EMP 101: Part IV—Faraday Cages

Faraday Cage c/o jeddaniels.com

Faraday Cage c/o jeddaniels.com

We’ve established that an EMP incident will fry all electronics.  This occurs whether or not they are plugged in or turned on. This also affects automobiles, batteries, computers, medical equipment, etc.  Needless to say, in such an instance, life as we know it will change dramatically.   Even more distressing is the fact that the strike of an EMP is not likely to give any warning. You don’t see it. You don’t feel it. You are simply left with the sudden consequences and whatever preparedness you have on hand.  So, other than your preparedness supplies, your new best friend may be a Faraday cage.

In fact, with the knowledge of the protection that a Faraday cage can provide you, you may be able to enjoy nearly as comfortable a lifestyle as you did prior to any electromagnetic pulse. While being mentally prepared to live in the Stone Age may be helpful, it’s not necessary. Aren’t you glad? First of all, allow me to dispel some myths about Faraday cages—and boy, howdy, there are a LOT of them.

  • Whether or not your electronics are plugged in, how long of an antenna you’ve got on something, what voltage it is, or whether or not they operate with batteries—all non-protected electronics will be affected by an EMP.
  • Batteries will be affected, usually in the form of “shorting” as well.
  • Electronic phone systems will also be damaged.
  • Surge protectors are useless in the event of an EMP exposure.
  • Just because your car has rubber tires, it will not be impervious to the effects of an EMP.  Rubber containers are insufficient protection against an EMP.
  • And oh yeah—yes, your Faraday cages DO need to be grounded.  If it’s NOT grounded, then the Faraday cage merely becomes a reflector or an amplifier.
  • Yes, a microwave can act as a Faraday cage, but why in the world would you want to use it for that?  That’s just silly when you can make one simply.
  • Faraday cages do not have to be solid, thus the name “cage” instead of the oft misused term—“box.”  In fact, many of them that you can build yourself or will see on the internet will resemble a bird cage or a very finely meshed chicken coop wire.
    Copper Mesh photo c/o twpinc.com

    Copper Mesh photo c/o twpinc.com

  • Also, contrary to what you may see on the internet, a sheet of foil on a box will not protect you.  It’s not thick enough to withstand the pulse. However, you CAN protect your items if they are buried a couple of feet underground in every direction (up and sideways.)
  • Last, but not least, a car is NOT a Faraday cage sufficient to withstand an EMP incident. It has some similar components, yes.  Most cars made today consist of fiberglass and disjointed parts, not a continuous metal material.  In addition to that, they are on tires.  Tires on a car do NOT serve as grounding.  Folks are simply getting an EMP strike confused with a lightening strike.  Now, IF you had an old fashioned car that was made of metal, that had its tires removed, that was also attached to an Iron or copper pole and that was ALSO on dirt—not  gravel—then  yes, you may have a car that doubles as a Faraday cage. (Kind of like the old clunker my dad has out in his “back forty.”
  • The cages do not have to be solid, but they do have to be constructed continuously without gaps between the protective material.

There. Now that we’ve discredited 90% of the internet information out there, let’s continue.

