The Many Myths of EMPs and Faraday Cages

EMP Myths and Faraday Cages--by Guest Contributor Scott Bishop

EMP Myths and Faraday Cages We talk about EMPs and Faraday cages periodically on here as well as our Facebook page and it seems that every time we do, we discover a LOT of misconceptions about the two. There’s no shortage of completely bogus and illogical YouTube videos published on the topic—even by those claiming to be engineers or PhD holders. Unfortunately, far too many are buying into such nonsense at the risk of losing a critical asset amidst a crisis. So, I begged and bribed my brainiac sweetheart to write an article for our readers and specifically address the most common misconceptions that people have about EMPs and Faraday cages. As you can see, he gave in to my bribing. *grin*

Here it is. (Thanks, Honey!)

The basics of an EMP

An Electro-Magnetic Pulse (EMP for short) is a short and powerful burst of electro-magnetic energy. This phenomenon occurs whenever an electro-magnetic wave occurs forcefully and suddenly. This can happen in a number of ways. For instance, an EMP attends each and every lightning strike, albeit on an extremely small scale. This type of EMP, though common, is of little concern, however, because the amount of energy is relatively small and is spread out over a large amount of time (relatively speaking). This is important to understand when discussing the myths surrounding EMPs that may cause widespread damage.


EMPs occur throughout the nation, on a daily basis. Why aren’t we concerned about them? Because, generally speaking, they are limited in their effect, not being forceful enough, or not occurring in a short enough burst for any real damage to occur.


The EMP that is of concern though is one which is powerful enough to affect a wide area and which occurs in a short enough burst that it excites electrons in the stratosphere to the point that they will be thrust downward rapidly, generating a large amount of current. This generally occurs only in two situations, one being caused by nature, and the other being man-made, but both having similar effects.


Nature-made EMPs

Our sun, as wonderful as it is, is an EMP generator. We are constantly and consistently bombarded with EMPs from the sun, yet most are not powerful enough to have any real effect, let alone a lasting one. Sun-made EMPs (more popularly known as solar flares or coronal mass ejections) are brought about as explosions occur on the surface of the sun, which propels electro-magnetic energy outward. Once in a while, these explosions occur at just the right moment and in just the right place on the surface of the sun that when they travel directly outward from the sun, they directly impact the earth. When these explosions, and the resulting waves of electro-magnetic energy they cause are strong enough, they can damage electronics, knocking out communications, causing computer crashes, etc. This type of effect occurred during a solar storm in 1859, known as the Carrington Event, which damaged telegraph systems across the nation, and caused telegraph wires to catch on fire.


Above the stratosphere, the effects of a sun-made EMP are of fairly limited effect, both in scope and duration. This is because the EMP at that stage is nothing more than electro-magnetic force, in the form of high-powered high-frequencies. This has the effect of raising the noise floor of any electronic circuit within range of the EMP, causing modulator, demodulator, and other electronic circuits (built from transistors, diodes, etc.) to not be able to distinguish between the two levels of voltage they were designed for. This is called circuit overloading, and is usually temporary, existing only for the duration of the EMP and a short time after, as computer circuits reboot. (A similar effect can be seen on your car radio when one radio station begins to “walk” all over another radio station of the same or similar frequency.)


The larger problem occurs as those high-powered high-frequencies smash into the stratosphere, causing electrons to be propelled downward toward earth, which creates a large amount of current. It is these electrons, and the attending current, which cause damage to electronic circuits by shattering diode junctions (transistors are essentially two diode junctions, and electronic circuits include transistors and diodes). Of course, this only occurs when enough force is applied by the solar flare to begin with.


Man-made EMPs

Man-made EMPs can be categorized both as local and regional, as well as high-altitude and low-altitude.

Local man-made EMPs are of the variety being tested and used by both military and police forces, in the form of mobile EMP-generators. These emit electro-magnetic waves, and are directed at a specific target, such as a speeding car. Because this variety produces only an electro-magnetic wave, its effect is only that of circuit-overloading, and the electronic circuits will survive to live another day, though they’ll be off-line for a period of time.

Regional man-made EMPs are the truly scary variety that most people are concerned about. The only real executable application of this type is the HEMP (High-altitude EMP), which occurs when a nuclear device is detonated at, or slightly above, the stratosphere. The photons generated by this nuclear explosion travel down through the stratosphere, having the same effect as a high-powered solar flare, but with much higher power (being generated closer to earth). The current generated by an HEMP is high enough to damage any unprotected diode junction within line of sight of the HEMP. Because it relies to a great extent upon line-of-sight, it would take 2-3 HEMPs to cover the continental United States.


