http://www.jewishgen.org/ForgottenCamps/Camps/chelmnoeng.html
Chelmno was established December 1941. The first commandant was Herbert Lange.It operated three gas vans using carbon monoxide. The camp began operations on December 7th, 1941 and ended operations on March 1943. The estimated number of deaths is 150-300,000, mainly Jews.
Chelmno, also known as Kulmhof, was a small town roughly 50 miles from the city of Lodz. It was here that the first mass killings of Jews by gas took place as part of the 'Final Solution'.
By these means, about 145,000 people were murdered at Chelmno in the first phase of its operations. From December 7th, 1941 to September 12th, 1942 15,200 Jewish slave laborers from the Lodz region were gassed at Chelmno.
Amongst the deportees were Jews from Germany, Austria and Czechoslovakia who had been transported to the Lodz ghetto. After the assassination of Reinhard Heydrich and the annihilation of the Czech town of Lidice, 88 children from there were sent to Chelmno and murdered.

On January 17th, 1945 the work group, numbering 48 men, was to be shot, but the Jews revolted and in the ensuing melee a handful escaped. http://www.ushmm.org/wlc/en/article.php?moduleld=10005194 Under German occupation in World War II, Chelmno was located in the Wartheland administrative unit (seat Poznan/Posen). SS and police authorities established the Chelmno killing center in order to annihilate the Jewish population of the Wartheland, including the inhabitants of the Lodz ghetto.
The “killing center” consisted of an unused manorial estate in the town of Chelmno itself and a large forest clearing approximately 2.5 miles northwest of Chelmno off the east side of the road to Kolo and abutting the village of Rzuchow to the south.
The SS and police began killing operations at Chelmno on December 8, 1941.
Seven Jews are known to have escaped from Chelmno; all worked in the burial detachment. Mordechai Podchlebnik, Milnak Meyer, Abraham Tauber, Abram Roj, and a mysterious "Szlamek," whose actual identity has never been fully established, escaped during the winter of 1942; Mordechai Zurawski and Simon Srebnik escaped from the labor detail dismantling the killing center in January 1945. Podchebnik, Zurawski, Srebnik, and Roj survived the war. Though he did not survive, "Szlamek" found refuge in the Warsaw ghetto and told of his experiences. The Jewish underground movement smuggled Szlamek's account that the Germans were systematically killing. http://www.britannica.com/EBchecked/topic/108480/Chelmno AuschwitzEuropeBelzecWarsawSilesiaPrussiaVistula RiverCarpathian Mountains
Chelmno, Polish Chełmno, German Kulmhof, Nazi German extermination camp on the Ner River, a tributary of the Warta, in German-occupied western Poland. It opened in December 1941 and closed in January 1945 and was operated to execute Jews, most of whom were Polish.
Its victims were from the Łódź ghetto and from 36 communities in western Poland. Also sent to Chelmno were 88 children from the Czech town of Lidice, whose population