Michael Farady photo c/o commons.wikimedia.org

Michael Farady oil, by Thomas Phillips. photo c/o commons.wikimedia.org

Faraday cages are named after Michael Faraday who invented them in 1836. They block out external electrostatic fields and electromagnetic radiation.  One mistake many people make when it comes to an EMP is to compare it to a lighting bolt.  The effects of an EMP and a direct lightening bolt are very similar, but they are not at all similar in terms of their visibility, and affect on the body. An EMP is more like a radio wave, not a visible bolt of light or electric current. It’s the substrate layers of the diodes and transistors that make them susceptible to a magnetic pulse attack. Electronics are made up of diodes and transistors and substrate layers. A computer, car, television, and cell phones are made up of tons of transistors. When hit with a powerful magnetic pulse, the substrate layers are destroyed. However, early 1960’s and before electronics did not use substrate layers. They used vacuum tubes.  This is why older electronics are less susceptible to damage. This is why a human or animal body will not be affected.  Yes, our bodies consist of an electric volt. But understand there’s a difference between electricity and electronics. I just want to reiterate this again.  It’s important that any Faraday cage that you plan to use is grounded.  It has to be grounded in order to disperse the energy. What you should know though is that a Faraday cage is not fool proof.  The higher the frequency of the magnetic pulse, the faster it is. This is what causes the burn out.  The cages must be grounded, continuously connecting, and the openings of them cannot be too large. Chicken coop wire would work, but only if you double or even triple layered it as the opening are too large. For a reference of opening size, look at the front of your microwave door.  It’s a small mesh.  Just a like a snake can slither its way through the right sized hole, so can an electronic wave.

Galvanized Trash Can photo c/o housewares.hardwarestore.com

Galvanized Trash Can photo c/o housewares.hardwarestore.com

You can have an instant Faraday cage with a galvanized trash can or a large stock pot like they use in restaurants. (Be sure to clamp the lid down. Remember—continuous connection is key. Since Faraday cages are not fool proof, depending on the strength of the pulse, I would recommend burying such containers 2 feet under the ground, storing survival electrical and battery items. (Including batteries). An easy way to make a Faraday cage would be to acquire some 2 x 4 brass mesh sheets. (Mythbusters on the Discovery Channel did a couple of experiments using this successfully.)  Make a box frame with the 2 x 4's and staple the brass mesh to the outside. Create a securely attached/connected access entry within the frame. Solder a ground wire to one of the corners and ground the cage.  Scrap metal and mesh wires can easily be obtained in junk yards, on E-bay, the clay modeling section of a craft store, or at your local hardware or  “farm and feed” store.  The important aspect of this to remember though is that mesh or sheet metal only shields magnetic fields if the frequency is up in the RF range. To properly stop the wave, you need some iron, steel, or some slabs of thick copper.  Most electronics are useful in the VHF/UHF/SHF range today and will need more substantial protection.  Remember when you’re browsing the internet.  Protecting against sparks is not the same as protecting against a strong magnetic pulse. You can make your “cage” as small or as large as you’d like.  It wouldn’t be out of the question to continuously line a basement storage room or hole in the ground with copper mesh wire and a grounding rod. Bottom line, with an appropriately constructed Faraday cage, you can likely protect that which is inside from the electromagnetic attack of an EMP incident or solar flare, thus preserving the function of all that is contained therein.   Here is a very simple example of how Faraday cages work.  (DO NOT try this at home, please) Note that the Peeps are put into a mesh bowl and covered with a mesh cover. They are then put in the microwave.  The one Peep that wasn’t put in the microwave met his untimely death, while the others were still intact. For a little bit of a science lesson on the workings of a Faraday cage, check out this YouTube link. The science professor is EXCELLENT.  Note though that he does say that a car is a Faraday cage, however, I want to reiterate that it is NOT sufficient to extinguish the effects of an EMP attack.

Photo c/o physics.umd.edu/

Photo c/o physics.umd.edu/

Be selective in what you protect. It makes no sense to protect a cell phone, for example, as the cell towers will be useless.  If it were me, I would protect radios, communication devices (such as a HAM radio), batteries and all of their respective tools, thumb drives loaded with all of my vital information, and a laptop.  Keep in mind that a Faraday cage should be your LAST concern in terms of protecting every electronic that you enjoy presently.  It’s not like if you preserve your television you’re going to have any “juice” to plug it into.  Don’t focus on a Faraday cage and its time, effort, and expense at the risk of neglecting food, water, and medical supplies. It would be better for you to read up on solar power, wind and steam energy instead. EMP 101 Series


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Um... Kellene, I was responding to the part where Alt says "since they have no circuitry will withstand an EMP without any protection". I wanted to ensure that they understood that the point is to protect them...

