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What is a Faraday Cage and Why Should I Care?

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Every prepper worth his or her salt knows of the nightmare of an Electromagnetic Pulse (EMP). However, fewer are familiar with what a Faraday cage is and how critical they are to survival.

Whether the threat manifests itself as a man-made event (North Korea popping off a nuke at 300 miles up over Kansas) or natural (the sun burps out a Coronal Mass Ejection), the fear that EMP brings to my heart (and should bring to yours) it is a threat one cannot survive without serious preparation.

During our journey to ultimate preparedness we to stack beans, bullets, and band-aids high and deep. We ready our bug out bags (BOBs), bug out vehicles (BOVs), and bug out locations (BOLs). Some of us even prepare an underground bunker.

Most of these are well-rounded acquisitions that lend themselves to many possible events. But EMPs require special preparation in the form of a Faraday cage.

What is a Faraday cage you ask? Read on and maybe I’ll answer that and a few more questions that may come up along the way.

Threat of an EMP

As stated above the threat of an EMP attack comes from both natural and man-made sources.

A coronal mass ejection, or CME, occurs naturally when the dynamic surface of the sun pops a sunspot and thrusts billions of tons of charged matter (plasma) into our solar system. When this matter intersects our planet it electrically charges our atmosphere.

A man-made EMP results from a very high-altitude nuclear explosion. Indeed, the nuclear burst floods the atmosphere with gamma particles which induce a few free ions and charges the atmosphere just like a CME.

Regardless of the source, the effect is the same. The free charge bouncing around the atmosphere seeks an electrical path to ground. The most efficient way is via conductive materials. The larger the conductive surface, the more charge that is induced.

Electrical Component & Grid Failure

ESD sparks over RF electronics components

Within smaller electronics, the induced charge may be small but quickly overwhelms the tolerance of the small circuits. The result is burnout and failure.

For our electrical grid, the thousands of miles of power lines are literal EMP antennas that collect voltages beyond the capability of our grid. This voltage spikes race at the speed of light through the electrical grid.

This is all too overwhelming for the various components of the grid and the result is the failure of our power generation and delivery system. With numerous burnt-out components, the grid will go down and stay down.

Societal Failure

Within minutes all transportation and communication come to a stop. Within days (if we are lucky enough for people to be civil) the stores are empty and therefore bellies go empty. By the end of the week, there is complete chaos.

Ask yourself what would you do to feed your starving child? Do you think your neighbor will react the same way? I’ll answer that for you. Yes!

Within a month the United States experiences die-offs from starvation, lack of clean water, the diseases that follow, absence of medical care, and violence.

For those of a prepper mindset all is not lost. Besides your beans, bullets, and band-aids a must-have prep for EMPs is a Faraday bag. Let’s look closer at the question, “What is a Faraday Cage?”

Faraday Shielding

In 1836 Michael Faraday experimented with electricity and noticed that the charge in any given material was congregated at the surface. He continued with his research and ultimately built a room covered with metal foil and attempted to pass a large electrical field through the room.

As he hypothesized, the charge stayed on the outside of the foil and never entered the room.

Faraday discovered that the protective action of the Faraday shield effect (though not named as such then!) extended beyond electrical charge but also to other electromagnetic fields. The concept of Faraday shielding has been used ever since to isolate equipment from electrical fields.

From a scientific perspective, this is useful if you wish to run an experiment without interference. However, as a prepper, we use the same principles but to a different end.

Faraday Cage

A Faraday cage uses the Faraday shielding principle to protect the contents of the cage. Faraday cages are found at science centers or similar venues where the demonstrator stands in the cage between two Van De Graaff generators much to the fear and amusement of the audience.

Using the concept of Faraday shielding the bolts of lightning pass harmlessly around the exterior of the cage saving the demonstrator from a gruesome and spectacular death.

When approaching this from a prepping angle and a specific eye to EMP protection we need to modify the design from a cage to a solid conductive exterior. Enter the Faraday Box.

Faraday Box

A Faraday Box follows the concept of the Faraday cage but utilizes a solid conductive surface on the exterior and not just bars or a porous grid. This allows a broader spectrum of protection from lightning all the way through the radio frequency spectrum.

For maximum protection, a Faraday box is completely seamless. Protect any openings, e.g. around the lid with a tight-fitting joint using a conductive gasket or with an overlap of a conductive adhesive foil or similar material. The goal is to have no gaps in the protective surface.

Secondarily to the outside, the inside must include a layer of insulating material. Separate the sensitive electronics within from the outer protective layer. This is critical!

Likewise, it is not necessary to ground a Faraday cage or box. A quick review of YouTube yielded multiple demonstrations of no additional effect of grounding on the radio frequency cancellation properties of a Faraday Box.

The simplest examples include an ammo can and a trash can. For instance, the Trash Can Faraday Box is simply a trash can with an insulating liner (cardboard will do) and a tight-fitting lid.

The key is to ensure a tight fit on the lid. This can be accomplished with a length of metal foil tape or a layer of conductive gasket material installed inside the lid. Again, the key is no gaps in the conductive exterior.

An ammo can will make an effective Faraday Box if the waterproof gasket is removed and replaced with a conductive gasket and the paint along the top edge and the lid is removed, to allow for a conductive mating of the two surfaces.

Faraday Bag or Pouch

Mission Darkness X2 Faraday Duffel Bag
  • ✅ RF SIGNAL SHIELDING - Faraday bag blocks WiFi...
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Moving from the rigid to the flexible we have a Faraday bag. Faraday bags and pouches employ the same concepts as the Faraday box. They both completely surround the contents with conductive material. The difference with a Faraday pouch is that the conductor is flexible.

