Preparing for an EMP Attack – Can Faraday Cages Help?

faraday cages

An electromagnetic pulse, or EMP, may sound harmless enough but its effects can be devastating.

An EMP is essentially an intense burst of energy (for instance a lightning bolt, which is simply a highly concentrated EMP event that is very localized) that, depending on size and intensity, could potentially wipe out electrical and information systems across vast areas.

EMPs can occur naturally, as with lightning and a case we will explore later in this article, as well as through man-made sources such as nuclear or radio-frequency (non-nuclear) weapons. In order to properly prepare for such a phenomenon – whether to defend against Mother Nature or technological warfare – it is imperative to have a clear understanding of what exactly an EMP is in order to properly prepare yourself to defend against it.

faraday cages
Modern day reliance on the power grid leads many preppers to classify EMPs as a serious threat.

The following article will teach you the basics in understanding what an EMP is, how it can be caused, and the short and long term effects. This article also explores Faraday cages and how they can work to protect you against EMPs, discussing the features that are most important and various types you can purchase and build yourself.

What is an EMP and How is it Caused?

An EMP – whether natural or man-made – is a burst of energy with the power to knock out electrical power. The lasting effects of an EMP can range from minor inconvenience to potentially sending the world back to a pre-communications technology ‘dark age,’ so to speak.

Man-Made EMPs

The largest man-made EMP threat looms from nuclear weapon detonation. In what is referred to as the Compton effect (named after physicist Arthur Compton who first theorized of the effect), the theory follows that when a nuclear bomb explodes, the explosion releases electromagnetic energy which binds to molecules in the atmosphere and releases bonded electrons.

These free electrons then interact with Earth’s natural magnetic field creating a current that is powerful enough to decimate electrical currents over a large expanse of area.

faraday cages
As devastating as a nuclear explosion is, the resulting EMP can reach even further than the physical destruction of the blast.

In 1997, Gary Smith, then the director of Applied Physics Lab at John Hopkins University, testified in front of the House National Security Committee that a nuclear detonation at 300 miles above the surface of the Earth could carry enough impact to knock out electrical power to the United States as well as most of Canada and Mexico (click here for source article).

faraday cages
Lights out across the continental U.S.? A disturbing prospect.

However, nuclear weapons are not the only ones capable of generating an EMP; more localized sources of energy such as radio-frequency weapons or non-nuclear EMP devices can also wreak havoc.

Instead of drawing energy from a bomb explosion, these devices use concentrated microwave energy to cause disruptions in electronic equipment and destroy data. While these devices deliver a non-lethal pulse, the damage to electrical systems is no less devastating than with a nuclear detonation.

Naturally Occurring EMPs

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The energy of lightning bolts is concentrated and terminates when it strikes the ground.

In addition to lightning, EMPs can also occur naturally as a result of geomagnetic storms. While these occurrences are infrequent, a geomagnetic storm in 1921 affected the United States as well as parts of Europe for two days, closing the New York City railroad system and burning telegraph lines in Sweden.

The cause was later attributed to a group of sunspots that were 1.9 billion square miles in size. Today, a storm of this size would affect over 100 million people and cause widespread panic and chaos due to society’s heavy reliance on electronic devices for everyday life.

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Geomagnetic storms can produce an aurora borealis effect, or “northern lights.”

Despite the increased vulnerabilities present in modern times due to the prevalence of electronic devices in managing day-to-day activities, a future natural EMP event will likely come with advanced warning thanks to the benefit of space-monitoring stations.

A solar event would take hours, or even days, to reach Earth’s atmosphere, providing enough warning to safely stow electronics and turn off power systems (while shutting down power will not completely immunize systems against damage, it certainly can reduce the risk).

EMP Damage

EMPs, regardless the source, have the potential to inflict immediate and long-term damage. Depending on the intensity of the pulse, EMPs can start electrical fires, incapacitate power grids, and shut down power sources for refrigeration (causing loss of food and medical supplies), water and sewage services, security systems, and phone and Internet (this would affect financial institutions and ATMs as well as land, sea and air transportation).

