General Discussion

There is also the issue of food and water. They better stock a lot. Depending on the immediate situation, it could be years to decades (or more) before any is available. Reverse osmosis systems might help with water but you might not be able to grow your own food outdoors for decades. Do you like tomatoes that glow in the dark? ... No they won't actually glow, but surely deadly to eat.
And then if bad enough to cause a "nuclear winter", it will be a really long time before the surface is livable.