Before entering service in Sobibor, Floss was stationed in Buchenwald and several euthanasia centres.

In the early period of Sobibor, Floss was the acting commander for a few weeks until he was succeeded by Gustav Wagner.

According to Erich Fuchs, Floss participated in the trial gassing of several dozen Jewish women at Sobibor.

[2] Fellow Treblinka SS officer Heinrich Matthes described this period: "Floss arrived at this time [November 1942], who, so I presume, must previously have been in another camp.

"[3][4] By the end of July 1943, the Jewish "death brigade" in Camp II, supervised by Floss, had cremated about 700,000 corpses.