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Daily productivity would come to halt for many people in the aftermath of an EMP.

Additionally, any cars relying on high-tech computer systems (basically any model manufactured in the last 20 years) would be disabled and back-up generators could experience malfunctions or be ineffective if the existing equipment is damaged.

Recovery from an EMP is dependent on the size of the affected area and location, but could potentially take many years.

What is a Faraday Cage and Can it Protect Against EMPs?

The good news is, you can protect your electronic equipment from an EMP event. A popular method of EMP-proofing is to use a Faraday cage, a protective container equipped with a conductive outer layer that is typically made from aluminum.

A popular method of EMP-proofing is to use a Faraday cage, a protective container equipped with a conductive outer layer that is typically made from aluminum.

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Simulators can be used to test the effectiveness of Faraday cages in diverting incoming energy.

These containers function as a shield, protecting the electronic devices inside from EMPs. The term ‘cage’ originates from the fine metal mesh often used as a protective wall; however, research indicates that using a solid sheet of metal may be more effective (more on building your own faraday cage later on).

A Faraday cage can be built to any size to accommodate myriad manner of objects; keep in mind that an EMP can cause a voltage spike powerful enough to fry all manner of electronic devices, including cell phones, computers, radios, and appliances. The only must-have in constructing a Faraday cage is that it needs to be thoroughly lined by a conductive material with no gaps.

faraday cages

How Does a Faraday Cage Work?

The manner in which a Faraday cage can protect against an EMP is by using the conductive layer to diffuse energy rays (this is why it is imperative to have no openings through which energy waves can pass). The process is referred to as field cancellation, with ions in the conductive material realigning themselves to cancel the incoming electric field.

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The energy flows along the surface rather than through the cage. Image via Britt Selvitelle on Flickr.

How Can You Test If Your Faraday Cages Works?

There is a very simple way to test the effectiveness of a Faraday cage: place a working cell phone in the cage and try calling it. A properly functioning Faraday cage will block the signal and the call will not go through.

How To Build a Faraday Cage

The best way to prepare yourself and your loved ones for an EMP is to prepare for the aftermath by ensuring you have adequate stockpiles of food, water, and other essentials. In the event of widespread electricity loss, store shelves will quickly empty and essential resources will become scarce.

Not only will having the supplies ready beforehand ensure you have enough to last, but also, in a worst-case scenario, there may be civil unrest or upheaval that makes it dangerous or impossible for you to leave your home, necessitating having sufficient supplies on hand. CLICK HERE to read The Bug Out Bag Guide’s comprehensive article on prepping for power grid failure.

power grid failure

In addition to preparing for the aftermath, having a Faraday cage built and ready to go is a measure you may choose to take to protect your household devices in the case of an EMP.

Homemade Faraday Cages for Large Devices

To protect your larger devices – including computers, televisions, tablets and appliances – a large ‘shield room’ can be fashioned by lining a closet with heavy-duty aluminum foil. When constructing your shield room, be sure to pay careful attention to how your foil is placed around the door frame so that it provides a continuous shield.

Laying a piece of cardboard on the floor as you load items into the closet can help prevent damaging the foil. Additionally, check for any outlets in the closet and ensure nothing is plugged into them and that they are also covered with foil.


If you don’t have a closet ready to go, or are prepping a location that is not in a home, you can build a freestanding Faraday cage by framing a box with 2x4s and then lining the outside with fine, conductive mesh. Remember, the openings on the mesh must be small enough to prevent energy waves from entering.

In place of mesh, you can also use sheets of aluminum or copper for your shielding material. Whatever material you choose, ensure its coverage is continuous over the entire exterior of your cage, or else its shielding effects will be rendered useless.

Homemade Faraday Cages for Small Devices

For smaller devices, something as simple as a shoe box lined with heavy-duty aluminum foil can do the trick. Alternatively, you can wrap your devices in several layers of foil, which also functions as an effective means of protection.

