radiation shielding materials

Nuclear Radiation Shielding Protection and Halving Thickness Values

Radiation shielding is a mass of absorbing material placed between yourself and the source of radiation in order to reduce the radiation to a level that is safer for humans.

The effectiveness of the material depends on:

  • the type of radiation itself and the energy thereof
  • properties of the shielding material (density is important)
  • the total thickness of the material used, based on radiation halving thickness values

Different types of radiation behave in different ways:

According to the NATO Handbook On The Medical Aspects Of NBC Defensive Operations,

“Gamma or X radiation constitutes the principal casualty producing form of ionizing electromagnetic radiation associated with nuclear explosions”.

In other words, Gamma and X-ray radiation are of primary concern.

The ‘Alpha’ particle (another type of radiation from a nuclear explosion) is also dangerous, but is hardly penetrable. It can be stopped by a single piece of paper, or an air filter (think of it as a heavy dust particle). It is carried by the wind currents (fallout) and eventually falls to the ground and ‘decays’.

Gamma radiation though travels at the speed of light.

Nuclear Radiation Shielding – Gamma & X-ray

To protect yourself from gamma radiation resulting from a nuclear explosion, there are three things to consider:


The less time you spend exposed to radiation the lower your dose.


Radiation decreases with distance in accordance with the inverse square law. This means that the further away you are from the source of the radiation, the less radiation you’ll be exposed to.


As ionizing radiation passes through matter, the intensity of the radiation is diminished. Therefore, to help protect yourself from radiation you use shielding. However, the material you use matters significantly; some materials reduce the intensity of radiation more than others…

Radiation Halving Thickness

Every material has a “halving thickness.” This is the thickness required to reduce the radiation intensity by half. 50%.

So if the halving thickness of a material is 1 inch, then a 1 inch thick sheet will cut the radiation to 50%. Two inches will cut the radiation to 25%, 3 inches to 12.5%, and so forth.

See radiation halving thickness materials chart below.

First, this…

Radiation Protection Factor

This brings us to radiation protection factor. Or protective factor.

A typical house will reduce the power of the radiation to one fifteenth of that outside – this is called a protective factor of 15. Shelters constructed of the right materials can give a much greater protective factor than this.

According to FEMA TR-87, Standards for Fallout Shelters, “The minimum level of protection for public fallout shelters is PF 40”.

CAUTION: Permanent home fallout and blast shelters described in widely available FEMA pamphlets have protection factors in line with the PF 40 minimum standard for public shelters in buildings. In heavy fallout areas a sizable fraction of the occupants of PF 40 shelters will receive radiation doses large enough to incapacitate or kill them later. Permanent shelters built specifically to protect against nuclear weapon effects should have PF values much higher than PF 40.

Gamma Radiation Shielding For Various Materials

How do we apply all this in order to get an approximate idea about gamma radiation shielding for various materials?

A halving thickness is the amount of material that will block half the gamma radiation passing through it. A halving thickness has a protection factor (PF) of 2.

If you add another ‘halving thickness’, the material will block half of the remaining gamma rays, leaving 1/4. This is a protection factor (PF) of 4. Another layer of ‘halving thickness’ brings it down to 1/8, or PF 8. And so on.

A radiation shield is characterized by its total ‘protection factor’. For example, a shield that only lets 1/1,000 (one one-thousandth) of the gamma rays through, has a protection factor of PF1000 (the modern day standard).

1 layer = PF 2
2 layers = PF 4
3 layers = PF 8
4 layers = PF 16
5 layers = PF 32
6 layers = PF 64
7 layers = PF 128
8 layers = PF 256
9 layers = PF 512
10 layers = PF 1024

Radiation shielding materials are commonly categorized by their ‘halving thickness’, which is the thickness of that material required to block half of the incoming gamma rays.

If we know the halving thickness, then multiply it by 10 for PF of about 1000 (1024).

Radiation Shielding Materials

Consider the following chart of materials which indicate their radiation halving thickness, and approximately how much to achieve PF40, PF300, and PF1000 protection.

I’ve sourced the (halving thickness) numbers from what I believe are reputable sources. Then, simply calculated the PF numbers. Note that some of these materials will certainly vary in density and therefore shift one way or the other. For example, wood. They vary in density. Concrete, same thing… depends on its density mix/profile.

Consult with a specialist for accurate determinations. This is for information only.

Radiation Halving Thickness Chart

Stone 2.211.717.622.0
Concrete 2.412.719.224.0
Aluminum 2.714.321.627.0
Brickwork 2.814.822.428.0
Sand 2.915.423.229.0
Packed Soil 3.619.128.836.0
Wood 11.058.388.0110.0

A few typical questions:

How Much Concrete To Stop Radiation?

Well, apparently, for typical concrete density, it would take about 24 inches (two feet) to achieve an approximate PF1000 modern-day protection factor (radiation reduced to one one-thousandth). It doesn’t ‘stop’ it. Rather, it’s greatly reduced.