Um... Alt, you could have a hand in a microwave for 2 seconds and not have any noticable effects. Sailors used to take smoke breaks in front of RADAR Antennas because it warmed them up (by cooking them slowely from the inside).

The radiation in a microwave makes a CD-ROM look like a spider-web of char and plastic almost instantly.

Stop "Um..."ing me. Everything you say like that is read with "attitude".

Just trying to help here, folks. You've made your point: consultum non grata.

Um, Chad... ever put your hand inside a microwave oven for 2 seconds? I hope not ... yet your hand won't be a burned mess after an EMP strike. (let me give you a hint, it has something to do with the intensity of the EM energy.)

Even outside of a Faraday cage a CDROM/DVD will survive an EMP (no sensitive circuitry/transistors to fry) A word of caution though, some cheap CDROMs don't last more than a few years under optimal storage conditions. Buy quality media.

My personal preference is a hard copy of anything I may need or want (documents, photos, etc...) stored in a fire resistant safe.

Chad, you make me laugh! I'll be careful how I use my "ums" in the future. They are more of a sheepish introduction to what I'm saying, as if I'm not sure you meant what I read, but I'll respond anyway... At least that's what they mean here on Venus. :-)

My "um" was supposed to be with attitude in response to your know-it-all attitude which is propagating misinformation here on a blog I enjoy reading. I'm no expert, but I've had some instruction on electro-magnetics and understand how it works.

You're comparing apples and oranges, the energy density inside a microwave is much greater than that of an EMP (though a Faraday cage can shield from both.)

EMPs cause high voltage concentration not high energy concentration. The high voltage quickly shorts out any sort of micro circuitry, it doesn't take a lot of energy to fry them.

There is metal in CDs and DVDs, but they aren't at any more risk of damage from an EMP than the layers in a roll of aluminum foil are at risk of fusing together.

In addition to that, the duration of an EMP is much less than the "...almost instantly." you mentioned. EMP duration is sub-millisecond (on the order of nanoseconds, in some cases.) As a result, even less energy is absorbed by conductors than in the case of a microwave.

I quickly found one source that states that CDs and DVDs are immune to EMPs through Google. Do you have any reliable sources stating otherwise?

To summarize: CDs/DVDs are EMP safe. I still feel paper is a better option for long-term reliability reasons.

Thanks for clarifying, Kellene. My babelfish is broken :).

Great article, by the way.

Explain Grounding....like if you have an old microwave that's broke, can you plug it in to ground it through the outlet? Or if you build a box like pictured. Thanks!

I'm planning on using my old laptop for storage purposes only, and keeping it in either a Faraday container or a galvanized trash can. Keeping extra batteries in the container is a great idea!


Grounding to the car won't help you. YOu'll need to ground them to the ground. The tires on a car won't help in this instance. It's very different than lightening.

Instead of using "thumb drives loaded with all of [your] vital information" I suggest you use optical storage (DVDs or CDs) They're cheaper and since they have no circuitry will withstand an EMP without any protection.

Of course in either case, you'll probably want something that can read the files off of your USB drive or DVD/CD. I think I might be putting an old laptop in an EMP safe place as well as a way to power it.

Ever put a CD-ROM in a microwave for 2 seconds... or even .5 seconds? It does not yield optimum performance. Makes a lovely coaster, but is useful only for that, or other purely aesthetic purposes.

I wouldn't keep everything on an unprotected CD-ROM/DVD.

Hope this is helpful.

Come on boys, let's play nice. By the way, something that I haven't discussed as of yet is that there's actually 3 levels of EMP strike that we can expect. E-1 to E-3. The E-1 is fast, but less infiltrating. Where as the E-3 is more widespread and slowly fries. I'll address that in a future blog.

1. Yes, as long as whatever is being protected is completely surrounded with good, conductive metal that is then grounded properly.
2. Fine as long as it fully encloses what is being protected and is properly grounded. Might be wise to use two layers at a minimum.
3. Metal garbage can, okay. Mesh wire will generally not work unless it is very small mesh (chicken coop wire wouldn't work). Yes, can be grounded properly to grounding rod.

