What to do in a nuclear attack: the first 72 hours

The federal instruction for a nuclear explosion is three steps: get inside, stay inside, and stay tuned. The detail below comes from Ready.gov, CDC, and FEMA. Officials in your area may give different instructions for your situation. When they do, follow theirs.

The first minutes: the flash and the blast

If you see an intense, unexpected flash of light, take cover right away. FEMA notes that the flash can arrive seconds before the blast wave, which gives people a short window to get away from windows. Windows can break with enough force to injure people standing behind them, even miles away.

If you are outside, Ready.gov says to lie face down to protect exposed skin from the heat and flying debris. After the shockwave passes, go inside the nearest building as quickly as you can.

The first hour: get inside

Fallout is the dust and debris that a ground-level explosion pulls up and makes radioactive. It falls back to earth downwind. The most dangerous fallout tends to land within tens of miles downwind of the explosion and within the first few hours. Getting behind walls before it arrives is the single most protective thing you can do.

Where to go. Ready.gov says that if a multi-story building or a basement can be safely reached within a few minutes, go there. The safest buildings have brick or concrete walls. Underground parking garages and subways also work. If none of those are close, any building is safer than being outside. A car is not a shelter: CDC says cars do not provide good protection from radioactive material.

Once inside. Go to the basement or the middle of the building, and stay as far from the walls and roof as you can. CDC explains why: radioactive material settles on the outside of buildings. The shelter-in-place guide covers how to pick the spot in your own building.

If you were outside when fallout was falling. CDC advises carefully removing your outer layer of clothing before you enter the building, if you can. Removing your outer layer can remove up to 90% of radioactive material. If you must be outside and cannot get inside right away, cover your mouth and nose with a mask, cloth, or towel.

Close up the building. Close and lock windows and doors. If possible, turn off fans, air conditioners, and forced-air heating units that bring air in from outside, and close fireplace dampers (Ready.gov, CDC).

Bring pets inside. If you are told to stay inside, pets and service animals should be inside too.

Clean off: decontaminate yourself

If you were outside after the explosion, clean off as soon as you are inside. The steps below are from CDC’s self-decontamination guide.

1. Remove your outer clothing gently, so you do not shake dust into the air. Put it in a plastic bag or sealable container and set it far away from people and pets.
2. Shower if you can. Use warm water and plenty of soap. Do not scald, scrub, or scratch your skin. Wash your hair with shampoo or soap. Keep cuts covered.
3. If you cannot shower, wash your hands, face, and uncovered skin at a sink with soap and water. With no sink, use a clean wet cloth or a damp paper towel. Gently blow your nose and wipe your eyelids, eyelashes, and ears. Bag the used cloths.
4. Put on clean clothes.

Ready.gov adds two cautions: do not use household cleaning wipes on your skin, and hand sanitizer does not protect against radioactive material. Tap water is safe to use for washing even if officials later advise against drinking it (CDC).

If someone else arrives and needs shelter, let them in. CDC says sheltering someone who was outside can save their life without endangering your own. Ask them to remove their outer clothing before they enter, then wash.

First hour checklist

Get inside

• Get into the nearest sturdy building: basement, brick or concrete, or the center of a large building
• If you were outside, take off your outer layer of clothing before you go in, if you can
• Move to the basement or the middle of the building, away from windows, outside walls, and the roof
• Bring pets and service animals inside

Stay inside

• Close and lock windows and doors
• Turn off fans, air conditioning, and forced-air heat that pull in outside air; close fireplace dampers
• Bag outer clothing and set it away from people and pets
• Shower with soap and shampoo, or wash hands, face, and exposed skin
• Put on clean clothes

Stay tuned

• Turn on a battery or hand-crank radio, a TV, or a phone for official instructions
• Text instead of calling, to keep phone lines clear
• Plan to stay put for at least 24 hours unless officials tell you otherwise

The first day: stay inside

Plan on staying where you are for at least 24 hours. Ready.gov says to remain in the most protective spot for the first 24 hours unless threatened by an immediate hazard (fire, gas leak, building collapse, or serious injury) or told by authorities that it is safe to leave. FEMA’s planning guidance tells the public to stay sheltered 12 to 24 hours unless given other instructions.

The reason is decay. FEMA states that fallout gives off over half of its energy in the first hour and then continues to decay rapidly. Every hour you stay behind walls in that first day spares you the period when radiation is strongest. The how fallout works guide explains the decay in more detail.

If your shelter is poor. A single-story wood frame house without a basement gives limited protection. FEMA’s guidance says that when an adequate shelter is within about 15 minutes’ travel, people in poor shelters should move there no later than 30 minutes after the detonation, and people in somewhat better shelters should wait an hour or two before moving. Officials may also order early evacuation for people in poor shelters. If you cannot reach anything better, staying inside is still far better than being outside.

Food, water, and medicine. CDC says food and drinks that are sealed or were already inside are safe, including unspoiled food in the refrigerator or freezer. Wipe off containers that were outside before opening them. Drink bottled water until officials say other water is safe; water in a toilet tank (not the bowl) or a water heater is also free of radioactive material. Boiling tap water does not remove radioactive material. Keep taking your medications; wipe off any container that was outside.

Power and devices. Expect the power to be out near the explosion. FEMA says most battery-operated equipment will not be damaged by the electromagnetic pulse and should work after turning it off and on again, and AM/FM radios will still receive stations from outside the area. CDC adds: do not go outside to reset breakers.

Days 2 and 3: stay tuned and follow instructions

After the first day, what you do next depends on where the fallout landed, and only officials with radiation measurements will know that. CDC says radiation levels will decrease with time as you shelter in place, and officials will tell people when and how to evacuate, which routes to use, where shelters are, and how to bring pets.

FEMA describes sheltering as short term, followed by a staged evacuation of fallout areas once safe routes are identified and cleared. Depending on local radiation levels, the right time to leave can range from a few hours to several days. FEMA strongly discourages self-evacuation because it can expose people to fallout and clog the roads responders need. The evacuate or shelter guide goes through that decision.

Things to expect and do in days 2 and 3:

• Keep listening. Use a battery-powered or hand-crank radio, ideally a NOAA weather radio, plus TV, phone alerts, and officials’ verified social media. Text rather than call if networks are busy.
• Screening. Officials may direct you to a community reception center, where you can be checked for contamination, get help cleaning off, receive first aid, and register for follow-up.
• Leave only when told. Do not leave your shelter until officials say it is safe, unless you have a life-threatening condition or the building is unstable (CDC). If you evacuate, do not return until local authorities say it is safe (Ready.gov).
• Garden food waits. Do not pick or eat food from your garden until officials say it is safe.
• Expect a slow outside response. FEMA’s planning assumes no significant federal response on scene for 24 to 72 hours. Local officials lead at first, so the supplies you have on hand matter.

Get ready before anything happens

Ready.gov suggests having several ways to receive emergency alerts, a battery-powered or hand-crank radio, a spare change of clothes for each person, and a trash bag for contaminated clothing. Decide where your household will meet if you cannot get home.

Two next steps:

• Check how far you are from documented likely targets with the targets near me calculator.
• Work out where in your own home or workplace you would shelter, using the shelter-in-place guide, and stock it from the fallout shelter kit list.