How Much Dirt To Stop Radiation?

Based on the radiation halving thickness of packed soil, it would take about 36 inches, or 3 feet to achieve approximately PF1000.


While searching for data in this regard, I noticed that there are some discrepancies out there. However I have gleaned what I believe to be accurate for this report. Some of my sources include the following:

  • NRC.gov
  • Civil Defense League of Canada
  • Wikipedia

Nuclear War Survival Skills (Upgraded Edition) by Cresson Kearny

U.S. Armed Forces Nuclear, Biological And Chemical Survival Manual

Potassium Iodide Tablets

Anyone who is concerned about radiation fallout should have these:
>> iOSAT Potassium Iodide Tablets
(view on amzn)

does potassium iodide expire

Concerned about nuclear fallout and alpha particles? I recommend a CE / CBRN approved full face respirator mask. The following product from MIRA Safety is one good choice…

CBRN Full Face Reusable Respirator-Mask
(their storefront on amzn)

[ Read:

5 Nuclear Radiation Detector Choices

Gas Mask For Nuclear Fallout

U.S. Nuclear Power Plants – Safe Distance?

US Nuclear Target Map


  1. A fallout shelter is a wonderful thing but now let’s look at the missing link. Now, let’s say you are in a shelter with a PF of 1000 for radiation and and everyone is still getting very sick from radiation. You then ask yourself what have I missed in my build? Answer: I forgot to properly filter the air circulating thru the shelter. The air filter is actually in the same room as we are and has become highly radioactive from filtering the contaminated air. The air filter system itself must also be isolated from the room containing the occupants.
    The final question I have to ask is how long must I keep my family in the shelter. The time to remain in the shelter is ————- the subject of another article—— Ken, let’s have it.

    1. You might want to revisit the ‘time’ parameter above. By that I mean you have to be concerned with a form of radioactive ‘noble’ gases (although there is nothing ‘noble’ about these gases) that are produced by a nuclear explosion, and which may remain in the air (that you need to breath) at levels sufficient to kill you or more likely make you very sick (and later kill you) for as long as 36 hours. Your typical gas mask filter or N-95 is not going to mediate this … Only the best ‘filter’ systems ‘may’ (this is a big ‘MAY’) filter out this gas, but in high enough concentrations this radioactive gas will overwhelm even the ‘best’ filter system … and you will have no way of knowing if the filter is compromised. This is FACT. You are no doubt now running to look at the specs of your supposed ‘swiss’ filtration system. Or you think you are far enough away from them … keep reading.

      Let us think of defeating all of the radiation threats posed by a nuclear explosion as a systematic ‘process.’ Assumption = you somehow survive the neutron emission exposure (instantaneous), the thermal wave (that will BURN your skin and clothing) and the blast wave with your vision unhindered (big assumptions – but these are also predicated on ‘DISTANCE’) … Keep reading for further comment due to the character limit.

      1. Step 1. Get inside underground shelter within at least 60 minutes (SOONER IS BETTER) of the first detonation. Completely seal off 100% of the air to your shelter for at least the first 24 hours after the last ‘event’ that produces radiated gas. CAUTION = IF you seal your shelter off from outside air (or IF you turn OFF your filtration system) you and the other occupants of the shelter will immediately begin a buildup of CO2. Once the concentration of CO2 in the shelter air reaches 10% you are all unconscious within two minutes and then DEAD. That’s a fact. So, you will have to either monitor CO2 (with an ACCURATE and CALIBRATED meter) and vent the shelter appropriately (with you ‘swiss’ filter system that might not stop the radiated gas from pass through), or scrub the CO2 out of the air with the CO2 scrubber and cartridges that your uber expensive shelter builder did not install and told you not to worry about …

        Other possibilities … your filter system breaks, runs out of power, or becomes clogged … Not good. You have a plan ‘b’? Some of us have plan b, c, d and e. And we still are 100% aware that we are likely not getting out of this one alive … But I digress.

        Next, if you seal off your shelter from outside air, then feel free to think, you will need a supply of oxygen. Don’t have that? You are dead. You will need a properly calibrated O meter with threshold alarms and a way to regulate the introduction of 100% Oxygen into your shelter while you continue to monitor O levels. Otherwise, you suffocate. Don’t worry thought, the CO2 will kill you first, but that’s if the CO does not kill you first. How is that possible? Good, you are thinking now. By the way, are you pissed at our leaders now? You know, the ones that are supposed to protect us from this BS? You should be. Keep reading.

