What to do in the first 72 hours after a nuclear warning

Picture an ordinary afternoon. Every phone in the office goes off at once, and the alert says there has been a nuclear explosion and to watch out for radioactive fallout. Many people would walk to the window to see what happened. Some would rush down to the car to pick up their children from school. Emergency guides say to hold off on both, because what helps most in the first minutes is simpler than it sounds: get as deep as you can inside the nearest building, and stay there.

The advice comes down to three words, get inside, stay inside and stay tuned, from Ready.gov, the preparedness site of the US Federal Emergency Management Agency (FEMA). It applies to every kind of radiation emergency, from a nuclear explosion to an accident at a power plant. In Thailand, the agencies to listen to are the Office of Atoms for Peace (OAP), which handles radiation, and the Department of Disaster Prevention and Mitigation (DDPM), which handles disasters of every kind. This guide takes a few minutes to read, and most of what you need is the same 72-hour bag many households have just packed for the storms.

Fallout comes down later than the blast, and that is your window

A nuclear explosion near the ground sucks soil, dust and debris up into the air. They turn into small, sand-like particles carrying radioactive material, known as fallout, which drift back down onto roofs, streets and anyone outside. The good news is that fallout does not arrive with the blast. After an explosion there are at least 10 minutes before the first fallout comes down, which is enough time to walk into the nearest sturdy building.

If there is a warning before it happens and you are outside, take cover behind anything that can shield you from the blast. If there is nothing, lie face down on the ground to protect your skin from the heat and flying debris. Wait for the shockwave to pass, then get into the nearest building quickly. Do not stand and watch from outside or by a window, because every minute outdoors is a minute in which fallout can land on you.

Three principles make sheltering work: time, distance and shielding. Think of the fallout on roofs and streets as a stove giving off heat all the time. Each concrete wall between you and that stove works like insulation. The more walls, the further you are from the roof and the outer walls, and the less time you spend outdoors, the less radiation your body takes in. Put simply, the more concrete between you and the outside, the safer you are.

The best shelter is the middle of a concrete building or a basement, away from windows

The safest buildings have brick or concrete walls. If you can reach a building with several floors or a basement within a few minutes, go there straight away. Underground car parks and underground train stations also give good shelter. In Bangkok, that means the basement car park of a mall or condo, or the nearest underground MRT station.

In a condo, leave any room with large windows or a balcony and move to the central corridor or the fire stairs, which have walls on every side. In a house or townhouse with no basement, choose the innermost room with the most walls between you and the outside, such as a bathroom in the middle of the house or a storeroom under the stairs, and stay away from windows. The CDC gives the same rule: go to the middle of the building or a basement, away from doors and windows.

Once inside, stay in that spot for the first 24 hours, unless there is an immediate danger such as a fire, a gas leak, a building collapse or a serious injury, or until officials say it is safe to leave. The reason is that radiation from fallout drops very quickly during the first day, so the first day is when staying inside helps most. Sheltering like this usually lasts at least 24 hours. In the meantime, close doors and windows, switch off extractor fans and air conditioners that draw in air from outside, and bring pets inside.

The hardest part is when your family is spread out, with children at school and parents at work, and every instinct says to go and fetch them. But going outdoors while fallout is coming down is the riskiest time of all. That is why Ready.gov advises learning the sheltering plans of your family's schools and workplaces in advance, so that on the day you know each person is somewhere safe, and you meet up once officials say it is safe to go out.

Taking off your outer clothes can remove up to 90% of the fallout on you

If you walked through fallout before getting inside, the first thing to do is take off your outer layer of clothing. According to CDC guidance, removing the outer layer of clothing can remove up to 90% of radioactive material. Take it off slowly and do not shake it, so the dust does not fly up. Put it in a plastic bag, tie it tightly and leave it in a corner away from people and pets.

Then take a warm shower, wash well with soap, and wash your hair with shampoo or soap but no conditioner, because conditioner makes radioactive material stick to your hair. Do not scrub hard or scratch your skin, and keep cuts covered while you wash. If you cannot shower, wash your hands, face and any skin that was not covered at a sink with soap and plenty of water. With no water, use a wet cloth or moist wipes. Blow your nose gently and wipe your eyelids, eyelashes and ears. Tap water is fine for washing even if officials say to drink bottled water, because anything that gets into water supplies is diluted to very low levels, the CDC explains. Clothes kept in a wardrobe or drawer are safe to wear.

