Nuclear and Radiation Emergencies: What to Do
The same three steps apply to nearly every radiation emergency. They come from Ready.gov and CDC.
1. Get inside
Go to the nearest building and move away from windows. A basement or the center of a large brick or concrete building is best. A car is not shelter.
2. Stay inside
Close windows and doors and turn off fans that bring in outside air. Sheltering usually lasts at least 24 hours. Do not go out to collect family: schools and care facilities have their own plans.
3. Stay tuned
Follow officials on a battery-powered or hand-crank radio. Leave only when they say so, or if an immediate hazard such as fire, a gas leak, building collapse or serious injury forces you out. A short move from very poor shelter to adequate shelter nearby is different: see finding shelter.
Different emergencies, different risks
| Emergency | What it is | What changes |
|---|---|---|
| Nuclear detonation | A blast with heat, light, pressure and radiation, and fallout the wind can carry long distances. | Get inside the most protective building you can reach within minutes. Potassium iodide will not help. |
| Nuclear power plant accident | A release of radiation over an area, called a plume. | Follow local orders. You may be told to shelter rather than leave. Take potassium iodide only if told to. |
| Dirty bomb | Explosives mixed with radioactive powder or pellets. It cannot cause an atomic blast. | Get inside, and follow officials on when and where to get screened. |
Descriptions from CDC. Actions from Ready.gov and CDC, linked in each guide.
Tools and guides
- Fallout decay calculator
See how fast fallout radiation fades after a nuclear detonation, using the published t^-1.2 formula and the 7-10 rule. Sources and limits included.
- Potassium iodide reference
What potassium iodide does and does not do, the FDA dosing table, who should avoid it, and why it does not help after a nuclear bomb. Not a dose calculator.
- Nuclear fallout maps
Why no map can show where fallout will land in advance, how officials map it after a detonation, and what to do instead of driving by a map.
- Nuclear blast radius
The severe, moderate and light damage zones federal planners use, with distances for 0.1, 1 and 10 kiloton explosions, and what to do if you have warning.
- Radiation maps
How to read EPA RadNet and other radiation maps, why normal readings move around, and what a change does and does not mean.
- Geiger counter guide
What a home radiation detector does and does not tell you, how to read its units, and which specifications to check. We have not tested any detector.
- Finding shelter
We found no current official national list of fallout shelters. Here is what federal guidance counts as adequate shelter, and how to choose yours in advance.
- US nuclear plants by state
Reactor sites from NRC records, with a free dataset.