        1. But you ask, “I am not planning to generate CO in my shelter (no open flames or combustion). Okay so if your shelter is near an area that catches FIRE and things BURN (remember the nuke sets things ablaze), your shelter will be exposed to HUGE amounts of CO … which is heavier than air and will find its way into your ‘swiss’ filter system or any opening in your shelter (and even more so if you are only venting it and producing negative pressures inside). Congratulations you are dead. Only way to combat this is to seal off the shelter for three hours or so (time it takes most of the local structure fires to die out and produce LESS lethal levels of CO), but now you are back to the CO2 issue. And we did not discuss the issue of your own body exhaling CO, yep CO. Tiny amounts, but this becomes a math equation to a CO level that will kill you in an unvented small space. Other way to combat this is to monitor CO levels with a properly calibrated meter, and then scrub the CO out of the air as needed with your scrubber machine and specialized filter. What’s that you say? Again, the dude you sold you that $200K shelter did not install one of those? That dude is an idiot. But not quite as he got you to pay him $$$ for a shelter that will kill you. At any rate, these are the uncomfortable facts to get through ‘STEP 1.’

        2. TRUTH = 99.9% of folks near a nuclear event (even in ‘shelters’) will NOT survive a full-on nuclear war. Oh, you can bet our ‘leaders’ will try to. That’s their plan. They have tax-payer funded shelters with all of this (assumption mind you). They are no doubt reading this now and texting their shelter engineers to be sure they have the ability to control the air in the shelter. The system to do all this is simply in theory, but not so simple in practice, and if even ONE thing goes wrong (O levels, CO levels, CO2 levels) they are dead. Or if they are ‘ignorant’ of the radiated gas issue and relying on truly untested filters (what filter system is actually tested to filter radiated gas from a nuclear explosion?), and they inhale enough of it, then they are getting really sick in a few months or years, and again … DEAD.

          Step 2 – you need to be able to ‘LIVE’ underground (mostly) for at least two weeks, and more likely 30 days (a ‘transition’ to above-ground living occurs in the last two weeks based on radiation levels where YOU are located). That will kill most of the folks that survive the first 72 hours in their ‘shelter.’

          Step 3 – almost no one will make it to step 3. Sorry.

        3. And now for the ‘moving away from target areas’ solution … This is the king of fallacy to think that you will survive the entirety of an event like this by ‘moving’ to an area that you ‘think’ will not have fallout. Most Americans no longer know how to ‘think.’ That’s the first real problem, and there is no getting past that. But lets’ say the person was a classically trained thinker. That unique individual would also have to be almost a ‘master’ of all trades (not a ‘jack’ mind you, almost a master). You will need to have medical knowledge equivalent to AT LEAST the EMT level; know how to procure, store and purify LOTS of water; know how to grow, harvest and hunt your own food; know how to truly negotiate with other ‘non-thinkers’ who will be acting very badly and quite possibly NON civilized (as they realize they can now steal whatever they want with no legal repercussions – they have all been trained to HATE now – good luck). Chance of such a person surviving all of this past the one year mark? I would give you less than ‘Vegas’ odds. The house always win. And remember dude-who-thinks-he-can-‘move’-away-from-the-problem. Those ‘problems’ you moved away from, that manage to survive (the walking dead I call them because they all have lethal doses of radiation and will die of cancers shortly – if the latest ‘booster shot’ does not do it for them … ), they are now migrating to where YOU live, to take YOUR stuff and end YOUR life. Just like Mexicans coming across our border with NO ONE stopping them, these survivors are coming your way. How are you going to deal with that?

        4. Let us journey even further, if you are still reading. Surmise that you survive the initial holocaust and are somehow managing to equilibrate in ‘post-apocalyptic,’ no-longer-woke-and-now-unconscious Amerika. Gee, I wonder who sent those nukes? You realize we have an enemy (probably MORE than one mind you), yes? One or more of those ‘frenemies’ launched those nukes. Why did they do that? Gee, I wonder if they are sending ground troops? You think? Remember to THINK. ‘Sentite liber cogitare’ my wayward sojourner. Cause they are coming now to mop EVERYTHING up. Hope you liked playing hide-and-seek as a kid, or at the very least watched both ‘Red Dawn’ movies, because that is exactly what is coming next.

          And your chance of surviving that is next to zero.

          You want to be a prepper? That’s all well and good I suppose. But imagine for a moment, that all of us preppers took even 1/2 the time and energy we have invested, and FOCUSED it on PERMANENTLY unseating the ‘political leaders’ that have caused us to be in this untenable situation? I am not talking ‘insurrection’ mind you. But referring to the legal and legislative means of doing so, BEFORE they remove all of those means – which they are doing as you read this. THINK about the impact that would have. It is still not too late. Let’s demand that they stop the insanity they have created so we can go back to actually living with a semblance of peace and security. Because what we have now is literally on the brink of nothing but the end of civilization as we know it or can even conceive of it.