There are several materials that can be used for this including conductive cloth and aluminum-coated plastic (Mylar). Faraday bags are more convenient for the temporary storage of convenience items (e.g. a cell phone signal blocking device).

Faraday Cage Uses

So we’ve answered the question of What is a Faraday cage? Now it is time to focus on “why should I care?”

As stated previously, use the Faraday cage, box, or pouch to block electromagnetic energy. This energy can come in the form of radiofrequency waves (like a cell phone or WiFi signal) or the pulse generated by an EMP. By blocking or containing the signal we protect whatever is inside the cage.

Protection of Electronics

From the perspective of making an EMP proof container we use a Faraday cage to contain our sensitive electronics. Anything that you want to EMP proof goes into the box.

A shortlist of high-value items includes radios (ham, CB, GMRS, & FMRS), laptops, tablets, and eBooks loaded with your prepper library, cell phones, solar battery chargers, electronic medical supplies (e.g. glucose monitor, etc.), and electronic weapon sights.

Protection of Privacy

Use a faraday cage or bag to protect your data from authorities or hackers trying to mine your private information

Using a smaller Faraday device like a bag or a pouch you can protect personal devices from EMP as well as errant signal transmission. For example, putting a cell phone or tablet in a Faraday bag can block both incoming and outgoing signals.

We all know that many, many companies do everything they can to steal mine our personal data. They accomplish this by tracking our every electronic movement. Using a Faraday bag as a cell phone signal blocking device thwarts these companies in their efforts.

Likewise, use the Faraday cage WiFi blocking capabilities to keep your laptop or tablet safe during transport. Blocking both incoming and outgoing WiFi traffic the Faraday cage prevents your laptop or tablet from connecting to wireless access points and therefore reduces your digital signature.

DIY Faraday Cage

So let’s now address the next logical question: How to build a Faraday cage?

There are numerous articles on the subject so I’ll condense them into two of the most common projects (and one good bonus): garbage can Faraday cage, and an ammo can Faraday cage.

Garbage Can Faraday Cage

The garbage can Faraday cage is one of the simplest prepper projects. You will need three items: a steel garbage can, a roll of metal ducting tape, and an insulator (a few sheets of cardboard will do).


  1. Line the can with your insulator. Make sure to cover the entire interior.
  2. Put your sensitive items in the can, making sure that they do not touch the metal of the can and only come in contact with the insulator.
  3. Put the cover on the can.
  4. Wrap the seam between the lid and the can with the foil tape.
Behrens BEHRENS-RB20 Trash Can
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Ammo Box Faraday Cage

The ammo can version of the Faraday Cage is the second simplest prepper project. You will need: a steel ammo box/can, an insulator, and a conductive gasket or metal foil.


  1. Remove the rubber gasket from the lid of the ammo box.
  2. Sand all paint from inside the gasket groove on the lid and the top of the ammo box lip until you have removed the paint and exposed the shiny metal. This will ensure you have metal to metal contact.
  3. Line the gasket groove with the conductive gasket or a roll of metal foil.
  4. Line the inside of the box with the insulator.
  5. Put your sensitive items in the box, making sure that they do not touch the metal of the box and only come in contact with the insulator.
  6. Latch the ammo box lid closed.
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How to Build a Faraday Room

The ultimate in EMP proof preparations is the Faraday Room. When you make the decision to create a room-sized Faraday cage then the sky is the limit for what you can store. Generators, cars, complete COMMs systems, NVGs, and an armory full of electronic sights for an army of guns.

To construct your Faraday Room it is best to start with a room with limited entry points. Ideally, it will be a room with no windows and just a single door.

With the room selected, line walls, floor, and ceiling with several layers of metal foil. Make sure to overlap all seams and use foil tape on the seams of the outermost layer (to avoid peeling).

Cover the doorway and the door and apply a conductive gasket to all doorway contact surfaces. You will also cover all outlets and lights (it will be dark). The key is to have no gaps in the foil. Now simply shut the door to protect your precious electronics.


So what is a Faraday cage and why should I care, anyway?

First the “what”… There are many variants of Faraday cages, from boxes to bags, to rooms. Each once uses the Faraday Shielding effect keeping the electrical charge at the surface of the box away from the precious cargo inside.

Now the “why”… We make or buy a Faraday cage in the event of an EMP or CME. They are our only defense between working electronics and something that I used to use that is now junk. We also use them to protect our personal data and thwart data miners from poking even more into our lives.

It is worth every prepper’s time to investigate Faraday cages and how they can be used to extend their safety in this dangerous world.

Every prepper worth his or her salt knows of the nightmare of an Electromagnetic Pulse (EMP). However, less are familiar with what a Faraday cage is and how critical they are to survival.

Make a Faraday Cage That Fits in your BOB

emp electromagnetic survival course

Survival Sullivan came up with an easy Faraday cage that is lightweight and fits in your bug out bag.

In fact, they came up with one for your home or bug out location, that’s even more powerful. Make these two and never have to worry about an EMP again.

Dan Sullivan, one of the best prepping gurus out there, made this eye-opening video about EMPs. Lots of controversies surround the topic, but he’s setting things straight once and for all.

Hint: EMPs are about much more than Faraday cages. You need a bulletproof survival plan tailored to this specific event. Click here to see the two types of EMPs and why they’re likely to hit the U.S. at any time.