You mean if they persist above STEL or TWA limits? No I haven't forgotten these things. This is what I work with every day. Gas detection and protection is what my company does.
The levels you're exposed to DO matter in comparison with time.
Have drills turned deadly? Yes. Do I necessarily want them pumping gas through the subway? No.
But to state that there's nothing to be learned from testing like this is silly. There's no way to adequately prep an area for dealing with a gas related attack without knowing the airflow in a confined space like a subway.