Strangely a ceremonial Red Cross car drives up with the cans of gas. It couldn't have been stored in an adjacent shed I guess. Maybe that's how you include the Yiddish penchant for irony (often seen on the holocaust scene): the irony of a Red Cross vehicle delivering death gas! Did that car just travel back and forth all day?
When the Auschwitz victims filed into the gas chamber, they discovered that the imitation showers did not work. Outside, a central switch was pulled to turn off the lights, and a Red Cross car drove up with the Zyklon. An SS man, wearing a gas mask fitted with a special filter, lifted the glass shutter over the lattice and emptied one can after another into the gas chamber. Although the lethal dose was one miligram per kilogram of body weight and the effect was supposed to be rapid, dampness could retard the speed with which the gas was spreading. Untersturmfuhrer Grabner, political officer of the camp, stood ready with stopwatch in hand. As the first pellets sublimated on the floor of the chamber, the victims began to scream. To escape from the rising gas, the stronger knocked down the weaker, stepping on prostrate victims in order to prolong their own lives by reaching gas-free layers of air. The agony lasted for about two minutes, and as the shrieking subsided, the dying people slumped over. Within fifteen minutes (sometimes five), everyone in the gas chamber was dead.
The gas was now allowed to escape and after about half an hour the door was opened. The bodies were found in tower-like heaps, some in sitting or half-sitting positions, children and older people at the bottom. Where the gas had been introduced, there was an empty area from which the victims had backed away, and pressed against the door were the bodies of men who in terror had tried to break out. The corpses were pink in color, with green spots. Some had foam on the lips, others bled through the nose. Excrement and urine covered some of the bodies and in some pregnant women the birth process had started. The Jewish work parties (Sonderkommandos), wearning gas masks, dragged out the bodies near the door to clear a path and hosed down the dead, at the same time soaking the pockets of poison gas remaining between the bodies. Then the Sonderkommandos had to pry the corpses apart.
Raul Hilberg. The Destruction of the European Jews. pg. 975-976. Holmes and Meier. 1985
I don't know much about gas masks. Hilberg mentions one with a special filter. Is that something where the gas is neutralized. Or do gas masks usually have some kind of compressed air that is released?
And of course that Hydrogen Cyanide (zyklon B) wouldn't sublimate so fast unless it was above 79 degrees fahrenheit (it's boiling point) is something extensively discussed on other threads.