Individuals selected prior to the initiation of the gas chambers typically experienced what?

The main component in a gas chamber is tear gas. it can give irritating effects on the person's mucous membrane.

getting inside a gas chamber is part of the army training. they get trained to wear and clear their gas mask. but some usually forget to clear it when they enter the gas chamber, they get nervous and forget the instructions.   they are suggested not to have a full stomach. they also have initial lectures on what a gas chamber looks like. 

Sir thomas more, venerated in the catholic church as saint thomas more, was an english lawyer, social philosopher, author, statesman, and noted renaissance humanist. he was also a councillor to henry viii, and lord high chancellor of england from october 1529 to 16 may 1532. i found this information on wikipedia