Before and during World War II, all departments of Linde AG were in some way involved in the armaments production: The Heylandt-Gesellschaft für Apparatebau supplied the German rocket program, other branches produced welding equipment and engines for the armaments industry. In 1941, Linde manufactured oxygen and helium installations for IG Farben at the Auschwitz concentration camp. Three further planned installations were not installed due to the course of war. According to estimates of the company for mid-1944, between 400 and 500 people were used as forced labourers in production plants. Although the number may be overstated, the company claimed that 75% of its production facilities were destroyed during the war.