Lots of good ideas here, looks like they are making pre-fab "storm shelters" with NBC filtration options available. Looks like a better solution than others I've seen, however they are a bit spendy, as the accessories they offer can be had elsewhere for much less. HOWEVER a 1" thick steel hatch + lift jack is hard to do unless you have a welder and plenty of time.
Gunco Member #10
The "original" Boltcutter Rivet Squeezers:
Project Pink - the Pink and Blue AK-74: