As far as French legislation is concerned, the minimum is set at 24 hours. Its walls, floors, ceiling would have retained portions of a gas which was highly poisonous to man. These cadavers could have been nothing less than saturated with the gas, just as the cushions, mattresses and blankets discussed in the same technical document on the use of Zyklon B would have been saturated also. These mattresses, etc., had to be taken out of doors to be aired and beaten for an hour under dry atmospheric conditions and for two hours when the weather was humid. When this was accomplished, these items were then heaped together and beaten again if the paper test revealed any further presence of hydrocyanic acid.
Hydrocyanic acid is both inflammable and explosive.
Three thousand people crammed into a space of 210 square meters. If one wishes to obliterate all trace of an installation which would be intrinsically quite sophisticated, it must be scrupulously dismantled from top to bottom so that there remains not one shred of incriminating evidence. If explosives had been employed, mere removal of the concrete blocks would still have left this or that telltale sign. However, all of the artifacts shown to tourists attest to the existence of crematory ovens rather than to anything else. The real gas chambers, such as those created in 1924 and developed by the Americans around 1936- 1938 offer some idea of the inherent complexity of such a method of execution.