How to Build a Simple Faraday Cage for EMP Survival

Of all of the reasons to prepare, one that we all need to take seriously is the possibility of a catastrophic EMP, or electromagnetic pulse. This is a frequent topic in many post-apocalyptic novels and something that most of us are aware of, even if we do not completely understand the science.

As I wrote way back when in the article Prepping for an EMP and Solar Flares:

To be blunt about it, an EMP, if large enough, would affect the entire planet.  In an instant, civilization as we know it would change as we get swept backward in time by a century or two.

Understanding the risks of an EMP goes hand in hand with threats of a cyber-attack since there is a cause and effect relationship between the two.  In this article I want to accomplish a few things:

Explain EMPs and the risks in simple, easy-to-understand language
Give you instructions to build a simple Faraday cage to protect your electronics
Provide a list of items to put inside your Faraday cage

What is an EMP?

An electromagnetic pulse or EMP, is an abrupt burst of electromagnetic radiation.

To start with, an EMP is caused by certain types of high energy explosions.  A nuclear explosion, for example, will surely cause an EMP.  Likewise, an EMP can be the result of a suddenly fluctuating magnetic field.  Or, as I have mentioned before, it can be the result of Coronal Mass Eject (CME) from solar activity.  But perhaps most sobering of all, is the possibility of a man-made EMP weapon that is purposely deployed in order to wreak devastation on our planet.  Scary stuff.

Regardless of the trigger, an EMP can be devastating to the power grid, resulting in rapidly changing electrical fields that will create fluctuating electrical currents and wild voltage surges.  Bottom line?  The electronic gizmos we have come to rely on would be toast.  The microchips would be fried or so severely damaged that they would become useless.

So what would life be like following a massive EMP event or episode?  There would be no power, no transportation systems, no communication systems, no banking, no internet, and, no surprise, no food and no water delivery systems.  This would truly be an End of The World As We Know it situation.

Ask yourself these questions:

What if the power went out and never came back on?  Could you fend for yourself?

Could you keep yourself warm in the winter and cool in the summer?

Where would you find food?

What would you use for money if credit cards and ATM’s no longer worked?

How would you get from one place to another without transportation?

How would you wash your clothes?

How would you keep yourself healthy if sanitation systems were no longer functional and medicine could no longer be manufactured.

And the biggest question of all, how would you communicate with the rest of the world?

An electromagnetic pulse could potentially fry the vast majority of all the microchips in the United States. In an instant, nearly all of our electronic devices would be rendered useless.

Back in 2004 the Wall Street Journal wrote:

“No American would necessarily die in the initial attack, but what comes next is potentially catastrophic. The pulse would wipe out most electronics and telecommunications, including the power grid. Millions could die for want of modern medical care or even of starvation since farmers wouldn’t be able to harvest crops and distributors wouldn’t be able to get food to supermarkets. Commissioner Lowell Wood calls EMP attack a “giant continental time machine” that would move us back more than a century in technology to the late 1800s.”

With that introduction, today I would like to introduce you to the Faraday cage, and further, how to build a simple Faraday cage.

The Faraday Cage

In the simplest of terms, a Faraday cage is any shielded enclosure that surrounds your electronic devices and protects them an EMP blast.  Commonly used enclosures include galvanized metal garbage cans, popcorn tins, and even tightly sealed metal filing cabinets.  In all cases, the metal container is lined with insulating material to prevent the contents from having contact with the metal.  Examples of insulating material are cardboard, Styrofoam, and even carpet scraps.

More elaborate structures can be custom built from sheet metal but for the home user, why bother?  As a matter of fact, I suspect that wrapping your devices in plain, ordinary, aluminum foil will work as well.

Factoid: Faraday cages are named after English scientist Michael Faraday, who invented them in 1836.

What About Using a Microwave Oven?

In my research I read that a microwave oven, new or used,  can be used as an effective Faraday cage.  On the surface, that seems logical since, by design, a microwave oven keeps the energy it creates confined to the interior which likewise, should prevent strong electrical pulses from getting back inside.

This was easy enough to test. I put a cell phone inside my microwave oven and tried calling it. It rang. Oops.  On the other hand, I wrapped my cell phone in aluminum foil and called it.  Nothing. Nada. No Michael Buble ringtone; the call went straight to voicemail.

Granted, cell phones operate at various radio frequencies so while one cell phone may not work, another one will.  Still, with this being so easy to test, why chance it?

Testing the Faraday Cage

Aside from calling a cell phone, you can test your homemade Faraday cage by putting a portable radio inside the shield after tuning it to a strong FM station.  If you can hear the FM station while the radio is inside your Faraday cage, then you need to go back to square one to ensure your shield is properly sealed.

Sealing your garbage can with duct tape will help tremendously.

A Second (Expert) Opinion

I asked my friend George Ure to comment and to offer his perspective on Faraday cages since EMP preparedness is something he covered in-depth on his subscriber site, Peoplenomics ($40 a year but worth it for the technical information on the many topics he covers.).

