As usual, though, evidence of the "gassing" itself is lacking.
Josef Kramer is quoted as admitting to the killing of these 86 prisoners - but this is at a French military court in Strasbourg, but he was in British custody at this time?
In his testimony, he refers to both "crystals" and "salts" added to water. The calcium cyanide (which becomes hydrogen cyanide after being added to water) which extermanists believe was used, looks like a "fine powder".
(Not that Kramer's testimony is reliable elsewhere; he did a complete turnaround on the existence of "gas chambers" at Auschwitz.)
But could this room seriously have been used as a gas chamber? Faurisson writes:
It gets even better. Several years after the war, before both British and French tribunals, the camp officials of Ravensbrück (Suhren, Schwarzhuber and Treite) repeatedly confessed to the existence of a "gas chamber" in their camp. They even vaguely described its operation. Eventually, those who did not commit suicide were executed because of this alleged "gas chamber." The same "confessions" were given prior to their deaths by Ziereis for Mauthausen (Austria) and by Kramer for Struthof-Natzweiler (Alsace).
Today, one can see the alleged "gas chamber" of Struthof-Natzweiler and in the same place one can also read the unbelievable "confession" of Kramer. This "gas chamber," which is designated as an "historical monument," is a complete fraud. The slightest amount of critical spirit will be sufficient to convince oneself that a gassing in this small room, without any sealing whatsoever, would have been a catastrophe for the executioner as well as for the people in the vicinity. In order to make this "gas chamber" (which is guaranteed to be "in its original condition") believable, someone has gone so for as to clumsily knock a hole into the thin wall with a chisel, and thereby break four tiles. The hole was so arranged that Josef Kramer would have dumped through it the mysterious "salts" (about which he could give no further details and which, when mixed with a little water, killed within one minute!). How could salts and water make such a gas? How could Kramer have prevented the gas from coming back out the hole? How could he see his victims from a hole which would have let him see no more than half the room? How did he ventilate the room before opening the rudimentary door, made from rough-cut lumber? Perhaps one must ask the civil engineering firm in Saint-Michel sur-Meurthe (Vosges), which after the war altered the place which today is presented to visitors "in its original condition"?
A report finds no evidence of cyanide:
Isn't it true, sir, asked Christie, that Professor René Fabre, toxicologist, was asked in 1945 to examine the  corpses of people allegedly gassed at Struthof-Natzweiler, 5 kilometres from Strasbourg in Alsace and scraped things from the van and the alleged chambers where Kramer was supposed to have gassed people, and that the results of that report were that there was no poison evident in his analysis?
"I am not at all familiar with this report," said Hilberg. (5-981)
Was there, in your knowledge, the existence of a single autopsy report to indicate that the cause of death of one person was from the ingestion of hydrocyanic acid or Zyklon B?, asked Christie.
So this whole storyline of the gassing at Natzweiler seems questionable. If Kramer had come up with such a affective method why didn't he use it at Auschitwz or tell anyone about it?