I came across this thread: https://www.reddit.com/r/AskHistorians/comments/5ycd9h/if_a_nazi_soldier_was_crippled_in_some_way_during/
Which linked to this article: https://www.ushmm.org/wlc/en/article.php?ModuleId=10007064
That article cited the following:
"From January 1940 to August 1941, more than 70,000 men and women were transported to one of six specially staffed facilities in Germany and Austria and killed by carbon monoxide poisoning in gas chambers disguised as showers."
Having read a lot about gas chamber executions in the US and how awful and painful they are unless the victim purposefully succumbs to the fumes and essentially tries to breathe enough in to pass out, why was carbon monoxide not continued by the Reich?
In other words, if the purpose was extermination - fine - horrible, but that's the history - but why utilize such a contaminating substance to painfully exterminate people when it's my understanding carbon monoxide poisoning is odorless, ostensibly silent, and just puts people to sleep rather painlessly and perhaps without the fear (at least the fear that's depicted in every holocaust movie I've ever watched).
The main reason for the switch was the greater efficiency of Zyklon-B over carbon monoxide. The SS's experience with carbon monoxide for the T-4 euthanasia program made it the initial go-to method for Operation Reinhard, so naturally the original facilities used this gas as a main killing method. T-4 not only created a supply infrastructure, but also experience among people like Kurt Gerstein with sundry issues like the ideal amount of gas to use to kill large numbers. Gassing by carbon monoxide had a several problems when extended on a mass scale and the SS was looking for alternative killing methods by the latter half of 1942.
It was not so much the lethality of carbon monoxide that concerned the Germans, but the delivery system. Carbon monoxide poisoning either required bottles of the gas or an engine on site. The scale of Operation Reinhard often overwhelmed the capacity of the existing camps' gassing facilities to supply the requisite gas. The engines needed maintenance after constant operations and could breakdown, causing delays in the killing operations. Moreover, they were noisy and this noise undercut the deception that allowed for more orderly executions. Zyklon-B was much more attractive in this context. Although it was a pollutant, this was less of an issue once the inmates had shaved their hair and shed their clothes. The canisters of cyanide gas were also portable and easily storable, much more so than compressed air cylinders. The gas also resolved the headache of having to keep the diesel engines running and skilled technicians to run them. A high tempo for killing operations was made much easier by the switch. When Claude Lanzman interviewed Treblinka guard Franz Suchomel for Shoah, Suchomel noted that Treblinka's extermination apparatus was a "well-functioning assembly line of death," using mainly carbon monoxide, but Auschwitz, which used Zyklon-B, was a true factory.
This is only tangentially related, but how much were the Einsatzgruppen's procedures for killing discussed in the planning of Operation Reinhard? Overviews of the latter always say that its methods were adapted from those of Action T4, but I continue to wonder about the likelihood that the leadership of Reinhard knew about the Einsatzgruppen's unprecedented rates of killing and felt any pressure to emulate them in some respects, even though their tools were different.