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The unthinkable happens


The details of what happens after a nuclear weapon is detonated can be confusing.  In order to better understand the purpose of a fallout shelter we have provided the basics below.

The Threat

1. Initial Fireball Explosion

Upon detonation, the initial explosion creates a fireball that burns at 100,000,000 degrees.  Most everything within the radius of this fireball will be vaporized.  Depending on the power of the weapon, this fireball can be several thousand feet in diameter.

2. Initial Radiation

Radiation is created during the fission of the fireball.  Mostly Neutron and Gamma particles are created.  In most weapons (except relatively small) the following thermal pulse and blast wave exceeds the radius of the initial radiation, meaning you won’t have to worry about this radiation because the heat and blast will kill everything within the radius of this radiation first.

3. Flash of Light

The initial detonation and fireball creates a flash of light so bright that it can cause temporary or sometimes permanent blindness at distances up to 13 miles away on a clear day or as far away as 53 miles on a clear night.

4. Thermal Pulse

Next, radiant heat extending from the fireball spreads outwards burning everything in its path close up and starting fires and burning skin further out.

5. Blast Wave

The heat from the fireball creates a high pressure wave.  This wave expands outwards slamming into buildings and severely weakening them.  It also extinguishes many of the fires started by the thermal pulse.

6. High Speed Winds

The air behind the blast wave accelerates to very high levels.  Multiples of the most powerful hurricane force winds, upwards of 620 mph (A category 5 hurricane has speeds of 157 mph). This wind then tears apart the buildings weakened by the blast wave.  It also creates flying deadly debris, throws people and also creates damaging pressure within the human body such as within the lungs, abdominal cavity and ears.

7. Firestorm

After the winds pass there may be many individual fires.  Those created by the thermal pulse that were not put out by the blast wave and winds, as well as fires that were created from the destruction –pilot lights, gas stoves etc- igniting debris.  If enough fires exist they may coalesce into a phenomenon known as a firestorm.  The many fires heat the air creating hurricane force winds that are directed inward.  There was a firestorm after the detonation over Hiroshima.  Many experts believe that a firestorm is less likely now because modern building materials within a city center are less likely to catch fire.

8. Fallout

The initial fireball vaporizes all material within its radius.  This material turns to dust.  The nuclear fission happening within the fireball creates neutrons which are absorbed by this dust.  This makes the dust radioactive and it begins to decay by emitting Alpha, Beta and Gamma particles.  The intense heat of the fireball creates convection currents that draw all of this debris upwards.  This process is what creates the characteristic mushroom cloud.  Some of this material falls from the stem of the mushroom cloud and some of it enters into the atmosphere.

These particles fall back down to earth ranging from within minutes to hours after the explosion, some may even linger in the atmosphere for months or even longer.  After an explosion you most likely have maybe 10-15 minutes before fallout starts falling down to the surface.  This material clumps together in little particles creating a sand or pumice type material.

Upon falling back to earth, this material continues to emit alpha, beta and gamma particles.

The strength of the radiation decreases or “decays” over time.  7 hours after the explosion, the fallout is only 10% as radioactive as it was upon detonation.  2 days later, it is 1/100th as radioactive.  2 weeks later it is 1/1,000th as radioactive.

Also, to clarify the neutrons that are produced in the fireball are what makes the dust radioactive.  The dust then emits alpha, beta and gamma particles.  These particles have damaging effects with what they come in contact with but they do not make other things radioactive.

These Alpha, Beta and Gamma particles each pose a different threat level:

Alpha- These are the weakest.  Most can’t penetrate human skin.   They are not a significant threat as long as you avoid direct contact.

Beta – They can only penetrate about 1/8″ into the body.  They can be blocked by a sheet of aluminum.   Normal clothing can provide significant shielding.  The danger from beta particles is from burns from contact with fresh particles on skin and ingesting or breathing in particles causing burns inside the body.  These beta particles will no longer be able to cause burns after a few days of the explosion.

Gamma- These are the main threat from fallout.  They are also the primary reason for having a fallout shelter.  They damage chemical bonds within human cells.  The more exposure the greater the damage.  The damage affects the body in many ways.  With enough damage the cells can no longer reproduce and the body dies.  Exposure is measured in units called rem.

100-200 rem – Effects within a few hours of exposure include vomiting, diarrhea, fatigue; reduction in resistance to infection.

