Your post reminded me of old WWII methods we were exposed to in basic training. We were “trained” in how to survive a gas attack by wearing gas masks and going into a building that had supposedly been gassed. Of course, that was only twelve years after WWII ended.
They were still doing that in the summer of 1978 at Ft Leonard Wood.
That same gas training I know for a fact continued at least until 1993, every soldier was required to go thru the gas chamber at least once every year.
You would enter the gas chamber and the instructor would brief that the command “GAS” meant immediately don your gas mask, you had IIRC 5-8 seconds to remove your mask from the carrier place it and the hood over your head and seal the mask to your face, the instructor would then command “GAS” and we would don the mask, at which point we spent about 5 minutes in the chamber, with the gas flowing all around us, those who did not properly don and seal the mask, immediately began gagging on the gas, those who performed the task correctly just stood around for the instructor to command “All Clear” at which point you could remove your mask, but the instructor never gave the “All Clear” command, he would say “OK you can remove your mask now”, and most failed to follow proper command instructions and removed the mask, and began gagging, because the proper command was “ALL CLEAR” nothing else.
Of course there was a great deal more to it than described above but that is the jest of it, I am pretty sure all military services still perform that training, the gas used back then was CS Gas, pretty powerful stuff, much stronger than what police use to repel a riot, plus you were in a very confined and tightly closed space, you can believe this, there was always a lot of gagging and puking going on in gas chamber training for those who failed to follow all training protocols, you could even call it torturous.