The US government recommends hiding in a nearby building, but not all of them provide much shelter from nuclear fallout.
Poor shelters, which include about 20% of houses, are constructed of lightweight materials and lack basements. The best shelters are thick brick or concrete and lack windows. Like a bomb shelter.
This infographic from a government guide to the aftermath of nuclear attacks gives a rough idea on what makes a building a good or bad place to hide from fallout:
Hiding in the sub-basement of a brick five-story apartment building, for example, should expose you to just 1/200 of the amount of fallout radiation outside.
Meanwhile, hanging out in the living room of your one-story, wood-frame house will only cut down the radiation by half, which — if you are next to a nuclear explosion — will not do much to help you.
So, what do you do if there isn't a good shelter right near you? Should you stay in a "poor" shelter, or risk exposure to find a better one? And how long should you wait?
Should you stay or should you go?
In his 2014 study, Dillon developed models to determine your best options. While the answer depends on how far away you are from the blast, since that will determine when the fallout arrives, there are some general rules to follow.
If you are immediately next to or in a solid shelter when the bomb goes off, stay there until the rescuers come to evacuate you to less radioactive vistas.
If you aren't already in a bomb shelter, but know a good shelter is about five minutes away — maybe a large apartment building with a basement that you can see a few blocks away — his calculations suggest hoofing it over there quickly and staying in place.