Wasn’t chlorine gas used in WWI? I know it’s nasty stuff: it will eat up your lungs. Fortunately, I don’t believe that simply blowing up the gas canisters would have been a very effective means of delivery. Still would have been nasty, especially in a crowded and/or confined area.
It is nasty stuff. I had an accident on my job back in ‘79 where a chlorine gas line broke loose and sprayed me in the face (Thank God for safety glasses). I still feel some of the effects of the half breath of the stuff I got.
Video from 2008:
www.longwarjournal.org/archives/2008/06/released_guantanamo.php
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WW1
http://www.firstworldwar.com/weaponry/gas.htm