He was quick to point out several things about EMPs.  The definitive public information is contained In the 2004 Congressional Research Service (CRS) issued a report “High Altitude Electromagnetic Pulse (HEMP) and High Power Microwave (HPM) Devices: Threat Assessments”.  The following diagram shows how an EMP causes the complex systems we rely on to provide everyday essentials for living, to fail in a cascading manner.

So, a quick inspection of the EMP failure modes, George offers, is one way to build a list of items to put in your Faraday cage.

He also told me some personal research he’s done that seems to indicate that about 90% of cars will continue to operate after an EMP event of moderate size. The problem, he points out, is that with an EMP, the grid is likely to fail, and with that, power transformers will likely fail, along with the supervisory control and data acquisition systems (SCADA) control systems for railroads, power, water, and other utility distribution.

George’s personal Faraday cage is a 33 gallon garbage can.  He considers his metal garbage effective by itself because the metal lid overlaps the can itself by an inch and radio waves don’t like to go around corners, too well. Still, the ultimate prepping device would be a metal garbage can which has the top cover sealed to the bottom of the can with aluminized duct tape such as the type found at Amazon, Lowes, Home Depot and other hardware stores.

What to Put in the Faraday Cage

The equipment you store in a Faraday cage should encompass those devices that will help you communicate with the world following a devastating loss of the grid. Short-range communications will be critical. A good starting list would include:

Multiple GMRS radios and chargers along with cables to plug in for solar charging.

Multiple 2 meter and 440 MHz ham radios (such as the portable Baofengs), again with charging cables and solar power adapters.

A laptop computer with a fresh battery, a charger, solar adapter, and all the key software on CD so if you need to bring up a fresh copy of the operating system, you’ll have the product key and then any prepping articles or references you might need.

An AM/FM/Shortwave/NOAA Weather radio that includes a solar panel charging mechanism.

High-capacity USB thumb drive holding  pertinent financial information including past year tax records, scanned copies of birth certificates, passports, marriage licenses, deeds, vehicle registrations and medical records.

George also recommends simple insulation for your electronics, so that units do not touch each other, He uses low tech insulation: a combination of cardboard and bubble-wrap works well.

Protecting Small Electronics Day to Day

This article would not be complete if I did not mention the availability of small, shielded metalized bags that can be used to provide EMP protection on a daily basis.  I am currently testing this type of bag from Mobilsec and an quite impressed.  While my phone is in the bag, it reads “no service”.

If a cell signal cannot be detected, I can only assume that an EMP would also not touch it.  Good to know and certainly an option, especially for a laptop that could be placed inside a properly sized bag when not being used.  Couple the Faraday bag with a solar charging system and if there was an EMP, you would still have a working computer.

One other thing. You may find sources online that say that when a device is turned off, it will not need EMP protection.  I reached out to Joel Ho, the developer of the Mobilesec Bagsand asked him about that.  Here is what he said:

I’m assuming you are referring to the part about devices being off not needing protection – it’s simplified a bit – essentially, devices that are off are extremely difficult to damage because there’s no existing current to piggyback on.

Imagine that an EMP is a tidal wave.  If it approaches a full reservoir (electricity and current) it can keep going. If the reservoir is empty (no juice), the tidal wave loses energy navigating the reservoir.

There are hints of this in the article Electromagnetic Pulse Protection by Jerry Emanuelson.

The major reason [most sources] don’t say “your devices are safe if off” is because most devices are usually still connected to power lines and thus susceptible – but if devices are in EMP bags (which by definition are almost always disconnected as the filters are expensive), AND the devices are off, it is unlikely, given the relatively high FCC shielding regulations to prevent excess energy from bleeding OUT into the environment, that enough can get IN to damage those electronics.

This is NOT true for every device – more like a guideline than a hard 100% rule.  Different devices have different levels of built-in shielding – a computer has much more than a $10 Radio Shack timer, for example.

The Final Word

Should a massive EMP occur, stores won’t be open, credit cards won’t work, and the gas you have in your car may be all the gas you’ll ever have for months or even possibly years. When you think about it, an EMP will become the “Ebola virus of electronics”.

That said, you know that I am not a doom and gloomer.  Quite the contrary.  I am an optimist to the n^th degree.  Yet even the optimist is sobered at the ramifications of an EMP and especially at the prospect of a weapon-based EMP. If nothing else, I would like to have a mode of communication following a massive EMP.

Will the DIY Faraday cage work?  It is speculation to say for sure.  My own research plus my limited understanding of electronics tells me it will, but this premise will remain unproven until an actual EMP event occurs.

The bottom line is that I hope a catastrophic EMP never happens.  But if it does, I want to be ready to fend for myself without electronics. Sure, having communication gear and other electronic gizmos in a working Faraday cage will be a wonderful thing.  But even if it doesn’t work, the goal of preparedness is to prevail, even if that means living in an off-grid society for weeks, months, or even years.

I would like to acknowledge my pal George Ure for his assistance with this article.  His research and first hand experience with Faraday cages, along with his perspective, is appreciated.

Enjoy your next adventure through common sense and thoughtful preparation!