Poison Gas In WW2

There appear to be accounts that at Sevastopol and other sieges in the Crimea, that the German forces used a gas of some sort.
Could they have used tabun, chlorine, mustard, Zyklon B or some other agent. (maybe a kind of toxic smoke?)

Are there any credible sources who can confirm or deny the claims, and if confirm, which gas was used?

 

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The only thing on record that I know of is the total opposition of hitler to the first use of gas, against the advice of the O.K.H.
Sevastopol was a pretty bad place , the fighting was intense
I am no aware of any sudden cracking of the defences as would be the case with gas ,
there was a lot of underground passages and bunkers , some gasoline could have been used , or whatever ,
the german delousing stations had Zyrklon B for health purpose I don't know if somebody got a bright idea , doubt it ,the delousing stations were waaayyy back from the front
there is always weird reports coming from the front line , stuff is hanging around and get burned ,sevastopol was a big base , probably even had some soviet gas for all I know . everybody had them
soldiers fighting for their lives have a very feverish imagination , battle paranoia of sort ( they are all trying to kill me !! ...)
could be but I doubt it ,
if it had been used and worked , it would have been used again , that's a natural law of war , and it didn't


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Acctualy allegations were not about use in Savastapol but Adzhimuskai qarries near Kerch (the other side of Crimea) where huge numbers of soldier, wounded and civilians made their last stand (from 20.00 - 40.000 poeple in all). In Soviet and now Russian and Ukranian mithology this battle is en par with defence of Stalingrad, blockade of Leningrad and defence of Brest fortress and is one of the bases for their motto: "Never again will we let this happen" (very important if one wants to understand their actions during the cold war and even now).

Since fighting lasted for about 4 months I seriously doubt the use of poisenous gas as the defenders were completly cut off from supplies, water and food. I belive that they were simply blockaded and starved to death.
What is known about defence of Azhimuskai qarries is known from post ww2 soviet research from right after the war which tended to accuse german army to be like Einzats gruppen of SS (even if in some cases they did act like them).
The accusation of use of poissenous gas was learned from few survivors after the battle and fro diaries found in the qarries later.
It is understand that if gas was used it was Chlorpeckrin (in russian nomenclature; PS in British, Aquinite in Frenck and Klop (green cross) in German).

An interesting debate about use of combat chemical agents on eastern front is here:
http://forum.axishistory.com/viewtopic.php?t=102632

 

Perversely, the British Government were so concerned about the German's widespread use of flamethrowers that they threatened to use poison gas on the Germans. Notwithstanding this, the British Army then used flamethrowers on the German ! Although the German's used flamethrowers on the Eastern Front , of course, I am not aware of them using this weapon against the Allies on the Western Front.
BG