It depends on the amount of CS, but different people react to it differently. I went through the chamber a few times and while it was unpleasant, it just made my eyes burn a bit and made them water. Other people were knocked for a loop...that's fun to see.
That being said, I was using Easy-Off on my Briggs and Stratton project to remove carbon and paint...works great...now here's what not to do- with the easy off still on the piece, I wouldn't take it to a sink and spray it down with hot, steamy water while your face is directly overhead. CS wasn't as unpleasant....but the block looks great!
[edit] speaking of things not to do with East-Off (or "Aircraft Remover") don't let the stuff stay on your skin for more than a couple of minutes...better not at all. Who says? The second degree chemical burns on my knuckles say, that's who.