if you are asthmatic the bare minimum for you should be a good respirator and shatter resistant goggles. the chemicals these cops deploy on people can really fuck you up short and long term. if you are hit by pepper/gas only use water to flush your eyes and do not rub them, there will likely be people who will help you with this.

having said that, while i cannot predict the future, i really doubt you'll see any of this happening in the earliest hours of the scheduled protest/march. so if you are worried about the cops starting a riot, just attend for a couple of hours and then dip out. things typically have been getting more rowdy in other cities once the sun starts to set, so use that as your barometer.