Alright, take off the tinfoil hats.
I was a "nuke specialist" in the military (we had nuke capable artillery). If it ever came down to using it, I was the guy that got "the call" to arm it and lob it down range and was also the NBC (Nuke, Biological,Chemical) specialist.
All of this stuff is bad, but it isn't as half as bad as most think. I liken it to a story that gets told through about the 10th person....the more people it passes through, the more extreme it gets.
Gas is gas, and Bio weapons are germs, that stuff is hard to keep concentrated in open areas. Only place I'd really be concerned about it would be at "ground zero" or the release of it in confined quarters( set-off within a structure, like a building, subway system, etc (anywhere with min. air exchange/turn-over)).
Like the suggestion with the duct-tape and plastic shrink-wrap, it's really effective in a sense of reducing the dosage amount that is received. Think of fire from smoke...you block the airways around doors and windows and you'll reduce the smoke that will enter and the smoke coming through the registers and other orifices won't be as much as without blocking notta.
Nope, didn't buy any myself. Best thing to do, if it ever happens, is to either "out-run it", or get "up-wind" from it. That's what I would do if ever faced with it.
Oldhat
I'd tell you guys more, but I'd have to kill you!..heheheheh