Let’s dispel some Myths about EMPs and Faraday Cages

  • “Foil and other like resources can protect electronics from EMPs/solar flare damage. I know! I saw it on Youtube!”

Not likely! There is a big difference between relatively low-power radio frequencies and high-power high-frequency EMPs. Foil may be enough to stop radio frequencies from getting through, but it is not substantial enough to handle the current generated by an EMP. Using foil to guard against an EMP would be similar to using 24 gauge wire for a car battery; it is likely to burn through. The Carrington Event of 1859 proved this point when it caused telegraph wires much thicker than foil to catch fire.

  • “Batteries will be destroyed due to an EMP”

Not likely! Most batteries do not contain a diode junction. The diode junction is the electronic part most likely to be damaged by an EMP. Batteries are made of relatively thick plates of metal, very dissimilar to the very small, narrow junctions used to create diode junctions. If anything, the short, yet powerful, pulse of an EMP may actually cause an extra charge to your battery, not that it will be that noticeable, since all of the electronics you run off of that battery will likely be fried.

  • “A person’s vicinity to an EMP doesn’t make any difference.”

Untrue! Just as light operates within the bounds of the physics, Law of Squares, so does electro-magnetic current. The further you are from the electro-magnetic field generator, the less of an affect it will have on you (or more specifically on your circuits). Close, line-of-sight objects will be the most susceptible to an EMP, while objects hidden behind mountains, or underground, will be much less affected.

  • “A car is already protected against an EMP, and it won’t stop driving in its tracks because of one.”

Pre 1967 cars vs EMP damage Untrue! Unless you are one of the few lucky enough to own a car not controlled by a computer of some sort (think pre-1967), your car is likely to be affected by an EMP which covers your area. Cars, like so many other things in today’s society, are controlled by computer, which is made of millions of tiny diode junctions (see discussion above). Even if you’re lucky enough to have your car underground when the lights go out, don’t plan on having much gas to put in your car as the computer-controlled pumps are likely to be out of commission.

  • “Planes will fall out of the sky when an EMP hits.”

Not likely! Though the electronic circuits, which make planes so much easier to control, will likely be damaged beyond repair, planes operate on the basic principles of lift and thrust. Though they will likely be turned into permanent one-time-use gliders, planes will not be forced down just because their engine controls have become useless pieces of waste; though I wouldn’t want to be one of the many pilots trying to find a field big enough to call a landing space for a 777, and particularly not without any ground lights for guidance or reference if an EMP event should happen at night.


What other EMP myths or mysteries have you heard that you’d like our take on?  We’ll address them in future articles.



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Just want to say thank you ..

Just want to say thank you .... first comprehensive explanation I have read on EMPs...... Thanks again...


you comment that Batteries should be ok, but in your post( EMP 101: Part IV—Faraday Cages) you state batteries will short out ?


This clarifies WHICH

Preparedness Pro's picture

This clarifies WHICH batteries can short out.

Loved the article!! Any

Loved the article!! Any thoughts on how an emp might affect those with pacemakers or defibrillators?

Very informative article.

Very informative article. This explains a lot to me. How would an EMP affect refrigerators and other appliance, even mixers and the like?

Excellent article and great

Excellent article and great follow up links to help folks learn more and be able to take steps to mitigate EMP. Thanks I will pass this along. Cheers, EvS

Dec 24th 2012, my heart

Dec 24th 2012, my heart stopped. Everyone wanted to install a Pace Maker and Defibrillator combo. I asked about the EMP and we decided I did not need all the electronics in my chest.
Found out meds I was being given did not play very well together.
Doing fine.

Very informative looking

Very informative looking forward to more on the subject. How can we prepare? We live in NW MT.

Some very good clarifications

Some very good clarifications in your article. But as in most articles about EMPs I didn't find much that will actually help me save any electronics should some rogue country go nuclear above the USA. Okay, tin foil won't work. Thanks for debunking that one, but now I have to find another method to protect my walkie talkies. Any suggestions other than just "Build a Faraday cage"? How does one go about doing that?

This is an article that was

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This is an article that was already quite lengthy.  There's only so much one can cover in one article. Subsequent education is coming.

OK I understand that you don

OK I understand that you don't think aluminum foil will protect during an EMP event. So please tell us what type and thickness of shielding you do believe is necessary to protect equipment and devices. I have read where some electrical engineers have used 55 gallon metal drums. How about metal office cabinets or metal filing cabinets. I currently store my electronics in a large metal filing cabinet with rubber and cardboard between the metal shielding and my devices.

