The Breath of Life mask is really nothing to carry. The package is relatively square, slightly longer in one direction than a Papermare Flair pen, and slightly shorter than the same pen (the pens are on my desk). The package is probably about 1/4 inch thick. Weight is 1.3 ounces, just weighed on the mailroom scale. It's like carrying a padded envelope that's about 5 inches by 5 inches.

As far as a nuclear blast, I'm kind of with your thinking as far as preparing for it. I've read some, but know it won't be easy.

The Breath of Life offers some protection from fire fumes and NBC elements. But it's a filter in a hood, and that's all it is. If you are in a fire with no oxygen, you'll still suffocate with it on.

A dirty bomb is my worst survivable fear. Staying put and awaiting the clean up would be a good plan, if you were out of the areas of immediate danger. If you cannot, get out and then get clean ASAP.