I'm pretty much in your position. Work a stone's throw from Ground Zero and commute by subway to Brooklyn. Right now all I carry is a couple of N95 masks.Remember the footage of the rolling waves of gray dust as the Towers fell? That's the scenario I envision.

I figure another likely scenarion is a bombing or fire on the subway or some disaster requiring me to exit a building in smoky conditions.I have been toying with the idea of buying one of the smoke hoods mentioned earlier. The one you identify looks pretty good, as well as the one from Aeromedics. The key is that it be light and portable enough that you actually have it on you when you need it.

As far as a suit or gas mask, I've pretty much discarded that idea for two reasons. For one, it is just too bulky to carry around. I carry various files and work related items as well as a small EDC. Much more and I am going to need to steal one of the homeless guy's shopping carts. (Though stashing a suit and gas mask at the office is a possibility.)Secondly, by the time you realize you are under attack and don the suit it may be too late, especially in the case of a gas attack. I think my time would be better spent identifying the source of the threat and heading away from it (preferably upwind).

I would think, looking at it from a terrorist's point of view, the easiest operation to plan and carry out would be a dirty bomb or a conventional (suicide?) bomb. Biological and chemical attack will probably be pretty far down the list because to do it well would be very complicated. It's not easy even for well funded and trained military units. Look at the sarin gas attack in Tokyo. All things considered, the casualty count was pretty low.

Above all, I try to practice what they call around here "situational awareness". Keeping my eyes open to the people around me, danger zones and possible escape routes.