. During the remaining part of that year more than 20 thousand inmates died of typhus. Taking this into consideration, it is reasonable to assume that the Auschwitz administration would have ordered the construction of 46 retorts on the basis of the projected worst case.

By comparison, in 1939 some 102 thousand people died in Germany, with an average of 280 per day. At that time there were 131 crematoriums with approximately 200 ovens. We can see that on average there were 1.4 cremations per oven per day.

This considerable reserve capacity existed in Germany even in peace time and even considering the fact that most people were dying of causes other than infectious diseases, mostly old age. But in camps during the war the main cause of death was typhus, so it was very important to dispose of those bodies as fast as possible, which explains this reason for that reserve capacity.

Between the period of December ’41 to March ’43 there were six operational retorts at Auschwitz. If we assume 6.8 theoretical cremations a day, then during that period of time there could be approximately 6.8×480=3264 cremations. The more realistic number of three bodies per retort per day would come up to 3×480=1440. Again, this is disregarding the down time and the periods of reduced capacity.

In March 1943 Birkenau Krema II was completed, but after a short period of service it had to be shut down and the refractory lining redone. Krema IV, containing two furnaces, four retorts each, was completed at the end of March. It operated for just two months and was abandoned in May ’43. In April Krema V, containing two furnaces, four retorts each, was finished. Therefore, in April ’43 sixteen more retorts were operational for a total of 22. This number of operational retorts stayed the same for the next six weeks. Krema III started operating on 25 June ’43, after which Krema I was shut down. On 12 July the rework on Krema II was completed. Krema V was mothballed at about the same time.

We will not bore the reader with calculations of the “theoretical” and realistic cremation capacities. Those who are interested can work it out with a calculator. All we want to show here is that ovens were often being repaired, and the claims of the holocaust writers to some smooth, trouble-free operation every single day, around the clock, twelve months a year, for years in a row, is simply preposterous.

It is now claimed today that 1.5 million people perished in Auschwitz. Originally it was claimed that 4 million were killed. There was even a commemorative plaque, claiming 4 million. In 1989, under the pressure of evidence, to which the revelations of the Zündel Trials contributed a great deal, that plaque was removed, and after that, the most often quoted number moved into the range of 750 to 850 thousand.

Then it was raised again!

Somehow the “conductors” of this show do not see anything wrong with all these manipulations with millions. But the most “suspicious” flaw in their “arithmetic” is the simple fact that if six million was the alleged total of the Jewish dead, with four million originally “allocated” to Auschwitz. How is it conceivably possible, then, to hold on to those six million in the light of the fact that the Auschwitz total was eventually considerably reduced – by more than three million, according to some exterminationists?!

As mentioned in QA # 1, the “death books” of Auschwitz – more than forty volumes! – have been released in 1989 by Mr. Gorbachev. Out of 74 thousand entries, only about 30 percent have names that could be attributed to Jews!

One final, specific point. Nizkor claims that “…more recently, the Holocaust-deniers have begun to rely on the testimony of Ivan Lagace, who apparently said at the Zundel trial and later in print that it takes six to eight hours per body.”

This is a lie. The average time, required for cremation of a body in a modern, gas-fired furnace, even according to Lagace is 2 (two) hours, with larger bodies taking as long as 2.5 hours. Lagace specifically said that the fat bodies are easier to burn, but the lean ones are very “stubborn fuel”, because they have a greater percentage of “wet tissues”.

Samisdat has an entire set of trial transcripts and also a book that includes all witness testimonies of the second Zundel trial, including that of Lagace. The entire Lagace testimony can be found at http://www.webcom.com/ezundel/english/dsmrd/dsmrd26lagace.html

Anybody interested in this subject but without the patience for detail may consult any good Encyclopaedia or the local crematory in their area. They will be shocked to discover how they have been lied to by the Holocaust propagandists all along.

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