If you are considering building your own Faraday cage, make sure to check out this article and other resources with detailed building instructions.

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Cell phones are very susceptible to the burst of energy from an EMP event.

Purchasing a Faraday Cage

You may already have a store bought Faraday cage ready to go and not even be aware of it – your microwave oven. While most people are familiar with their microwave’s ability to keep radiation in, few are aware that a microwave can also keep radiation out. To test your microwave’s effectiveness, unplug it (this is an essential first step, do NOT attempt this exercise while the microwave is plugged in) and run the cell phone test discussed in the previous section, How Can the Efficacy of Faraday Cages Be Tested?

There are also anti-static bags, available in a variety of sizes, that can protect against electrostatic discharge and are easy to store in your get home bag.

Protective ContainersBest For
Faraday Cage EMP/ESD Bags - 10 count
Cell phones
USB memory sticks
GPS devices
Protektive Pak PPK-27534 5 Piece Storage Container and Lid Set
Cell phones
USB memory sticks
GPS devices
Tech Protect Faraday/EMP Bag Size XXL 32" x 38"
LCD monitors
Towers/hard drives

How Effective are Faraday Cages?

The effectiveness of your Faraday cage in protecting your devices against an EMP is dependent on a number of factors, including the origin of the EMP, how far your Faraday cage is from the EMP, and the type of rays emitted by the EMP.

High-frequency waves require smaller holes in the meshing while short-range EMPs contain gamma rays and X-rays that cannot be blocked by only a single layer of heavy-duty foil. To fully protect against EMPs from radiofrequency weapons, thick sheets of metal are required.

What You Need to Know About EMPs and Faraday Cages

In today’s technology-enabled world, it is easy to imagine the devastating consequences that could arise from a prolonged loss of power. A larger EMP that destroys power for several weeks, or even months, could easily lead to civil unrest and throw many first world residents into a survival situation.

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The effects of a solar storm may take up to a day to reach Earth.

While Faraday cages provide an effective means of first-line defense against EMPs, remember there may be little to no warning before a strike and you may not have the opportunity to put your Faraday cage to use. The best way to prepare for an EMP event is to prep yourself and your family for the aftermath, ensuring your stockpile of supplies will be adequate to see you through a potentially long-term spell of power-free living.

Further Reading

Your Thoughts?

Are you fully prepared in the event of power grid failure? What must-have items have you stored away in case of power failure? Are Faraday cages part of your overall prepping strategy? Do you know of any other means to protect against EMPs? Share your thoughts in the Comments section below, thanks!


Chris Ruiz

My name is Chris and I created this site to help ordinary people prepare for the uncertainties of the modern day world. I believe that a well-prepared society is the best safeguard against any natural or manmade disaster.

14 comments on “Preparing for an EMP Attack – Can Faraday Cages Help?

  1. You said: “The only must-have in constructing a Faraday cage is that it needs to be thoroughly lined by a conductive material with no gaps.”

    How must have is this? If a pinprick size hole is in the foil or copper sheeting, or whatever, does that completely reduce the effectiveness of the cage? Does the adage “some is better than none” apply to a Faraday cage? If I have nearly the entire internal surface of a closet lined appropriately, but a small crack on the edge of the door is missed, will the strength of the EMP be reduced?

    1. Hey Garth, Good question!

      For solar flares or lightning, the waves lengths are on the order of 100s of meters, so a small pin prick would not allow the energy waves to enter. Nuclear EMPs have wavelengths as short as several inches and Non-nuclear EMP devices as short as a few centimeters. For these, a continuous surface is recommended, rather than a mesh screen. If using heavy duty foil, you can add a second or even a third layer to protect against accidental openings and maintain a continuous conductive surface. Also, the energy that can enter the hole will be proportional to the size of the hole, so keeping your electronics a distance away from the sides is a good precaution.

      Good luck prepping!


      1. Chris,
        I’m building a garden shed, can I use metal window screen as a CME shield To encapsulate the shed? Just looking for something that is more robust than aluminum foil and still be cost effective.

