Not necessarily in this case. With tear gas involved, unless you have a mask, you are going to be pretty useless in a firefight.
Not necessarily. Different people respond differently to different types and concentrations of irritants. I am practically immune to CN, but oleoresin capsicum puts me down. You also have to consider the amount of time it would take a dispensing canister to become effective in a large room such as a theater. There’s a window of at least several seconds in which to act.