May I ask what kind of training was that?
A major point of the exercise is to instill trust in your gas mask and your ability to use it correctly.
When I did it, we put on our gas masks, entered a little building full of gas, stood around a bit feeling the tingle on our exposed skin, then one-by-one were told to take off the mask and try to say something (I think it was our name and rank), then run out.