        5. Good Job Xiphos – I agree with your assessment, and have been trying to figure out away to make it all the way to step 4 – so far not much luck; the alternative to fix our broken system and the scum bags running it – I think that window of opportunity has already passed about 2 years ago or more. Plus as you mentioned we have a vast majority of Americans who do not know how to think; trying to educate them seems pointless. Especially since even pointing out simple things like 6 month old Babies don’t need corona vax so why would any rational person even consider doing so ? Only draws pre programmed mindless responses from them – So how are we to recover our country from such levels of extremely poor education and thoughtlessness? I just don’t see it happening. Some parts of South America may survive the coming holocausts, however moving there is not an option for most of us.

      2. Thanks for this post. Makes me wonder why I even try. Atleast I am 80 miles from the nearest target. For all that’s worth.

  2. So based on above a 12×12 room at the 24” thickness is ROM 240,000 lbs of concrete. That is a lot of trips to H0m3 Depot in the Prius.

    1. Haha… it would be easier to just move further away from a nuclear target area :=)

        1. Can anyone point to information which clearly says what a safe distance is from fallout outside a building without any heavy shielding? 15ft? 20 ft? I would have thought this info would be easy to find… how far does the dangerous radiation project through air?… for instance.. if I used tarps to quickly build lean-to’s around a house… causing radioactive particles to accumulate 15 feet away from the house (instead of directly alongside the foundation) … there must be a safe distance without heavy shielding

        2. Great question. I’ve been asking the same. If you are on the second floor of a house, you’ve got the roof to deal with but what about outside walls? Are you far enough away from the ground to no concern yourself with those?

        3. 20 feet? oh my… Its a LOT farther than that. Its not feasible to try to keep fallout away from a building – especially if you don’t have at least a week of prep to do so and insane sums of money to attempt it. To get to a safe level for most blasts you would need keep fallout hundreds of feet away on all sides AND above you. not 100 feet, but multiple hundreds of feet.

          By spending 1/100th of the time and money you could just make two retaining walls with a 3 foot gap and fill the gap with packed dirt, and then do the other walls the same way and add 3 feet of earth to the roof.

          You can look into it yourself using the inverse square law to help determine radiation at different distances, but please dont try to rely on that as a solution unless you happen to be in a skyscraper with a solid interior room at least halfway up.

    2. Good Job Xiphos – I agree with your assessment, and have been trying to figure out away to make it all the way to step 4 – so far not much luck; the alternative to fix our broken system and the scum bags running it – I think that window of opportunity has already passed about 2 years ago or more. Plus as you mentioned we have a vast majority of Americans who do not know how to think; trying to educate them seems pointless. Especially since even pointing out simple things like 6 month old Babies don’t need corona vax so why would any rational person even consider doing so ? Only draws pre programmed mindless responses from them – So how are we to recover our country from such levels of extremely poor education and thoughtlessness? I just don’t see it happening. Some parts of South America may survive the coming holocausts, however moving there is not an option for most of us.

  3. If I store food in my basement (with just wood frame house above for shielding), I assume the food becomes contaminated with radiation. Does the passage of time make it safe to use or is it dangerous forever?

    1. Your stored food will be fine. Gamma radiation does not affect that.

    2. Radiation kills living cells. Cells that are dead are still the same atoms and thus food if they have no alpha or beta particles I.e., fallout dust in them. So any food in a container would be fine.

    3. Anything covered may be irradiated, but it wont be radioactive unless the fallout get onto it.

      So if you have things in containers, they will be just fine to consume. Just be incredibly careful if the outside of the container has fallout on it. Wash that away and transfer the contents to a clean sack and keep the container far away. (This isnt an issue if you are inside and fallout has not breached.)

  4. Does the gamma radiation move in straight lines? If you are in a basement, below ground level, are you essentially safe from the radiation if the source of the radiation is at an angle that places the ground (> 36”) between you and the source?

    1. NJ74,
      Gamma rays pretty much travel in straight lines. Question arises when you try to pinpoint the source. If you look at a nuclear blast, your basement scenario might be good. But you also would be smart to take in the gamma emitters in any fallout afterwards. This is why a fallout shelter with 3′ of earth cover is smart.

      1. Well yes and no. I love those answers. Gamma radiation is REDUCED by having to travel at 90 degree turns, but not completely. It is reduced by approx. 90% with each 90 though. But remember that radiation doses are CUMULATIVE. And cumulative is the 500-lbs gorilla in the safest location of your ‘shelter.’

    2. Gamma radiation travels in the same way as light does, since it is part of the same (electromagnetic) spectrum. Diffraction and refraction can be discounted and the result is still accurate enough in this case. If you take the radiation from the fallout as “shining” in straight lines, that is good enough to determine the shielding level you have in any particular direction. Downwards is the major problem, since the MASS between you and the radiation source determines the attenuation. Three feet of earth sounds great, but how do you get it above your head safely, without danger of collapse ?

  5. A basement is not really that safe (better than nothing) as the fallout that lands on your roof will mostly pass through your house unhindered and give you a dose in the basement. Presuming your house is standard wood frame residential home. You really need shielding over you, though the distance from the source (your roof) to the basement will reduce your exposure slightly as well as the slight amount of shielding you receive from the wood, drywall etc.

