Removal of Warning Gas predates Nazi Regime

By Richard A. Widmann-

We often hear the charge that the removal of the warning gas from Zyklon B was evidence of the homicidal intentions of the Nazis. Inconveniently, the issue of the inclusion or removal of the warning gas predates the Nazi regime.

Those interested in the subject are guided to the U.S. Public Health Reports circa 1931. One finds extensive discussion of Zyklon B as a ship fumigant in the United States and especially in the ports of San Francisco.

In regard specifically to the warning gas we find:

“Both of the warning gases which have been used with liquid cyanide produce a tear effect. The effect of the 20 per cent cyanogen-chloride gas is greater than that of 5 per cent chloropicrin, i.e., lachrimation is much more marked; and it is believed that, on account of the tear effect, a person unfamiliar with fumigation could escape from a small room containing hydrocyanic-acid gas with 20 per cent cyanogen chloride before inhaling a dangerous amount of cyanide.” (July 3, 1931 p. 1575)

In that same issue we find this discussion of Zyklon B:

“Zyklon-B is liquid hydrocyanic acid absorbed by an earthy substance called 'diatomite' and packed in strong tin containers. Cans are provided containing 15 grams, 120 grams, 480 grams, and 1200 grams of hydrocyanic acid with 5 per cent chloropicrin as a warning gas.” (p.1576)

Although there is much additional information in this and other reports we move to the July 17, 1931 issue for this discussion of “warning gas.”

“For the purpose of giving warning of its presence, it is customary to mix a lachrimatory gas with HCN. The gas generally used in the United States is chloropicrin, in the amount of 5 per cent or 10 per cent (by weight) of the HCN present.

There was reason to suspect that the presence of this warning gas might interfere with the lethal action of HCN on insects. Insects breathe through spiracles in the thorax and abdomen, which probably are contractile and capable of closure. It is known that insects apparently dead from asphyxiation may recover after considerable intervals of time. On these premises the theory has been advanced that the irritant warning gas may cause the spiracles to close, however, its poisoning by the HCN, so that upon the return of fresh air it recovers.”

It should be noted for sake of completion that the U.S. did conduct studies on the removal of chloropicrin and determined that it had no influence on the death or recovery of cockroaches.

The importance of this information is twofold:
1) Zyklon B was widely in use in the United States as a fumigant in the 1930's.
2) There was wide debate about the influence that chloropicrin (warning gas) had on the effectiveness of Zyklon B in the United States.

There is no reason to doubt that the Germans were similarly using Zyklon B and debating and analyzing the influence of the warning gas on its effectiveness. In and of itself the removal of the warning gas from Zyklon B is not evidence of a murderous plot on the part of sinister Nazi conspirators.