200-300 rem –  Lethal Dose to 10-35% of the population after 30 days

300-400 rem –  Lethal Dose to 50-70% of the population after 30 days

400-1000 rem –  Lethal Dose to 60-95% of the population after 30 days

1000-5000 rem –  Lethal Dose to 100% of the population after 10 days

Different materials shield against these particles at different strengths.  The halving thickness of packed soil is 3.6″ which means that the strength of the radiation is cut in half for each 3.6″ of packed soil that it must pass through to get to you.  36″ of soil lowers to 1/1000th the damage.  72″ of soil lowers the damage to more than 1/1,000,000th the damage.

Staying inside a home basement provides some protection, however, fallout will gather at the base of the house, as well as on the roof and other locations such as window insets.  Going to the middle of the basement will expose you to less radiation than being outside, however you could still be exposed to deadly amounts of radiation.

To summarize fallout – A sand like material falls from the mushroom cloud.  Exposure to it is deadly.  However, it becomes less and less deadly over time.  As well, you can shield yourself from it by putting a material such as soil between you and the fallout.

9. Nuclear Winter

Nuclear winter is a theory that expects upon nuclear war, hundreds of cities will be destroyed leading to hundreds of firestorms.  The soot from these firestorms could then gather in the atmosphere and block out the sun for an extended period of time.  This would lead to vegetation as well as animal life that consumes the vegetation dying in large quantities leading to mass starvation within the surviving human population.

As mentioned above, there was a firestorm after the Hiroshima blast.  Hiroshima was a city of many wood constructed buildings.  There are many who believe that because of modern construction materials within cities, firestorms are less likely and thus a resulting nuclear winter would also be less likely.

Hopefully we never find out.

The Protection

Initial Fireball Explosion

The fireball burns at 100,000,000 degrees.  There is not much chance that any shelter would survive within the several thousand feet radius of the actual fireball.  It is expected that most military bunkers would not survive such conditions.  In nuclear war, the expectation is that the main targets (where the fireball will be unleashed) are first US nuclear launch sites and other military targets.  And secondary to these would be cities.  More specifically, within cities the fireball would most likely be above the city center.  If you live in one of these places, the only real protection is to move.

Initial Radiation

As with the fireball, the only locations expected to be affected by the initial radiation will be military targets and city centers.  However, not even they need to worry about this initial radiation because they will be destroyed by the fireball first.  (If it is a small weapon, there may be area that is affected by initial radiation that is not destroyed by the fireball, however this would still be at a military location or a city center so the same solution of moving away from these areas still applies.)

Flash of Light, Thermal Pulse, Blast Wave & High Speed Winds

Anyone within a Fortress Survival Shelter that is not located within the immediate vicinity of a blast should be protected from the flash of light, the thermal pulse, the blast wave and their following high speed winds.  Our shelters are buried 6 feet below the surface so the force of these threats should blow past on the surface.


Alpha Particles- Alpha particles which can’t penetrate human skin are blocked by the soil above the shelter.

Beta Particles- Beta particles which are not strong enough to penetrate a sheet of aluminum are blocked by the soil above the shelter.

Gamma Particles- 3.6″ of soil cuts the strength of gamma particles in half.  This means that 10 of these “halving thicknesses” or 36″ cuts the radioactivity down to 1/1,000th the strength of the particles on the surface.  Our shelters are engineered to be strong enough to be buried 6′ or 72″ underground.  Since each halving thickness of 3.6″ of soil cuts the radiation down in half again, 72″ of packed soil cuts the radiation down to less than 1/1,000,000th of its strength on the surface.

Fallout coming in air supply- All air that is pulled into the shelter is filtered through an NBC or nuclear, biological and chemical air filtration system.  Several countries including Switzerland, Finland and Israel have laws requiring each home to have such a system.  We install these systems in our shelters.

Months of Seclusion

When speaking of protection, this factor may not come to mind, however we believe that it is a major factor and must be addressed and regarded as highly important.  Spending several months inside a confined space is very challenging.  You can imagine the problems that arise.  For this reason, our shelters are designed to be as home-like as possible.

Our shelters are made to look like rooms inside of a house.  They can include bedrooms, bathrooms, a kitchen, living rooms, office/work space.  We can install faux windows, that provide a soft light and further enhance the affect of being inside a home.

As well, our shelters provide substantial space that is designated for storage so that it is kept out of site.  This allows you to store many months worth of food and water without having to live in a space full of clutter.

All of these factors allow the passage of months to weigh less heavy.