The file cabinets won't work

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The file cabinets won't work because there are far too many gaps. The 55 gallon drums would still need to be grounded, but otherwise would work so long as there are no breaks in the metal connection.

Why do gaps matter? I just

Why do gaps matter? I just went to the lightening show at the Boston museum of science and there was an engineer literally standing in what looked like a bird cage while it was struck hundreds of times by millions of volts from a van der graph generator. He actually was touching the cage on the inside exactly where the lightening was striking. He said all the electromagnetic force travels on the outside of the cage. Some dependable answers on this subject would be great is there a book available?

You're misunderstanding "gaps

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You're misunderstanding "gaps" vs "holes". The Birdcage style doesn't have any gaps. In other words, the grounded metal is continuously touching. There's nowhere for the surge to jump. There's contact all the way around. If there's somewhere for the surge to jump, then it's not a proper Faraday cage and you'll lose any protection.

So I wonder if a ground strap

So I wonder if a ground strap to the lid on a metal garbage can in addition to grounding the can would work

If there is a gap between the

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If there is a gap between the lid and the garbage can, you'll lose all effectiveness. You've got to make sure that the surge can flow from the lid to the base of the can. just remember that and you'll be fine.

All metal garbage can with a

All metal garbage can with a lid lined with cardboard is that fine for stashing electronics? Do you subscribe to Space weather news updates which offer solar flare actions, among other events.?

I have a Myth I would like

I have a Myth I would like Busted so to speak, I have seen and laughed at so many people saying they can turn a 20.00 Metal Trash Can or an Old Dead Microwave into a Faraday Cage to house their expensive electronics. Though, Wouldn't that mean leaving your laptop and Ipad in there all the time since you never know when one will happen...

if the trash can doesn't have

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if the trash can doesn't have any interruption in the connection AND if it's properly grounded, then it will work. Same as the microwave. BUT... you're correct. The person would have to have a "back up" computer, ipad, etc. in the Faraday cage at the time of the EMP or Solar Flare in order for it to be protected. ;-)

Could you please offer more

Could you please offer more resources on this issue? Perhaps the EMP commission report that showed most vehicles would continue running?

This isn't the only article

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This isn't the only article written on this topic. And since this is a blog as opposed to a book, we try to keep the articles shorter than an exhaustive on any given topic. All one needs to do is to put in a search for "EMP" or Faraday Cage in the search bar and more articles will come up on this topic. One can also do a internet search on the EMP commission report that you're referring to, which was presented just before 9/11 took place. Hope that helps.

I took a cookie tin an using

I took a cookie tin an using the rare earth magnets from a old hard drive with a small bungee cord strapped it to my gun safe electronic keypad as a Faraday cage. This set up while crude is easy to remove and should protect the electronics from an EMP event. Your thoughts would be appreciated.

No, this is not an acceptable

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No, this is not an acceptable Faraday cage. You have GAPS between the metal. There's no continuous flow of metal and you're lacking the grounding as well.

Most cars are resistant to

Most cars are resistant to EMP. In the early 1990s Jaycor had a research program to employ EMP to stop cars - like an electronic spike strip. It never worked, unless physical contact with the vehicle could be made. It's true todays cars have many more computers - but most of those don't affect the engine or transmission. So after an EMP, they will likely drive, but you won't be streaming music via Bluetooth.

Sorry, but I'm calling BS on

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Sorry, but I'm calling BS on this. It's simply NOT accurate. If a car runs on power steering, power brakes, etc. then the car will most definitely fail to operate properly in an EMP scenario. Also there has NEVER been an appropriately synthesized "EMP experiment" that carried the same amount of weight as a real solar flare or nuclear EMP event would. The US Military attempted to do so--once--only to end up shutting down the electricity in a wide multi-block radius.

>> If a car runs on power

>> If a car runs on power steering, power brakes, etc. then the car will most definitely fail to operate properly in an EMP scenario

I feel it's important to point out what may have been a hastily made statement that could be misunderstood...

Almost every car on the road today uses hydraulic braking and a mechanical steering linkage. There may be electronic doodads like ABS, power assist, etc. - but the main functionality is old school. It won't be as pleasant to drive without those assists, but it's also far from impossible.

Possible exceptions: there are a growing number of cars with "steer by wire" or "brake by wire" systems. Depending upon the details, those seem likely to fail catastrophically without computer control. But I really don't know enough about them to make an educated guess.

As has been described, the hard part will be keeping the engine running without an ECU. But the car will not be uncontrollable. Don't believe me? *carefully* shut off your engine while moving and see for yourself.

