I’ve known two families with fallout/blast shelters, both 1950s vintage. One was built in the basement of an existing house, and was strictly a fallout shelter. Cement blocks, and and a corridor entrance with two angles, something like the entrances one sees today in airport bathrooms. I don’t remember what they used for the ceiling, tho we used to play in it as kids. It had a hand crank ventilation system, which IIRC used a whale of a lot of arm power for the amount of air it moved.
Though its light weight and long shelf life are ideal for navigating harsh conditions, freeze-dried food is probably most famous as a cultural curiosity: Like many Americans, I discovered it in a museum gift shop, gawking at the styrofoam-like ice cream that astronauts used to have for dessert. More recently, I encountered it at a disaster preparedness convention in Raleigh, North Carolina, where smiling, gray-haired preppers manned tables piled with plastic bags full of vegetables, meats, and stews.