the gas they used in Gas chambers is Zyklon B.. not chlorine bro...
they started using carbon monoxide and moved too zyklon ....
the movie is inaccurate....
from wiki..
"At the same time Eddington receives news and grieves for the death of Marston among the 15,000 killed by German use of chlorine gas at the Second Battle of Ypres"...
the movie refers to use of chlorine gas in battles, not in gas chambers..
"The first killing agent employed by the German military was chlorine. German chemical companies BASF, Hoechst and Bayer (which formed the IG Farben conglomerate in 1925) had been producing chlorine as a by-product of their dye manufacturing. In cooperation with Fritz Haber of the Kaiser Wilhelm Institute for Chemistry in Berlin, they began developing methods of discharging chlorine gas against enemy trenches."
http://en.wikipedia.org/wiki/Chemical_weapons_in_World_War_I