Unfortunately, I have yet to find a quality "shaker flashlight" that provides suitable light. Everyone should be sure to actually USE the items which they store. Otherwise they will discover that that "100 hour light" has barely enough light to light the next one with.

A good idea of something to keep in a Faraday cage is a shake flashlight that powers itself when you shake it. These would be very useful, especially if it takes a year plus to restore power to where you are, etc., and batteries only last for so long.
Faraday cages would also be useful if kept in the trunk of your car with flashlight, radio, replacement car stuff, etc., if an EMP struck while you were traveling and not very close to a city or town. It would also be good to stock your trunk with other necessary things like water, food, blankets, first aid kit, (maybe even a small gun for extreme emergencies, just think of the Chris Stewart series) but not so much stuff that it takes up very much room, of course.

I am trying to figure out how to protect a radio and batteries in my car. Could I protect them in a cage grounded to the car's body and drag a chain attached to the frame?

Was there a change that occurred in cars in 1968? The reason I am asking is that I am looking to buy and old truck (late '60's to mid '70's) specifly for the reason that it would function in the event of an EMP attack or solar flare. I would guess that if it doesn't have a an electronic ignition it would start assuming that it is all original factory parts under the hood.

Three questions:
1. What about a four drawer metal filing cabinet as a Faraday Cage?
2. I also found heavy duty aluminum foil (3.48m). How effective would it be?
3. If I had a laptop in the garbage can, would it need additional protection, such as wrapped in mesh wire? And should that wire be grounded to the garbage can (which is connected to an outside ground rod)?

Does anyone have a website I can go to that spells out exactly how to do the cage? I get the galvanized trash can but how in the world would you ground it? If you put a cage in your basement, would you have to run a wire to the outside to ground it? Also, how would you know when it is safe to take the protected items out of the cage? Sorry...lots of questions, I am totally new at this.


I was researching EMP and stumbled on to your website. I am looking forward to exploring it more.
My question relates to EMP and cars. If you have an old car that doesn't have any electronic ignition or any solid state parts would it still fry? I am assuming that it is just parked on street with no special grounding. It sounds like the article is saying yes.

the end of the 60's is when so many of the vehicles started adding more electronics. And yes, your assumption is correct. You may want to keep a spare car battery in a Faraday cage though to protect it.

To get a proper Ground the best thing to use is a copper ground wire attached to copper rod 9 feet long pounded into the ground and a 12 inch hole around the ground rod filled with water. Ok that's the military optimum for grounding. Yes they do worry about EMP.
Look around your home close to your power box. There could be an exposed piece of metal that has many wires affixed to it. that is your "ground or lightning rod".
Now for some Field expedient forms of grounding. Now these Ideas are not guaranteed but they did work for us in the Army.
1.Never have a loop in any of your cords, signal or power.
2.Always make sure you use bare metal to bare metal. Don't allow rust,or paint.
3.Just like you give someone a jump on a battery always make sure one connector is grounded.
4.In Iraq when on the move we always had a wire connected to the ground point and if we could not bury a ground rod we drove over it and then soaked the rod in water.
5.Sewer pipes and Fence Posts
If you don't have time and you do get some warning these make pretty good grounding rods.

If you have time to add it to your water, salt is great to make water more conductive.

So how do you know when you can take your stuff out of the faraday cage? Does the flare only last a few seconds and then everything is fried? Is there some residual that you have to worry about?

The chances of one EMP being followed by another afterwards is VERY remote. EMP's are a cheaper way to attack, but they ARE still a nuclear bomb. So yes, if it's an EMP that has caused your power outage, then you should be fine after its impact. If it's a solar flare storm, it's anybody's guess.
No, there's no residual otherwise.

