If symptoms don't show improvement, a second shot can be given within ten minutes. There are also antidote tablets which can be taken preventively. The Swedish auto injector and tablets combined, provide the best protection until proper medical treatment can be given. That being said, the best protection is DEtection. This unit tracks deadly fumes right down to size of plume and where it is traveling.
Sensors work based on their ability to pick up compounds with a phosphorus-fluorine chemical bond.
An added bonus is that this new invention is much more accurate than currently used detection methods and gives much fewer false alarms. Generally what is available to the military and police trickles down to the populace, so eventually these too may work their way into public domain. And now the rest of the story. . .