When ventilation was not used such as in Crematoria IV and V (although a ventilation system was later installed in Crematorium V in May 1944), Sonderkommando prisoners wore gas masks when removing the bodies. When presented in court with a document by the chief Auschwitz architect SS-"Sturmbannführer" Karl Bischoff, Leuchter misconstrued aeration ("Belüftung") and ventilation ("Entlüftung") as part of the furnace blower systems, when they were actually in reference to the ventilation channels in the walls that straddle the gas chambers. These are visible on blueprints, and can still partly be seen in the ruined east wall of the Crematorium III gas chamber.