Beginning in 1926, Ambros worked at BASF in Ludwigshafen. In 1930 he spent a year studying in The Far East. From 1934 he worked at IG Farben, becoming head of their Schkopau plant in 1935. His division of IG Farben developed chemical weapons, including the nerve agents sarin and soman. In this capacity, he was an advisor to Carl Krauch, a company executive. The name sarin is an acronym of the initials of the discoverers, with Ambros being the "a". Ambros then managed the IG Farben factories at Dyhernfurth, which produced tabun , and at Gendorf, which produced mustard gas. The Dyhernfurth factory included a slave labor concentration camp with about 3000 prisoners who were used for the most hard and dangerous work at the plant, and as human guinea pigs in nerve gas experiments. At IG Farben, Ambros also helped research how to produce polybutadiene rubber, which they gave the trade name "Buna rubber" because it is made using butadiene and sodium. This was an important project because the war cut off Germany from raw materials for natural rubber, and in June 1944 Ambros was awarded a prize of one million marks by Adolf Hitler in recognition of this work. In 1941 Ambros selected the site for the Monowitz concentration camp and the Buna Werke factory, which produced Buna rubber using slave labor from the Auschwitz camp, and he then spent the rest of the war serving as plant manager of Buna-Werk IV and managing director of the synthetic fuel production facility at IG Auschwitz. In 1944 Ambros was awarded the Knight's Cross of War Merit Cross.
Ambros was arrested by the US Army in 1946. He had overseen the IG Buna Werke rubber plant at Monowitz in the Auschwitz complex. At the IG Farben trial in Nuremberg in 1948 he was sentenced to eight years' confinement, and was ultimately released from Landsberg Prison early in 1951. The extensive works were to have produced Buna rubber, or polybutadiene for use in rubber tyres. Monowitz was built as an Arbeitslager ; it also contained an "Arbeitsausbildungslager" for non-Jewish prisoners perceived not up to par with German work standards. It held approximately 12,000 prisoners, the great majority of whom were Jewish, in addition to non-Jewish criminals and political prisoners. Prisoners from Monowitz were leased out by the SS to IG Farben to labor at the Buna Werke, a collection of chemical factories including those used to manufacture Buna and synthetic oil. The SS charged IG Farben three Reichsmarks per day for unskilled workers, four per hour for skilled workers, and one and one-half for children. By 1942 the new labour camp complex for IG Farben prisoners occupied about half of its projected area, the expansion was for the most part finished in the summer of 1943. The last 4 barracks were built a year later. The labour camp's population grew from 3,500 in December 1942 to over 6,000 by the first half of 1943. By July 1944the prisoner population was over 11,000, most of whom were Jews. Despite the growing death-rate from slave labour, starvation, executions or other forms of murder, the demand for labour was growing, and more prisoners were brought in. Because the factory management insisted on removing sick and exhausted prisoners from Monowitz, people incapable of continuing their work were murdered at the death camp at Birkenau nearby. The company argued that they had not spent large amounts of money building barracks for prisoners unfit to work. The Buna camp was described in the writings of Primo Levi, the Italian Jewish chemist and Auschwitz survivor.
