The Holocaust Historiography Project
Auschwitz, by J.-C. Pressac
Photo 6
Photo 6: South side
Photo 7
Photo 7: East end wall
Photo 8
Photo 8: North side
On the left from ground level to just below the chimney, bluish stains
can be seen on the bricks of the wall, showing that hydrocyanic acid
was used there ( in 1942-44) for delousing purposes. In a homicidal
gas chamber, the action of highly concentrated HCN was rapid and
intense (never more than 15 to 20 minutes), at a temperature below
27°C, then the room was aired or artificially ventilated to get rid of the
gas as possible and finally it was necessary to burn all the corpses, so
that it was at least a day before before a new cycle commenced. The
acid had time to attack metallic parts superficially but but did not have
enough time to impregnate and stain the brick. Conversely, the operation
of a delousing gas chamber used much lower concentration, of HCN.
but as a general rule and according to witnesses, the gas remained for
a very much longer time, from 16 to 18 hours, and a higher temperature
was maintained by heating the chamber by stoves (for example there
were three stoves in the BW 5b gas chamber).

From left to right on Photo 6: the outside entrance to the “dirty” air
lock of BW 5b, the chimneys for the stoves (probably three in all,
for on Photos 6 and 8 two additional chimneys can be seen low on
the roof which do not appear on the drawings), the two natural
ventilation openings on the roof and the two wall orifices of the
extraction fans (Photo 7).