Just to follow up on some additional research.
1.There is a lot of bad info on the net!
2.I went back through the US Army's EMP standards and the scariest thing I found is the Army is not sure if what they are doing for EMP will work!
3. Some things that all seemed agreed on is...
Metal must be at least 1mm thick and a good conductor.i.e copper is better than lead
Items must be insulated from your conducting metal. If your radio or batters are in direct contact with the metal the will be zapped.
Grounding seems to be a good idea but has not been proven to help or hinder.
I will be researching the US Navy next since the did all those Nuke tests at Bikini atoll.

http://www.scribd.com/doc/18518565/Effects-11 Gladstone report for DOD and DOE on EMP Johnston Atoll tests.
It seems that multiple layers of protection is the recommendation.
I will place my items in an ESD Bag. (I have a bunch of them leftover from building and upgrading PCs) Sealed with electrical tape, wrapped in heavy duty Foil and then placed in a Plastic bucket in a grounded metal trash can. Not sure if it will work but I think it will be the best I will be able to do without a full retro fit of my home.

If I build a Faraday Cage like the first picture above out of 2x4 frame and a mesh wire fabric, does the bottom have to be mesh too?

I want to build a box big enough to fit over my outside backup generator.

None of it has to be mesh, but solid copper plating will be more expensive.
If you use mesh, you have to use a very fine mesh so that the holes are not big enough to let in microwave-length radiation. For some idea as to the hole size, look at the door to your microwave at home. You'll notice a mesh that you look through to see the food inside while it is cooking.
What is most important is that whatever you are trying to protect is COMPLETELY enclosed (top, bottom, and all sides), that it is well-grounded, that whatever you are storing inside is insulated from the exterior mesh, and that there are no wires linking something inside with anything outside.
In other words, you could store your generator in a faraday cage, but to use it would require you to open the faraday cage in order to plug it in, etc.
Hopefully that makes sense. Good luck with your project.

I purchased a small galvanized can to use as a Faraday box. The problem is that, with the lid securely clamped down and no gaps whatsoever, radio signals can still get through. I tested this with both my cell phone and GMRS hand-held radios.

What did work? Wrapping the devices in aluminum foil - could not call the phone, keying one radio did not reach the other.

Question; what about mesh made of metals other than copper?

Was it grounded properly?
Were the contents insulated from the galvanized can itself?
There are a lot of variables that go into creating a working Faraday cage.
Also, it isn't radio frequencies that you have to worry about from an EMP.
The problem with an EMP is the ions that travel at high-speeds, thus creating great power, which will destroy diode substrate layers, thus causing electronics to stop functioning.
So, the fact that you can or can not stop radio waves from getting in is not an indicator of whether or not it will work as a Faraday cage.

In regard to 1968 automobiles... most cars built prior to then used DC generators and were a positive ground system versus the alternator and negative ground used in post '67 models. The alternator, by definition, produces an AC current which is rectified to DC though a diode network and then regulated by a zener diode designed to conduct at 14.4 volts DC with the remainder of the voltage dropped over a fixed resistor. In the event of an EMP, the battery, alternator and regulator would become useless so replacements should be kept in a safe environment. I hope this helps.

How should you protect a post 1960's car? Could you build a faraday cage for it?
And are gas generators protected from an emp?

Yes, you could fit it with a Faraday Cage. You will need to protect anything that has electronic diodes and transistors--usually something found in gas generators.

I liked someone's comment about the metal filing cabinet.....would that work and how do you ground something inside your home? Thanks

You'll need to ground it and the metal has to be a continuous connection throughout. So it's a good start, just a couple of physics issues to work out.

Even if you put your Generator in a Faraday cage to protect it, where would you get gas to run it?..gas pumps wont be working...

