They developed out of the situation. The courts brought in a lot of people who had to be shot. I always objected to having to use the same men for firing squadrons over and over again. During that period one day my camp leader, Karl Fritzsch, came to me and asked me whether I could try to execute people with Zyklon B gas. Until that time, Zyklon B was used only to disinfect barracks which were full of insects, fleas, et cetera. I tried it out on some people sentenced to death in the cell prison and that is how it developed. I didn't want any more shootings, so we used gas chambers instead.

To Leon Goldensohn, after being asked about the invention of gas chambers, April 9, 1946, from "The Nuremberg Interviews" by Leon Goldensohn, Robert Gellately - History