Food that was inside the building is safe to eat. Food in sealed containers that were outside is also safe, as long as you wipe the container with a damp cloth before opening it. But wait for officials to say it is safe before eating vegetables from the garden, or food and drinks that were left uncovered outdoors.

Potassium iodide tablets are another thing people often get wrong. The World Health Organization (WHO) explains that they only stop the thyroid gland from storing radioactive iodine. They do not protect against radiation from the fallout around you, and they should be taken only when public health authorities explicitly say so, not bought and taken in advance. Adults over 40 generally do not need them, except emergency workers, and iodised salt is no substitute, because eating large amounts of salt is itself harmful.

Listen to the OAP and the DDPM on a battery radio

In Thailand, the lead agency for radiation is the Office of Atoms for Peace (OAP), part of the Ministry of Higher Education, Science, Research and Innovation, which oversees nuclear and radiation safety. In January 2024 the OAP opened the National Nuclear and Radiological Emergency Administration Center to monitor radiation threats, coordinate responses and run emergency drills, Daily News reported. The OAP emergency hotline is 1296, which takes calls 24 hours a day. For evacuation, shelters and general help, call the DDPM hotline, 1784, which is free and open 24 hours, or use its LINE account, @1784DDPM, according to The Nation.

The one channel every home should have is a battery-powered or hand-crank radio, because it keeps working when the power is out or other channels fail. While you shelter, listen only to announcements from government agencies. If officials tell you to evacuate, listen to the routes and shelters in full before you set off, and once you have left, do not go home until you are told it is safe.

Pack the same 72-hour bag and agree on two meeting points

Almost everything you need for a radiation emergency is already in the DDPM's 72-hour bag: at least 3 litres of drinking water per person per day, ready-to-eat food, regular medicines, a phone and power bank, a torch with spare batteries, a radio, and copies of your ID card and important documents in a waterproof pouch. Only two things need adding for radiation: a change of clothes for everyone in the household, and a rubbish bag for clothes you take off. Choose sealed food, water and medicine.

The other step costs nothing: agree on a plan at home. Pick two places to meet. The first is your home. The second is a place everyone knows outside your neighbourhood, in case you cannot get home that day. Then choose one relative in another province as a go-between, whom everyone can call to say where they are and that they are safe.

This weekend, on Saturday 7 or Sunday 8 November, there are three things you can do at home. First, save 1784 and 1296 in everyone's phone. Second, open your 72-hour bag and add spare clothes and a rubbish bag. Third, talk with your family about where your two meeting points are, and ask your children's school how it plans to shelter indoors.

FAQ

How long do you have to find shelter after a nuclear explosion?

Ready.gov says there are at least 10 minutes before radioactive fallout comes down. Use that time to get into the nearest concrete building or basement.

How long should you stay in the shelter?

Stay in the safest spot for the first 24 hours, unless there is a fire, a gas leak, a building collapse or a serious injury, or until officials say it is safe to leave, because radiation drops fastest during the first day.

Should you buy potassium iodide tablets to take yourself?

No. The WHO says to take them only when public health authorities explicitly say so. They protect only the thyroid, and iodised salt is no substitute.

Who should you contact about a radiation emergency in Thailand?

The Office of Atoms for Peace emergency hotline, 1296, and the DDPM hotline, 1784, which is free and open 24 hours, or LINE at @1784DDPM.

Sources

• Ready.gov: Radiation Emergencies
• CDC: Decontamination for Yourself and Others
• CDC: How to Self-Decontaminate after a Radiation Emergency
• CDC: What to Do in Radiation Emergencies
• WHO: Use of potassium iodide for thyroid protection during nuclear or radiological emergencies
• Office of Atoms for Peace
• Daily News: ‘ศุภมาส’ เปิดศูนย์อำนวยการสถานการณ์ฉุกเฉินนิวเคลียร์และรังสีแห่งชาติ
• The Nation: Bangkok and 61 provinces on alert for storms and flash floods
• The Nation: What's in your 72-hour emergency bag? DDPM lists 6 essentials