I saw a lot of people scrambling for shelters from the blast, but I wonder how many of them realize that if they survived the blast that they would have to hunker down for 14 days to escape the most severest part of the resulting radioactive fall-out? If they come out too early there is a strong possibility of radiation sickness.
Without an air filtration system in the shelter they would die from the radioactive fall-out. They also would need 14 days worth of food and water and a chemical toilet.