Hitler was opposed to the use of chemical weapons due to its use against his unit during World War I. However he was prone to revenge fantasies, such as when he ordered the entire city of Paris destroyed and when he ordered Berlin to never surrender.
The question is what would happen if during one of Hitler's bouts of insanity towards the end of the war Hitler decides that the German people have failed him or death would be preferable to capture by the Soviets and orders the SS (its members having sworn personal loyalty to Hitler) to use chemical weapons against captured German cities and towns? Might this result in a less harsh settlement for Germany (especially if a civil war erupts) after the war by making it appear the Germans were victims of the war as well (as with Austria and Czechoslovakia), or would it result in an even more harsh settlement? How might the Western Allies and Soviets respond to the attacks, especially those inside Germany itself?