In my demented youth, I was exposed to tear gas on several occasions. My impression is that it is not very good for crowd control, where people are loosely distributed over a larger area. Use in such cases it is often have the opposite of the desired effect and seems more like a crowd teaser that agitate people even more and gets them one step closer to a riot.
If in a building being gassed, you will see 10-30% of all go for the window and some will jump whether you are on the 1st floor or the fifth. It's not like when you get shot at where you automatically hunker down. When you are exposed to large amount of gas you want to try to get fresh air, don't! Hunker down, take your hands as far away on your face as possible, you will sit and drool and tears will flow, that's fine, but do not touch your skin and try not to cough too much.Then it's "just" a waiting game. If you look in the news stories you will see that people have taken hours of this kind of hurt.
Finally a word of advice, if you are in a place where the authorities are using tear gas, leave the immediate area, go home. Have you come into a situation where you are in a house that is being gassed, you should probably consider carefully whether it is not a time to come out with your hands above your head.