Not to mention the solenoid,

Not to mention the solenoid, responsible for starting the car in the first place. When that gets fried, you're SOL unless you've got a spare. This is true of all vehicles, even those from before '67 or whenever, which is why some owners of said vehicles keep a spare one in a Faraday cage (whether the cage works is another matter).

It is also wise to have spare

It is also wise to have spare high voltage coils they are more likey to be damaged. Also do not forget points and a condenser which may also be melted due to arcing. Possibly spark plugs too, depending on strength of the EMP.

Very interesting information.

Very interesting information. For us non technical peeps, is there a place we can buy faraday cages (because we just aren't adept enough to build one ourselves) to store our radios, phones, walkie talkie etc....??

Can a whole house Surge

Can a whole house Surge Protector help with an EMP blast? Just wondering.



Do the effects change when

Do the effects change when the devices are unpowered and with out an electrical source?(ie batteries)

Nope...whether an item is in

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Nope...whether an item is in use or not at the time of the impact, it won't protect it from being destroyed.

It's going to rely on the

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It's going to rely on the system you use. The solar panels themselves won't be harmed necessarily, but the parts that connect to the panels to bring the power to the home are parts you'll want to have duplicates of.

I was working a few years ago

I was working a few years ago in the winter and my old 1998 Chevy van wouldn't start. I had to stay overnight while a dealer tried to fix it. At first he thought it was a fuel pump. but it turned out to be a bad computer.

The dummies at GM mounted the thing unprotected on the firewall and salt ate the thing up. Moral: A car won't start if the computer is toast.

If it is "line of sight" then

If it is "line of sight" then do you need something UNDER a home generator as well as all around it? Do you recommend any easily purchased material to make a large (or small) Faraday blanket?

While line of sight helps to

While line of sight helps to explain the propogation of EMP, it should only be considered such for large areas dividing from other large areas. A Faraday shield must fully enclose and be grounded. Without a full enclosure voltages will still be induced and propagated to items that you may wish to protect. There is no such thing as a faraday blanket.

Faraday cages don't protect

Faraday cages don't protect from solar flares. Flares are the E3 pulse (fry power lines, etc.) while the cages protect from nuclear EMP E1 pulses. Not sure why you didn't publish my previous comment on this.

I ask the factory Rep for my

I ask the factory Rep for my pacemaker if my pacemaker would be destroyed in the event of a EMP and he told me that it would be destroyed by a strong EMP and because I am dependent upon the pacemaker I would probably pass away.
Now concerning Faraday Cages. I am an old man and many years ago, i was told that a faraday cage had to be "grounded"in order to work, that is, the metal around the object you are trying to protect has to be grounded and that makes sense to me. The EMP is a electromagnetic pulse and grounding the faraday cage would send the pulse to ground somewhat like a grounded lightening rod sends a lightening bolt to ground. However, I notice now in many writings about shielding your radios etc from a EMP that there is no mention of grounding the metal you place around the radio etc. as a Faraday Cage to protect it. Does anyone know if the Faraday cage truly needs to be grounded to work? If it does, then people had better be made aware of that.

Yes, it does need to be

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Yes, it does need to be grounded in order to work. I keep reminding people of this in EVERY Faraday cage or EMP related article.

Good Analysis-

Good Analysis-
Just one flag on the play.. I agree with you that most vehicles will be in an uncontrolled state, causing numerous fatalities.

The same applies to modern aircraft which are now mostly fly-by-wire with no mechanical backups. The factor of safety in their design lies in the fact that these systems are triple redundant. The DC9 had manual reversion and cable controls, but the 757, 767, 777, 787, and all Airbus models as well as other makes have no way to control the aircraft if all flight control computers fail. Most FADECs (engine controller) will fail to a reduced power setting, but the flight controls would likely fail completely.

As of this minute there are 10,000 aircraft being tracked in CONUS by FlightAware. That's approximately 2 million passengers aloft. At say a 90% mortality rate, that's 1.8M casualties within the first few minutes of a HEMP attack, plus ground casualties. Not good to be on an airplane.

Beyond that, USG estimates 90% US casualties within 365 days.


Actually large aircraft are

Actually large aircraft are no longer cable controlled, the wings are controlled via computer the controllers in the cockpit. In the event of power failure, there are back up batteries, but I'm skeptical of the failsafes being able to power up after an EMP. Especially if it's one powerful enough to disable vehicles and "burn telegraph wire."

For the record, it was the insulation that caught fire from the surge which was picked up from the exposed bits where the wire was hung - not the CME getting through the insulation itself nor the conductor itself catching fire.

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