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How Long After Nuclear War Is It Safe? (To Leave Shelter)

When people are preparing for the worst, nuclear war is often something that people love to study up on, just in case. If nuclear war is a pressing worry and seems imminent, how long will conditions be toxic and dangerous after the nuclear bombs go off? After doing extensive research, here are the best ways to know what to do following a nuclear bomb and how long its effects will last.

After a nuclear war, it generally takes at least 3 to 5 weeks on average for the environment to become safe again. It takes about 7 hours after a nuclear blast for the resulting radiation to start to go away. If exposure is severe, within a few months, people will notice negative effects on their health.

Of course, all of this depends on the bomb yield, how many bombs were dropped in your area, the wind direction and speed, as well as how close you are to ground zero. Therefore, this article will mostly deal with averages and should not be taken as gospel since there are so many variables in play.

Also, remember there has never been a nuclear war, and so a lot of this info is based on some science and some conjecture. Basically, all we have are mostly educated guesses. However, there is some consensus on timeframes, and that’s what I will focus on.

An illustration showing fire on a bridge and the devastation of a nuclear attack

What to Do Before and Right After a Nuclear Bomb

The initial shockwave of the explosion would decimate nearby buildings and damage structures further away with long-distance shockwaves. The best thing to do right before, during, and after the dropping of a nuclear bomb is to stay indoors.

This is because sheltering in a sturdy building will give protection from the nuclear shockwaves, radiation, and scorching heat. The centers and basements of buildings are the best places to stay stability-wise, and will protect you from the flying debris and toxic dirt that will be thrown into the air.

Fallout is the word used to describe radioactive particles in the air after a nuclear bomb is detonated.

Exposure to large amounts of nuclear fallout will create bad cell damage, radiation sickness, cancer, radiation burns, and even death. This dangerous nuclear fallout could potentially be carried by the winds and atmosphere to places that are far away from the initial bomb site.

By staying put and hunkering down in sturdy buildings, people who are at risk can shield themselves from this radioactive and hazardous fallout, which will luckily grow weaker and diminish as it travels further away and as time passes. Try to stay in a building that has thick layers of concrete, packed earth, or steel around it for the best protection.

The safest thing that you can do before and during a nuclear bomb strike is to find a shelter that you can spend up to several days in. While the nuclear blast and the resulting fallout are dangerous, having an appropriate type of shelter can help you avoid many of the initial dangers associated with the nuclear blast.

Shelters should be sturdy and should ideally have thick walls. Buildings built with plenty of concrete and steel, like schools or office buildings, are the best types of makeshift shelters that you will be able to find.

If you cannot find a shelter like this, you should try and find any form of shelter that you can. You should not shelter in your car if possible. The metal of the car is far too thin and does not block high levels of radiation. Your car’s windows will also be broken by the shockwave from the blast, which will make you even more unprotected while in your car.

Related How Much Does a Survival Bunker Cost? Build vs. Buy.

Mobile homes and exterior buildings like sheds also are not ideal shelters. If you need to move between shelters, do so after a couple of hours, as this will allow a majority of the active radiation in the blast area to dissipate before you go outside.

Generally, nuclear fallout expels half of its energy in the hour after it’s detonated, and 80% of its energy in the first 24 hours, so staying inside for at least 24 hours will significantly improve the odds of dodging the most dangerous effects of radiation. Keep in mind that this is a general rule of thumb, and these numbers can vary depending on the type of nuclear weapons used and where the weapon was detonated.

Family in home basement bunker or survival shelter safe room food supplies

How Much Time Needs to Pass After a Nuclear Bomb before it’s Safe Again?

After a nuclear bomb goes off, it takes around 3 to 5 weeks for conditions to become safe and stable again. This is because right after a nuclear explosion, lasting radioactivity will decrease to about 10% of its initial amount every hour.

Two days after the last bomb goes off, the residual radiation will lower to 1%. Although nuclear radiation decays pretty quickly with time, there are still risks of damage. From the first few days, nuclear fallout becomes safer, and most areas will be pretty safe for outside travel and further decontamination after 3 to 5 weeks.

One of the only problems is, depending on the power and strength of some nuclear bombs, some nuclear explosions are more dangerous than others, with some having lasting hazardous effects that linger for as long as 1 to 5 years.

Related Can Earth Recover After Nuclear War? (How Long It Takes).

How to Stay Safe Until Nuclear Fallout Goes Away

A Man and Woman in Gas Masks With a Nuclear Explosion in the Background

After a nuclear blast, there is a 15-minute window to find shelter before the nuclear fallout starts. Even if a person gets caught in the fallout, they can still find a safe place, remove their shoes and outer clothing layers, wash all exposed skin, and store the contaminated clothing far away.

After staying indoors for at least 24 hours, try to stay alert for information from any first responders. Although electric power, internet access, and cell service may be down, most radios will still be working.

After a nuclear tragedy occurs, make sure to remove contaminated clothing from your body and avoid touching your eyes, mouth, or face while doing so. Take a thorough shower with soap and water to remove any radioactive particles from exposed hair or skin. Remember to gently clean any pets that may have been outside when the radioactive dust was active by brushing their coats to remove harmful particles and then bathing them with soap and water.

Overall, after the last bomb of a nuclear war is detonated, you won’t have to stay inside as long as you may expect before it is safe to go outside again.

I hope this article has been informative.

Thanks for reading!

For more, check out US Nuclear Target Map: Most Safe and Unsafe Areas.