    1. That’s why I am placing more dense materials above my shelter area and all around me in 15 inch sand walls/ceiling of a framed out room. Then off to side since I have a 3/4 buried basement. Have garage doors exposed on one side. Shelter is on opposite side of basement with plenty of material between me and garage door. In rual area, but Still will die. Just more time than most to make peace with my maker. Unless fallout isn’t too bad. Have Israeli chemical, biological, nuclear gas masks for first 24-48 hrs. Plenty of thick wide duck tape to seal doorways. Not too concerned about O2 since just four of us in large basement. Glow sticks for light. Plenty of MREs, can goods, non perishables and ration bars for after first 24 hrs. Also plenty of bottles water and 55 gal water heater for water. Have well I can eventually use with generator hopefully. Plenty of stored propane and gasoline. Plenty of guns and ammo. All good I guess, unless I’m not home when SHTF. Then I’m screwed….lol. So Putin/Biden please don’t push that button unless it’s between the hours of 6pm and 230am est. Monday-Friday.

    2. I have a 180yro house with a deep cold cellar 12ft below grade and 3foot stone walls above that. I am 24ft from the roof peak. just roofed it with steel, it has 3/4 OSB over 1inch of old growth hardwood. From there it drops through 12inches of insulation into the second floor, down to 1/2inch of pine boards and then 1/2 inch of drywall down to the first floor. then another 3/4 inch to reach the cold cellar ceiling. I have 12in thick wool blend soundproof insulation. I’m too old to run very fast, I’m planning on bugging in. In my 14 x 22 Cold cellar…..what more could I add above in order to reach the PF40 min? I get I need density, I could add more dense insulation or perhaps thick boards overhead. Is dense foam useless in reducing fallout? thx

  6. This article prompted me to further reading on gamma radiation. As Ken mentioned, it is only one of several forms of radiation, and only one of the many sources of damage, from a nuclear blast. That blast has to be on or close to the ground to emit gamma radiation that will harm people on the ground. As Ken says, gamma radiation moves at the speed of light. Within one minute or less all the gamma radiation has been expended from the blast. Gamma radiation will hit and pass through you at the same time as you see the flash. Other blast waves – sound, force, wind – arrive later, if at all. A dose of ionizing gamma radiation at the threshold level for tissue damage, 150 cGy (centigray), is to be expected at 2.8 km (1-3/4 miles) from the detonation of a 1 MT (megaton) bomb blast. Farther away is safer. (End of part 1.)

  7. (Part 2.) Gamma radiation is a photon, a type of light energy. It is not a material particle like fallout, and it does not make anything radioactive/does not cause matter to become an emitter. A ground or near-ground blast will turn certain metals in the ground radioactive and as as the nucleus of the material decays it will give off gamma radiation. Most gamma radiation dissipates within about 500 feet. So it’s best to keep clear of ground zero. Cosmic gamma rays (mostly from stars going nova) are reflected back into space by Earth’s atmosphere. A high-altitude EMP detonation likewise will not send gamma rays to the surface. Here are two main sources for relevant information:

    nuke.fas.org/guide/usa/doctrine/dod/fm8-9/1ch3.htm .. .. and .. .. acq.osd.mil/ncbdp/nm/NMHB2020rev/chapters/chapter13.html

    1. ..Most Gamma radiation.. depends on the energy of the photon. Some cosmic rays go all the way to the ground and go deep into the ground.

  8. In nuclear weapons of the size commonly held by the nuclear powers, the initial radiation pulse is not a concern as far as civilian survival is concerned. The size of the device, even the 400kT MIRV devices, means that the blast radius likely to destroy non-hardened structures (thereby killing the occupants) exceeds the lethal initial radiation burst radius. Not exactly good news but it does put it into perspective. IF you are far enough away to survive the initial radiation burst, you may STILL be in the lethal blast range. Not exactly good news either. The most interesting, and problematic zone is the area where the blast is the problem, with the possibilty of being trapped in the debris etc.

  9. Further to my previous comment, NukeMap is a good tool to find out which “zone” you are likely to be in. This is a good starting point to draw the conclusions on which to base any preparations you choose to make.

  10. I have heard that an EMP bomb will usually be used prior to thermonuclear weapons, approximately 20 minutes before blast. Will this type of power outage automatically start transfer switches of generator powered equipment for air and water filtration? If I have to find radio tubes and non-circuit board equipment then I am in trouble. Better to have a stationary bike with generator for air filtration.

  11. Tax Man,
    EMP result of bomb, not a separate bomb. No, to second question, it will fry any and all non protected electronics, as far as I’m aware.

