What to do about a nuclear explosion
The first fifteen minutes, why taking your clothes off removes most of the contamination, and the 24-hour rule that decides who comes through it.
Of all the emergencies on this site, this is the one most people write off in advance — and it is the other way round: outside the immediate destruction area, what decides who comes through is a handful of simple actions in the first minutes. Fallout causes most of the preventable deaths, and it is also what an ordinary building protects against best.
The three steps, in order
The official protocol fits in six words and has not changed in decades because it works.
- Get inside. The nearest masonry building — brick or concrete, better than wood or prefab — and head for its centre or basement. If you are in a car, the car does not protect you: find a building.
- Stay inside. A minimum of 24 hours, unless the authorities order otherwise. This is where it is won or lost.
- Stay tuned. Radio, mobile alerts if there is a network, television if there is any. Instructions to come out, evacuate or regroup arrive that way.
Which building, and which part of it
Protection is called the protection factor and comes down to two things: mass between you and the deposited material, and distance from the surfaces it fell on — roofs, streets, terraces.
| Place | Protection | Note |
|---|---|---|
| Middle of a concrete basement | Maximum | Almost always the best option available |
| Middle floors of a tall building | Very high | Away from the roof and away from the street |
| Interior room of a masonry house | Medium | No windows, two walls |
| Ground floor next to the street | Low | The street is covered in deposited material |
| Top floor or under the roof | Very low | The roof is the most contaminated surface |
| Prefab home, caravan, car | Almost none | Find another building, even if it costs minutes |
Decontamination: the most effective thing is the simplest
If you were outside when it fell, you are carrying particles. Getting rid of them is fast and needs nothing special.
- Take off your outer clothing before entering the clean area. This alone removes up to 90% of the contamination. Peel it outwards, avoiding pulling it across your face.
- Put it in a plastic bag, seal it and leave it far away — a corner, a balcony, another room. Do not wash it with anything else.
- Shower with warm water and soap. Without scrubbing hard: irritating or grazing the skin makes it easier for particles to get in.
- Wash your hair with mild shampoo and nothing else. Conditioner can fix particles to the hair instead of washing them out.
- If there is no water, wipe exposed skin — face, hands, neck — with a damp cloth or wet wipe, and blow your nose.
The 24 hours: where that number comes from
Fallout radioactivity is not constant: it decays very fast at first and then more and more slowly. After the first few hours it has already dropped enormously, and after a day it is a small fraction of what it was. That curve is the entire reason for the stay-inside rule: you are trading the worst hours for the far less bad ones.
Inside the shelter, meanwhile:
- Do not use the phone for calls, use text messages: they use less network and get through when a call will not.
- Eat and drink only what was sealed. Same as in a nuclear accident: tins, fridge, bottled water.
- Do not burn anything in a closed space: no candles, no camping stoves, no generators. Carbon monoxide kills faster than the wait.
- Set aside a corner for contaminated clothing and do not walk through it barefoot.
When you are told you can come out
Coming out is staggered and ordered by the authorities, usually zone by zone. When your turn comes:
- Cover your skin the first time you go out: long sleeves, a hat, a mask if you have one.
- Do not raise dust: no dry sweeping, no leaf blowers.
- Go to the agreed meeting point, not house to house looking for people.
- Report to decontamination checks if there are any: that is where it is actually measured whether you are carrying material.
Manuals in this section
- The first 15 minutes after a nuclear explosion
- Decontamination: removing clothing and showering properly
- Where to shelter from fallout
If your concern is a nearby nuclear plant rather than a detonation, the answer is different and lives in nuclear accident.
Guides
- What to do in the first 15 minutes The flash, the delay before the blast wave, where to run, and why fallout takes a while to arrive: the minutes that decide almost everything else.
- How to decontaminate after fallout exposure Removing your outer clothing takes off up to 90% of the contamination. How to do it without spreading it, how to shower, and why conditioner is banned.
- Where to shelter from fallout, and for how long Which buildings protect and which do not, exactly where to position yourself, why the rule is 24 hours, and how to spend that time without the classic mistakes.
Gear that covers this
Products that match what the guide above recommends.
Affiliate disclosure: As an Amazon Associate we earn from qualifying purchases. This does not change the price you pay or the recommendations we make.
- View on Amazon
Battery or hand-crank radio
It is the third step of the official protocol: get inside, stay inside, stay tuned. With an electromagnetic pulse or the grid down, AM/FM radio may be the only channel still broadcasting.
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Water and food for 72 hours minimum
You do not go out for the first 24 hours, and possibly not for the next ones either. Without a reserve, hunger or thirst push you outside at exactly the worst moment.
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Hand-crank torch or spare batteries
A good shelter is an interior space with no windows — in other words, dark. Never candles: fire risk and carbon monoxide in a closed space.
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Heavy-duty sealable plastic bags
Contaminated clothing has to go into a closed bag and be kept away from you. It is one of those things nobody thinks about until it is needed and missing.
Frequently asked questions
Can you survive a nuclear explosion?
Outside the immediate destruction zone, yes, and what decides it is what the person does in the minutes that follow. Fallout causes most of the preventable deaths, and it is also the one thing an ordinary building protects against extremely well. Getting inside and staying inside saves lives measurably.
How long do you have to stay inside?
The general rule is 24 hours, and you come out earlier only if the authorities say so. Fallout radioactivity decays very fast in the first hours: after a day it is a small fraction of what it was at the start. That curve is the entire reason for the rule.
Is it worth going out to find my family?
No, and it is the most common mistake. Going outside while fallout is coming down means exposing yourself exactly when the dose per minute is highest. The right move is for each person to shelter where they are, with a family plan agreed in advance that says how you regroup afterwards. Schools and workplaces have their own shelter protocols.
Why should you not use hair conditioner?
Because conditioners and hair masks contain substances that bind to the hair and can fix radioactive particles in place instead of washing them away. When decontaminating, wash your hair with mild shampoo or just soap and water, without conditioner.
Does a basement really protect you?
A great deal. Protection is measured as a dose reduction factor, and depends on how much mass and how much distance sit between you and the deposited material. The middle of a concrete basement, or a middle floor of a large building, cut the dose by a factor of tens or hundreds compared with being in the street.