IMHO, underground bunkers/shelters should be considered very temporary, at best. Yes, given an unlimited budget, they can be made pretty well. But as stated, you gotta be able to breathe. If air can go in, so can other things, like gasoline. Even if there is a diverter for just such a situation, the fumes will permeate & spread. Even if the fumes were not ignited, you would smell them & WANT to get out, because you know your done & if they were ignited, BOOM is the last thing you would hear. The end result would not be pretty if the people were determined to get you out at all costs. The only way to have one that is indeed at a "secret undisclosed location" is to transport it from the maker yourself, at night, with it covered up & have the equipment to dig the hole & set it in yourself & not tell the maker where you live, pay cash & hope no one in your family accidentally lets it slip.
Nat Geo would be better serve the public by having a show that shows how to build a low cost storm shelter & ways to build houses stronger & safer to begin with.
