Their was 4 big ones and 1 little barracks in Chelmno.
Chelmno and Belzec came into operation as an extermination camp a few months before Auschwitz II.
About 152,000 people were killed at the Chelmno extermination camp, however it is estimated that the total death toll, taking into account starvation, disease, etc, is 300,000. The Chelmno camp was also used for early experimentation and for trialling mass murder methods
Sonderkommandos were at the death camps: Auschwitz, Birkenau, Sobibor, Treblinka, Belzec, and Chelmno. Though every camp needed burial and corpse disposal squads (as there were many deaths from starvation/disease, exhaustion/beating and euthenasia).
5,000 gypsies died at Chelmno.
I don't know how many but I know that at least 153,000 people were killed in Chelmno.___Chelmno the first Nazi extermination camp ('killing facility') and the aim was to kill the new arrivals within 24-48 hours of arrival. It did not have a permament population of prisoners, apart from a small group that had to dig graves in a nearby forest and bury the dead. It was not a camp in any conventional sense. The estimated death toll was - as stated above - 153,000 and the were only two (!) known survivors. One of these was a 'pipel'.
Practically none starved. Chlemno was the first Nazi extermination camp and the aim was to gas all new arrivals as soon as practical - usually within 24 hours.
There were six extermination (or 'death') camps in the Holocaust which were located at: Auschwitz-Birkenau, Belzec, Chelmno, Majdanek, Sobibor, Treblinka. That is the 'accepted list', but the role of Majdanek is not clear and there was also an extermination camp at Maly Trostinets near Minsk.
The extermination camp operated from December 1941 till March 1943. It reopened briefly in June 1944 for two months. News of the camp reached London (via the Polish Resistance) late in December 1941.
By 1941, the Nazis began building Chelmno, the first extermination camp (also called death camp), in order to "exterminate" both Jews and Gypsies. In 1942, three more death camps were built (Treblinka, Sobibor, and Belzec) and used solely for mass murder. Around this time, killing centers were also added at the concentration camps of Auschwitz and Majdanek. So i would say 6 or more.
Built by Nazis to carry out the mass extermination of Jews through gas chambers along with other brutal methods; included Chelmno and Auschwitz; many would have crematoriums built to hide the evidence of this mass murder
It is said around 152,000 people perished in Chelmno. There have been only 2 known survivors.
The number of prisoners placed in each Barrack varied by camp, so there isn't an exact answer but it was usually a few hundred.