24 hours absolute minimum. 72 hours per most civil defence authorities. 14 days for a designed shelter in a fallout zone.
And after that, it depends on how much of society is left.
But you also have to think about the time the shelter is on standby, and that might be decades. You don’t want by the time you enter the shelter to find out there is mold everywhere, the food is all expired and the fuel tank corroded and leaked.
And after that, it depends on how much of society is left.
But you also have to think about the time the shelter is on standby, and that might be decades. You don’t want by the time you enter the shelter to find out there is mold everywhere, the food is all expired and the fuel tank corroded and leaked.