  2. Faraday cage will be out of date for new generation of e bombs.
    the good news its still possible to protect devices from pulse but the bad news it is in back end designing of devices and architecture of them so it’s not possible by users and people.
    it may we have “E pulse protected” as an option in many devices after world war3.

  3. I was planning to add insulated aluminum siding to my steel roofed home and a chicken wire screen under the floor in the crawlspace to form my Faraday Cage. Do I also need to cover all windows outside with either chicken wire or inside with steel roll shutters?
    What is the best way to connect the siding to the under floor chicken wire mesh and how many connection contacts need to be made between the aluminum siding and the steel roof?

    I use an old radar range in my shed for a back-up laptop, DVD player, USB drives, and radio.

  4. How exactly are you going to call anyone even if your phone survives ?
    Are you just gonna play angry birds until your battery dies? Same with flashlights and batteries etc. Shortwave radio is only thing worth protecting. But you’ll need power to sit and listen for a few months or even years so batteries won’t cut it. Most all generators now have electronic chips etc so that won’t work either.

    Don’t forget that radiation is everywhere and total devastation of environment so you won’t be eating or breathing any air either. Pretty fucked up if you ask me.

    As Oppenheimer said the living will envy the dead.

    Best to not count on electronics if nuclear war starts.

    1. You are right, I wouldn’t count on electronica devices. However, it would be foolish to just discard protection of them. It’s possible that not every communication outlet will be down … and if so there may be power for them in the future. And if you are lucky enough to have survived, you’ll be incredibly lucky to have devices to communicate on with the outside world. Not protecting them is giving up on life before you ever have to.

      1. Small solar panels kept in the faraday cage could be effective also if you have an exercise bike that can relatively easily be rigged up to enable you to harness electricity from it.

        1. Solar panels in a Faraday cage would work but if it is a manmade attack they would probably hit you agian a month later just to get the prepped.Any thing that uses batteries would have to be recharged reguralry. Having a transmitter would probably alert the wrong people to your location.A reciver is the best idea.

  5. I think that there is also a danger for devices that have wires connected to for example charging or data connections. These wires that go outside the faraday cage can in fact pick up the EMP energy and direct it into your “protected” devices. So keep this in mind also when protecting devices.

    As for air and water quality, I agree, it is going to be very nasty indeed. While you may have shelters etc, you still have to come out eventually, and background levels will be elevated for years causing illnesses worldwide, not to mention nuclear winter for at least 2 years that will cause famines. Dealing with soil pollution will be a major challenge. Sad if we must go through this; 1959 total military spend = $500 million; 2019 total military spend = $700 billion; Swords to plowshares? dream on.

  6. So after the emp attack ends, will my iphone be any use if the internet destroyed? Will texting another iphone be possible?

    1. The Internet was designed so that if there is a localized attack the internet routes around it. But that wont be of any help to you if the explosion occurs in your local area as the Cell Phone masts will have been fried.

  7. Iphones and money will be in short supply after though…so you’re first in line to cell signals when towers are re-established in the area. A satphone may make more sense though. I think the most important thing to figure out would be protecting a generator and any equipment you need to sustain life (heat, air, food, etc depending on your location). Fuel will eventually run out but it gives you a small jump start on solving problems and protecting your family. Also, flash drives with important pictures/documentation or any guidebooks, etc that you weren’t able to get hard copies of.

  8. I used an old 4 or 5 drawer metal file cabinet. With wrapping items inside with foil. Batteries rotated every 2 years. LED light bulbs, LED flash lights, Solar powered radio, solar cell charger incase any of my solar panels survive. etc. IF the power comes on again you want least loads possible. Also my aluminum siding is grounded. SO about 3 layers not perfect but every layer helps eliminate direct route of the EMF to the circuit. From an Electrical Engineer. PS if there is any pre warning unplug everything as most appliance’s are metal encased. Breakers off. Pray it never happens.

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