    1. Got a small faraday bag for my radio with gov weather bands. Also bag for my Geiger meter

  12. From the dates, I a retired engineering boss, 24 nukes, add a few crude organizational thoughts to an excellent text. The three rules of survival are get out of the city, repeated. Some will be hit 10- 20 times, if we win. The keys are the size, bull’s eye errors, air burst (max damage radius) or ground burst (max fall out. Wind direction will be crucial). Most of the energy is expended in seconds; duck, cover, lay down facing away and protect your eyes from light much brighter than the sun. Make prior decisions with loved ones: coming to get you or not. We meet at X. Do not die struggling to meet some one who left town. Have a bug out bag with you. Alpha and beta particles are lethal inside but can be stopped by a face mask/T shirt. Never ingest them. They are in dust. Gamma rays are deeply penetrating, kill, but do not harm water or food. They all will come from fall out, sand and dust, depositing on all surfaces. Tape cracked windows, keep the dust out. Wipe it off, strip it off, wear a scarf, run to a distant trash can.

    Add 200 ft of air to the halfing dimensions against fall out, consider those shade trees leaves. Get in the basement, deep as you can for as long as you can, the first days after the last blast will define life or death. Dust on the roof is a problem for most single level homes. Electromagnetic Pulse is death on electronics but some small stuff may survive; wrap a few radios in aluminum foil, lay them about on different steel shelves.

    I pray a lot, for our nation.

  13. Can anyone point to information which clearly says what a safe distance is from fallout outside a building without any heavy shielding? 15ft? 20 ft? I would have thought this info would be easy to find… how far does the dangerous radiation project through air?… for instance.. if I used tarps to quickly build lean-to’s around a house… causing radioactive particles to accumulate 15 feet away from the house (instead of directly alongside the foundation) … there must be a safe distance without heavy shielding

  14. Downwind207, Catch my comment to this article re gamma radiation. That radiation hits you at the same time as you see the flash. For protection from radioactive particles, all depends. Type of fissile material used, type of detonator and warhead, distance from blast to ground level, type of material atomized by the blast, mineral content of the ground, weather, jet stream pattern, height that particulate matter reaches during blast, proximity of very tall buildings or mountains. Lots of variables. Best to do lots of reading if interested in the topic. Might invest in dosimeters or a Geiger counter.

    1. If you are ‘hit’ by the initial gamma and neutron discharge when you ‘see the flash’ … two things:

      1. You saw the flash? Hopefully not directly, but even indirectly you will likely have ocular issues. You retina(s) will be injured, and you may lose the ability to see well, or at all.
      2. If you were close enough to the blast to receive the gamma and neutron pulse, and the thermal or blast wave does not kill you (because you dove to cover or laid down in a ditch), then you have been ‘cooked’ with such high levels of radiation that you will be dead in days or weeks.

      Those are the facts.

      1. Sorry, those are NOT the facts. Ionizing radiation travels in straight lines and its intensity is subject to the same inverse cube law as visible light….doubling your distance from the source reduces the intensity by eight times. Just because you can see the flash does NOT mean you have been exposed to a dangerous levels of radiation. Try NukeMap to see how this works. As for fallout, the ionizing radiation it emits is reduced with time. The rule of thumb is called the 7/10 rule…for every seven hours that pass the radiation emitted is reduced to a tenth of what it was. That is why it is so important to get under cover quickly. The first particles to fall will be the most dangerous by far.

  15. Downwind207 asks an important question but unfortunately it has a harsh answer. Fall out shielding is simply a matter of matter of the heavy density of common materials such as concrete, and earth and uncommon thicknesses of solid metals, inches. Radiation passes essentially unhindered downward through the roof of a normal house, providing a Protection Factor of 1 -2 where 500 – 1,000 is desired. (Multistory buildings increase this with every added floor.) The distances in air are football field lengths, miles, irrelevant in most assessments. Thus it is vital that the air born fall out, dust, be kept out of the shelter area.

    1. I still want to know… if a pile of radioactive fallout particles was in the middle of a football field… how far away would you have to be so there were no dangerous level? 10ft, 50ft?, 100ft?

      1. Downwind207, You’re not paying attention. Saying “radioactive” is like saying “mammal.” How far away from that mammal do you have to be to be safe? That depends, is it a mouse or a mountain lion? Does it have rabies, scabies, or hungry offspring to feed? With radioactivity it all depends, and on a complex, interlinked set of facts and circumstances. And you haven’t even asked “for how long.”

      2. Downwind207
        I agree with Anony Mee. That if you had a Geiger counter you will know that “safe” distance. Since the “dust” can be made of material emitting any of 4 types of radiation, the safe distance will vary.

        If the “contamination dust “ was only emitting Alpha an inch away would be plenty.

        If the “contamination dust “ was only Beta a few ft away would be enough ( with only a few exceptions of high energy beta).

        If the “contamination dust “ was only Gamma it could take that whole football field.

        If the “contamination dust “ was only Neutron it might take a mile.

