Suppose that there is nuclear fallout in your region of the country. Fleeing the area might be your first instinct. Think carefully before you make that decision. If you are caught in a massive traffic jam, in the midst of radioactive fallout, your car will not provide you with adequate protection. It would be worse than getting stuck on the roadway in a blizzard. Much worse.
If you are too close to the site of a nuclear explosion, you won’t survive. Somewhat further away, you’ll receive too much radiation in too short a time, and you won’t survive for long. You either can’t flee, or it won’t matter. But suppose that you are far enough away to survive, and the only threat is a limited amount of radioactive fallout. Then you might be better off hunkering down, than bugging out. So this raises the question as to which room in any building is safest from nuclear fallout?
It turns out that for a one-, two-, or three-story building, the basement is safest. If you have a choice of buildings, pick the one with the most stories above the basement. Fallout lands on the roof as well as the ground, so the further away you are from the radiation, the better. The basement of a three-story building is much safer than the basement of a one-story building.
If the building has no basement, the first floor of a two-story and the middle floor of a three-story building is a little safer. And an inner room is always better than a room with an exterior wall. If there is no such room and no basement, the room with the least exterior wall area is slightly better, but maybe you should seek a different shelter.
For office buildings, the same general principles apply. The basement is best, as long as it does not have a wall with the exterior (open air) on the other side. Inner rooms are better; there should be plenty of inner rooms in a large office building. And stay a level or two away from the top, and a room or two away from the exterior walls.
How much radiation is safe? When do you bug out?
0 to 15 mSv is a normal amount of radiation from background sources and medical tests per year. Safe.
At 50 mSv, you reach the NRC limit for occupational radiation exposure per year. Tolerable.
From 50 to just under 100 mSv, there is reason for increasing concern. The risk of cancer at this level is small, and there is no radiation sickness. But it may be dangerous for the very young, the very old, and anyone in ill health.
100 mSv is the threshold for harm to a developing prenatal child. Pregnant women and infants should evacuate prior to this level of accumulated radiation exposure, and preferably prior to 50 mSv.
From 100 to 500 mSv, there is an increasing risk of cancer, as well as some initial adverse effects in the most susceptible members of a population (young, old, sick, pregnant).
From 500 mSv to 1500 mSv, radiation sickness affects even the healthy, with greater harm for higher doses. It is worse to receive any accumulated dose in a smaller space of time, and somewhat less harmful if the dose is spread out over a longer time. But once you are over 500 mSv, adverse effects and an appreciable increase in the risk of cancer are inevitable.
Over 1500 mSv (1.5 Sv), the risk of death from radiation rapidly increases. Anyone in ill health could possibly die at lower doses, but above 1.5 Sv even healthy persons are at risk of death. By a level of 3.0 to 4.0 Sv, about half the healthy exposed population dies. Above 5.0 Sv, pretty much everyone dies.
How do you know what the radiation level is? The least expensive radiation detectors are passive models: RADsticker and RADtriage. A professional-quality active radiation detector (LCD readout; audible clicks) will set you back hundreds of dollars: Gamma Scout Review. I have all three. I recommend the RAD triage card. It’s about $30 (as of this writing; prices mentioned in blog posts are never guaranteed) and is the size of a credit card. It’s easier to read than the $5 RAD sticker, which is the size of a postage stamp.
The passive detectors read accumulated radiation exposure, which is what you want to know. And they are small enough to keep on your person. It’s the type of device used by workers in nuclear power plants to read their cumulative exposure. Not very expensive. Very valuable.