From the Holocaust Site
Some Jews were deliberately kept alive to assist with the killing process. Formed into Sonderkommandos, or special detachments, they were the ones who told the new arrivals to undress and then led them to the “shower room.”
One of the few members of the Sonderkommandos who survived Auschwitz described the killing site:
"It was surrounded with a fence of sorts, made from piles of logs, two meters high, so you wouldn’t notice a thing from the outside. Around the crematorium was an electric fence. There was an entrance that led to a large yard. The yard was about twenty meters long and it led to the building where the furnaces were. We led the victims to the left side, where there were stairs, and then down to the undressing hall. Over the undressing hall [and gas chamber] there was no other floor. There were just four openings through which the SS men threw in the gas in order to kill the people. To keep air from coming in, they would close the lids above the openings. . . . "
Because the Germans needed the Sonderkommandos to remain physically able, they were granted much less squalid living conditions than other inmates: they slept in their own barracks and were allowed to keep and use various goods such as food, medicines and cigarettes brought into camp by those who were sent to the gas chambers.
Unlike ordinary inmates, they were not normally subject to arbitrary, random killing by guards. Their livelihood and utility was determined by how efficiently they could keep the Nazi death factory running.
Every few months, the Sonderkommandos were themselves murdered and replaced by a new group of prisoners.
May God forgive us our sins. As a Species, we leave a lot to be desired.