        In addition the volume of “dust” makes a difference. So you can see why there is no way to know without a detector.
        What I can say is it is a much bigger hazard to your health if you breath it into your lungs then it is on your skin. Keep as much off of you as possible and keep everything out of your body.
        I know this doesn’t answer your question but it may give you a place to start looking.

  16. I grew up near the sub base in Groton CT. Every now and then we would get something in the mail about what to do if there were a nuke war… I still have a newsletter which explained one of the safest places to be in a fallout situation is in a boat in at least 6ft of water. It said just get out of the cabin once an hour and rinse the boat off… in 6ft of water the radiation is dispersed enough so it is not dangerous… it was presumed the boat would have both a canvas cover for the area behind the cabin (like to keep rain out… often fitted with snap buttons) and that there would be a pump and hose to rinse the fallout particles off the boat.

    1. Can you attach a pdf of that newsletter? That’s an interesting idea.

    2. That is outdated info and to be honest I’m not sure wherever you received it from was legitimate, as we have known that breathing in any of the fallout dust just means you have particles in your body emitting radiation straight into your organs without a barrier to stop them. The water under you means nothing, since its not a barrier between you and the fallout.

  17. Situation: Victorian stone cottage, Blue Lias stone. 18″ thick walls. Foundation concrete. No idea how thick but guess pretty sturdy. No basement. Only possible safe place in centre of house ground floor. Not large rooms. Furthest from outside possible: 13ft from front, and 7′ 6″ from side (18″ thick) stone wall. Behind safe space, another 18″ thick wall, leading to kitchen 8ft wide, with an additional 18″ thick wall on opposite side. Downside -1 wood door leading through to kitchen which is sadly 3/4″ thick only.
    If I put thick (non biodegradable) garbage bags filled with dense earth outside against the wall (the 7′ 6″ distance from safe place) to 5ft height, how thick should that be? 3FT thick?
    Behind safe place leading to kitchen, would 18″ thick outer wall and 8ft kitchen ‘air space’ plus something like earth bags again to shore up the sad 3/4″ kitchen door create a survivable barrier against fallout particles? Survivable meaning no radiation sickness?
    Above -1 storey only bedroom area plus loft space approx.6-7ft high. 1892 build. Will be leaky re: air, though not rain water. Never modernised. Not insulated. Not my fault. Peppercorn rent as I am pensioner and landlord never does anything to help. 2 lath-and-plaster ceilings between roof and safe place. What are the hopes of reducing roof fallout direct line to safe place downstairs to safer levels? Should I just kiss my ass goodbye?

  18. Hi. May I ask to the experts/preppers… straight and concise…
    Aside the huge amount of information here, I can’t make the point about many issues.
    The fact: Living 40 miles away from a big town, the site of the blast. Shelter (good basement in old house) 70 miles from the blast, i.e. 30 miles from home.
    1) Time 0: better stay at home or leave? About 1 hour to pack everything possible. 40 min to reach the shelter. If staying, when leave?
    2) Car will run 1 hour after the blast?
    3) I think sometimes there is some confusion between direct radiation from the blast and fallout. Aren’t they very different issues, both in time, distance and persistence ? So, giving a time line, from what should I be afraid of in different moments ?
    4) I read food doesn’t become radioactive… Great. So, if i had eaten a bean can 2 meters from the meltdown at Chernobil, one week after, that would have been good for me?
    Thanks to everybody…

  19. I was thinking about fallout and the practicality of building an expedient shelter in case someone does something dumb, so I looked up “halving thickness” for radiation protection and found an article on this site from back in March. There was helpful information there along with some pretty grim commentary from Xiphos and that got me wondering–what does “surviving” a nuclear war actually mean? “Congratulations! You’ve just survived Total Atomic Annihilation™! What has he won, Bob?” What have you won?

    With typical disaster scenarios, there’s at least a temporary aspect. At some point, the world as we know it recovers. With nuclear war, there’s no return to normal to look forward to. You’re catching what’s left of “normal” in your particulate filter. If enough bombs are tossed, even simple stuff you took for granted is never coming back. You’ll be sitting in your shelter in Kentucky and suddenly realize, “I’m never going to eat a banana again,” or “I’m never going to get a scam call–or any call–on my cell phone again.” Beyond the shelter waits a lifetime of hard labor people in the 19th century knew, only your efforts will be crippled by radioactive isotopes lurking in the soil for a generation. You may have been careful during that first month, but you or anyone you were trying to protect may have unknowingly absorbed enough radiation to cause bone marrow to suddenly collapse months or years later, assuming you or they don’t succumb to something silly in the meantime, like pneumonia, tetanus, or snakebite. All of your efforts may also be spoiled in a firefight over a rumored stash of food…what have you won? (to be continued)

    1. The practical matters of survival are pretty rough, but they can be overcome by grinding through, but what of the spiritual aspects of survival? For those of a materialist outlook, survival is essential because death is nonexistence. It’s “game over.” Some materialists may say that life beyond Total Atomic Annihilation™ is pointless and nonexistence is preferable. As an Orthodox Christian, I have to think of survival more broadly. “He who tries to save his life will lose it and he who loses his life will find it,” and “what good is it if you gain the whole world and lose your soul,” pose a dilemma. The price of physical survival may well be spiritual death if one is required to become a hardened killer in a post-nuclear world, essentially beginning to experience hell before death. Our synod is not particularly large. It’s likely there will be few, if any, surviving priests and bishops. No services. No Sacraments. Without that spiritual structure, it is simple to fall into madness and delusion.

