If you are using household concentrations you won’t generate enough chlorine gas to be harmful in a ventilated area, like outside. If you put it in a bag and huff it you are going to have a bad time, but enough to cause damage can be tossed into a mason jar, shaken, and thrown pretty safely.

The acid makes it rust in seconds instead of days though, instantly visible and quite permanent damage.

Well, a 1:1 mixture of chlorine bleach and vinegar should damn near instantly and permanently corrode the steel. Don’t breathe the fumes, but I have toyed with the idea of a squirt gun filled with instarust.

The silicon die could easily chip a tooth as well, the stuff is insanely hard.