Yeah, the stuff we used was in crystal form, and we had to heat it on a gas burner to turn it from a crystal to a gas. It was usually deployed in a tent or hut no more than 3m x 3m for maximum effect. (This was what we used for NBC "Nuclear/Biological/Chemical" warfare training)
We had to test the seals on our masks outside (they never fcuking sealed properly) then stand in the tent for a few minutes with the mask on, then take the mask off and repeat a prepared statement, then we'd be allowed outside. By the time you got the mask off you were choking and half blind, and I saw guys who freaked out and just smashed their way outside.
The stuff used for crowd dispersal (protests, police riots etc) is a bit milder than what we used, it's designed to cause discomfort without any long term effects, whereas depending on the volume of the crystals we used, determined the discomfort/lethality. When you can't see your hand in front of your face, it's bad........ (CS gas can kill)