For the record I am also into holocaust doubting as any proper skeptic worth his salt should be...researching historical accounts for valid evidence and probable truth. So if you really want to know what Zyclon B was used for start a new topic.
There are no doubts about the horror of concentration camps but the scale and accuracy has been called into question by 'revisionists' seeking nothing more than the truth.
Perhaps you should watch "Shoah" - lots of primary source interviews, from those involved, very explicit, truly depressing...
I would like to see you start a thread about your stated doubts re the Holocaust.
And as to why you hold these doubts.
"Holocaust denial is highly discredited by scholars and is a criminal offence in Austria, Belgium, The Netherlands, France, Germany, Lithuania, Poland, and Switzerland."
So if you really want to know what Zyclon B was used for start a new topic.
Zyklon B - Wikipedia, the free encyclopedia
A Study of the Cyanide Compounds Content in the Walls of the Gas Chambers in the Former Auschwitz and Birkenau Concentration Camps
Summary - Zyklon B, a well-known insecticide used for fumigation and killing people.