      There is a lot of information about how to survive a nuclear war, but nobody has really talked about how to die well in such a scenario. Driving to a target site to “smile and wait for the flash” is indistinguishable from suicide, except for the additional waste of gasoline. As a Christian, I must respect my life on the one hand, but be willing to accept suffering and death on the other. I’m not sure that there is any sin in doing nothing more than gathering in a local church–a monastery would be even better if one were close–and finishing in prayer and repentance. It isn’t martyrdom, but there’s a certain grace in it. It’s hard to stare into the abyss of the nuclear war scenario and find survival preferable to that.

    2. Fallout actually clears rather quickly as opposed to a radiation spill from a nuclear plant. Within a couple years there wont be any radiation issues to worry about, and you can go outside your shelter to do whatever you have to after just a couple weeks.

      If stuff like cobalt nukes go off, than yeah, we are pretty screwed. something like a 500 year half-life.

  20. Could someone explain exactly what kind of iodine and at what dosage for how long? Does it matter the brand? Amazon has a bizziliian kinds of potassium iodine. I have a very large family that I’m buying for!

  21. Reading these posts one can only conclude NO ONE REALLY KNOWS. It reminds me of the climate change issue. The world is ending in 10 years… Man is destroying the planet.. It is all settled science…. Basically it is all someone’s theory that is skewed to say what they want it say for or against. No one has been in a real life nuclear attack sans 2 cities in Japan. Some died, some lived, some wish they would have died. What really happens 5 miles from a 20 megaton explosion, what works, what doesn’t is unknown, it’s all theory or worse opinion. The only hard science that is definitive is what it takes to stop radiation. That is proven via testing. That is something you can work with. People work every day within feet of significant radiation in war ships and nuclear power plants. If you do nothing you quit, which is fine, that’s your choice, but God gave us the ability to fight to survive. Is building a fallout shelter akin to getting plans to build the ark, maybe maybe not. If you feel led to do it, follow the best scientifically proven advice and build away. Don’t let negative Nancy’s sounding like the world’s foremost experts tell you it’s pointless. Defeatist love miserable company. We are all going to kneel before the Lord at some point. Some us before others. Pray, Plan, Proceed.

    1. COMPLETELY agree…God only knowsl. I’m just trying to do what I can do WITHIN reason. I won’t build a shelter. I won’t live in fear. I will go through whatever just like covid….boosting my immune system and not being afraid to live and love. I’m just trying to determine what the dosage is for iodine, what specific kind, and how long to take it after exposure. Other than that I have always had emergency supplies for earthquake and weather and I’m not doing more than that. Don’t have a ‘bug out bag’, and will shelter in place for whatever my future holds.

      1. ioSat iodine. Comes in pack with the directions and dosage. Supposedly the best and it is relatively cheap. I think you need a pack per person.

  22. A lot of talented and amusing people on this site. You have given me great information, and you have also made me laugh. Thank you. My question, we live near the center of South Carolina, but our “retreat” home is in the mountains of North Carolina. Let’s say the morons push the buttons while I’m in SC – from what I’m reading here, it doesn’t sound like I’ll be able to get to my retreat. We have an old truck that should survive an EMP, but it sounds like the dust of the fallout will kill us. Would you venture from SC to NC immediately after the blast, or would you honker down for a couple of days and then try to get up there? Again, thank you.

    1. @we will survive
      It really all depends on where blasts are, you may well be fine if its nowhere near you, you can go to a site called nuke map it lets you play with size and location etc and uses common prevailing wind patterns in your area to show extent of fallout or damage etc,
      Worth looking at, i did and it took a whole lot of stress out of it.
      Live life

      1. Very cool map! Thank you. Trusting God will keep us safe, and that we will be in the mountains if all this happens! In the interim, I’m learning to live life!

        Again, thank you!

      2. hey Kulafarmer……this is Dave in Idaho. glad to see you’re still above ground. It seems a good root cellar and being at a decent distance from a target will increase your odds of surviving. The jet stream plays a factor too. We cant do much about air filtration except minimize the amount of dust we breathe. I guess it will all depend on how much fallout/dust we get from the targeted cities.

    2. Stay put for a few weeks in a shelter at your current location, then make your way to your safe location out of the city.

      If a single tree is in the way when trying to get to your retreat, you almost definitely wont make it in time, and you can bet that the roads will immediately be packed with people trying to flee.

Comments are closed.