Don't Panic:
A retired US military weapons/munitions/training expert has written this
explanation of chemical/biological/nuclear weapons, how the various
types work and how to survive attacks (and it's a lot easier than you'd think):
Bottom line on chemical weapons (it's the same if they use industrial
chemical spills); they are intended to make you panic, to terrorize you,to
herd you like sheep to the wolves. If there is an attack, leave the area
and go upwind, or to the sides of the wind stream. They have to get the
stuff to you, and on you. You're more likely to be hurt by a drunk driver
on any given day than be hurt by one of these attacks. Your odds get
better if you leave the area. Soap, water, time, and fresh air really deal
this stuff a knock-out-punch. Don't let fear of an isolated attack rule
your life. The odds are really on your side.