Nuclear Winter

The real threat of nuclear winter is a period of time where there is no food.  The shelter provides a safe place to store food, water, seeds and protected secrecy from the starving masses during this period of “nuclear winter”.

Further, as mentioned in detail below, venturing out of the shelter is a strategy in managing exposure.  Depending on the severity of the radiation, you will still continue to come back to the shelter and live there for a considerable amount of time afterwards.  Having a shelter gives you a place safe from any lingering radiation.

How Long to Stay in the Shelter?

The big question.  How long to stay in the shelter?  Unfortunately there is not a simple answer.

There are over 300 different fission products that may result from a fission reaction.  These vary with some having half lives of fractions of seconds, while others have half lives of many years.  As well, different fallout particles are made up of different types of radioactive elements and thus vary in decay times ranging from seconds to years.  Other factors such as rainfall can create areas of varying radioactivity.  The rain can cause fallout to clump together in areas making them “hotspots”.  

All of this together means that there is not a clear, specific amount of time to stay in the shelter.  The best strategy is to wait at least one, but ideally two months before exiting the shelter.  This allows for the most dangerous levels of radioactivity to decay.  Then create a schedule for leaving the shelter gradually, monitoring and managing exposure as you do so.

To properly create a plan for transitioning out of the shelter you will need to get a radiation detector.  After the initial 1-2 months in the shelter you can then exit the shelter using the radiation detector to determine how much radiation you are exposed to.  After first leaving you may choose to leave the shelter for only half an hour a day to take care of needed tasks.  Then after another month, after the radiation decays further you may make it one to several hours each day.

Ionizing radiation breaks chemical bonds in your cells.  A little bit causes a little bit of damage.  More exposure causes more damage, causing worse and worse symptoms until eventually the cells die and can’t replace themselves.  You start falling apart from the inside.  Eventually your body can’t sustain itself and dies.  However, if you are exposed to low levels, and then manage further exposure, your cells can replace themselves with healthy cells.  So it is all about managing exposure.

A relatively “safe” level of exposure would be no more than 200 rems in a 6 month period.  For example, with your detector you would determine that the area around your home exposes you to 1/10 of a rem per hour.  Knowing this, you could spend 10 hours out a day and still not get to 200 rems in a six month period.  But as you move about, you would need to monitor for hotspots, because you might stumble upon an area that is exposing you to 10 rem an hour.  This would much more quickly cause the 200 rem of damage.

You would have to live like this for a few years after the blast, but fortunately, the danger would become less and less as time goes by.

During this time you would undertake several measures to limit your exposure:

  • Regularly sweep fallout away from trafficked areas.
  • Cut branches from plants over trafficked areas so that leaves cannot collect fallout.
  • Remove the first 1-3 inches of soil in trafficked areas because it may contain fallout.

Also, as another important point, food and water that was left outside during the period of fallout is safe to consume as long as it is sealed.  As stated above, the alpha, beta and gamma particles do not make other objects radioactive.  This means that if a bottle of water left exposed is sealed then it would be safe, but if it was open, it would not be safe because, radioactive fallout particles could have fallen into the water, and drinking it would cause those particles to enter your body.  But if it is sealed, then there would not be any fallout dust particles in the water.  Put another way, you don’t have to worry if the food or water is radioactive itself.  You only need to worry if it has any fallout in it.


Our shelters provide significant protection. However, they are not a 100% guarantee.

We have not detonated a nuclear weapon to test our shelters.

We cannot test our shelters against a nuclear detonation. We don’t know what will happen during nuclear war.

What we do know is:

  1. If there is a nuclear blast it is better to be underground than on the
    surface during the fireball, thermal pulse and blast wave.
  2. The American Civil Defense Association says that gamma particles are blocked by 3′ of soil and our shelters are buried 6′ deep.
  3. After a nuclear blast and the ground is covered in radioactive fallout, you don’t want to be exposed near the fallout.  You want there to be at least three feet of soil between you and the fallout, breathing air that has been filtered through an NBC filtration system.
  4. We install NBC air filtration systems used in Switzerland, Finland and Israel.  These companies certify that they filter out radioactive particles.
  5. We have been told by the manufacturer that the coal tar coating we coat the shelter with can potentially protect the shelter for over 100 years depending on the amount of ground water. We did not build shelters 100 years ago so we cannot guarantee this rating. What we do know
    is that this same coating is used on deep water oil platforms and other civil structures such as bridges.

To Reserve a Spot in Our Build Schedule Call (513) 276-3719


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