While reading this article, I was curious as to your background in which made you such and expert. Then I came across "The higher the frequency of the magnetic pulse, the faster it is." which is total BS and confirmed my suspicion that you have no idea what you're talking about. All EMR travels at the speed of light "C". It is COMPLETELY independent of frequency. "C" varies a bit based on the medium is traveling though, but that's it. And Faraday cages don't need to be grounded, just ask AirForce One. Also, your mesh will do fine if it's and EMP generated by a solar flare which is solely E3, but it will not stop the tiny wavelengths of the E1's gamma rays.

While I suspect you had no intention of actually learning something when you posted your uncouth comment, I'm still going to be kind enough to address your issues so that others may avoid being misled by them. I'll do my best to answer though I'm afraid that some of your grammar and typos may leave me with some confusion in this endeavor.

First and foremost, keep in mind we're talking about an EMP here. It seems your accusations are based without that clear distinction.

When it comes to an EMP, electro magnetic pulse--most folks forget that there are EMP frequencies that are WELL BELOW the speed of light, but an EMP that's sufficient to do major damage will be at their max. frequency. In other words, it's a mistake to assume that there's no such thing as an electro magnetic pulse frequency below the speed of light. As an example, there's an EMP every time your spark plug fires, but it's certainly not going to be harmful to other electronics. Radio frequencies are an EMP.
Unless your equipment is hardened against DAMAGING EMP frequencies and unless you know the compacitants value of the insulation layer in the faraday cage is greater than the capacitance value of the cage to the ground, then you run the risk of damage to the equipment--even if it's inside the Faraday cage. The solution to such a problem would be to GROUND the faraday cage.

Erego, you're mistaken when you state that an EMP generated by a solar flare is solely E3 and your understanding of E1's, etc. The question is how fine is the mesh? Chicken coop mesh won't stop anything that has enough power to wipe out every diode on the earth. Also, contrary to what you might see on YouTube, just because a mesh stops radio signals or the low signals which cause a cell phone to ring, does NOT mean that it will stop solar flare E3 values.

High frequency is tiny wavelengths and the E1 gamma rays are tiny wavelengths, just b/c u prepare for solar flare e3 doesn't mean you've prepared for nuclear produced emp.

A lot of this is speculation, and much of the time it may be unnoticeable, but with
the right GPS you can check out what times will be best to be in the field.
Likewise, for factories, radio communications are being used to
communicate over a wide area which saves time and money.
The use of this type of a radio can be traced back to the use of
transmitters and receivers that were used
to exchange messages wirelessly.


I live in an apt. I would like to protect important items such as PVS-14s, IR lasers, Commo, Solar panels and inverters, deep cycle batteries, ect. If I build a cage large enough (6ftX2ftX3ft)
How would I effectively ground it? Would plugging it in to the ground of an electric outlet suffice? Also, if i were to build a smaller cage to put inside my truck for when I travel,
how would I ground that?

The ground prong in an outlet

The ground prong in an outlet is better than nothing, but if you have access to a metal water pipe, ground it to that instead. Vehicles are not grounded. They are insulated from ground by their tires. So there is nothing in a vehicle to ground it to.

I would like to offer some

I would like to offer some information based on my experience in the GPS, Communications and RF design field. Some of this work was for aviation and the military. Often I worked inside of a "Screen room" (Faraday cage) when developing and testing rf systems. It was not grounded and would make no difference if it were (tried it). They work by rearranging charges on the surface of the cage. The charge on the inside surface of the cage is zero. No need to insulate the inside. Also, all Faraday cages are frequency dependent. the may work well at 10khz, but poorly at 1 Ghz. They are designed out of a variety of materials specified to provide effective shielding at the desired range of frequencies and types of electromagnetic and magnetic fields. Additionally, I followed many of the designs through a barrage of environmental testing including resilience to large (similar to the E1 and E2 HEMP components) and rapidly changing electromagnetic fields. Antennas, power lines, and all wires that pierce the shielding do couple energy inside. It does make a difference. The article may be somewhat broad to comment in the absolute. Not trying to start a conflict, just share my knowledge and experience.

Best regards,


P.S. You have a great site...Keep up the good work!

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