Chełmno extermination camp, also known as the Kulmhof concentration camp, was a Nazi German situated 70 km from Łódź, Poland.  The camp opened in 1941 with the purpose of killing the Jews of the Łódź Ghetto.  At least 153,000 people were killed in the camp. The death camp operated from December 8, 1941 until April 1943 when it was closed down and blown up. A special SS troop gassed people with exhaust fumes and then burnt them. It operated three gas vans using carbon monoxide.

The SS and police transported the victims by truck from the places in which they lived to the grounds of the manor house in Chełmno. Guarded by SS police, the victims disembarked one truck at a time in the courtyard of the manor house. SS officials, often wearing white coats to induce the impression that they were physicians, explained to the deportees that they would go to Germany as laborers, but first had to bathe and have their clothes disinfected. Occasionally they would be greeted by a German officer dressed as a local squire with a feather cap. He would thank them for coming and say some would be staying to work there.

The Jews then entered the manor house. Once inside they were led to a heated first floor room where they undressed and handed over their valuables against receipts to a Polish civilian, who was employed by the special detachment. SS and police personnel led the naked prisoners to the cellar, where they had to walk down a ramp sloping into the back of a large paneled truck that could hold 50-70 people. When the back of the van was full, the doors were closed and sealed. The mechanic on duty attached a tube to the van’s exhaust pipe and then started the engine, pumping carbon monoxide gas into the space where the prisoners were crowded, killing them by asphyxiation. After the victims were dead, the tube was detached from the exhaust pipe, and the van, now full of corpses, was driven to the forest camp, where the bodies were transferred into previously excavated mass graves. Any victims found to be still alive as the corpses were being unloaded were shot by SS and police officials on duty at the forest camp. 

A few Jewish prisoners were selected from incoming transports to form Sonderkommando (special unit) of 50 to 60 men deployed at the forest camp. They were forced to remove corpses from the gas vans and bury them in the mass graves. Because the graves quickly filled and the smell of decomposing bodies began to permeate the surrounding area, including nearby villages, the SS and police ordered in the spring of 1942 that the bodies be burned on open air "ovens" made of concrete with pipes used for air ducts and long ash pans in the forest camp. Jewish Sonderkommando members were also responsible for exhuming the graves and burning the previously interred bodies. In addition, they sorted the clothing of the victims and cleaned the vans. Another small detachment of about 15 Jews worked at the manor house, sorting and packing the belongings of the victims. Periodically, SS and police officials would kill the members of the Jewish special detachments and replace them with laborers selected from more recent transports.

Beginning in September 1944, a group of Jewish prisoners was forced to exhume and cremate any remaining corpses from the mass graves at Chełmno to obliterate any other evidence of mass murder operations. The SS and police shot about half of the 80-man detachment after this work was done in November 1944. The Germans abandoned the Chełmno killing center on January 17, 1945, as the Soviet army approached. 

Trials for the crimes committed at Chelmno took place from 1947 to 1950 in Poland and from 1962 to 1965 in West Germany.  In the first two trials, two staff members of the camp, Walter Piller and Hermann Gielow, were sentenced to death.  In the Second trial, three camp staff members were sentenced to thirteen years and one to seven years in prison.