Multiple countries around the world still have stockpiles of chemical weapons.
Some, like Syria and North Korea, have stockpiles that they haven’t declared to international regulatory bodies. This means that the possibility of you getting yourself stuck in a chemical weapons attack is more likely than you think.
If you have the proper equipment handy, surviving a chemical weapons attack should not be as difficult. All you have to do is wear the correct anti-chemicals attire and exit the area of attack as quickly as you can to avoid further contamination.
However, if you are not prepared, or if your equipment is at home and the chemical attack occurs while you’re out, there are still things that you can do to minimize the effects of a chemical attack. (Related: Over 100 years later Bayer still refuses to take responsibility for developing the poison gas used during World War I.)