National Geographic Society

  • Connect:

Budget Prep: Faraday Cage

Protect Your Electronics From an EMP With this Simple Solution

DIY Faraday cage.

A simple metal trash can will act as a Faraday Cage.

Photograph by Rick Austin and Survivor Jane, Aleven Goats Media, Inc.

Inspired by prepper Kevin Poole's galvanized steel bunker with faraday cage, but lack the space or resources for such a large undertaking? We're bringing you budget versions of the preps inspired by our very own season three prepper builds.

What is a Faraday Cage?

A Faraday Cage is a conductive structure that acts as a shield against electromagnetic energy. Electromagnetic waves naturally flow around a surface of conductive materials, not through it, so by placing your electronics in a Faraday Cage you can shield them against an electromagnetic pulse.

To some preppers a galvanized steel bunker hidden deep in the recesses of their property would be the ultimate dream-come-true Faraday cage. Unfortunately, this dream would turn to pixie dust (for most) when the realization set-in of just how much a structure of this magnitude would cost, as well as the time, space, and resources it would require to build.  

But what if you could have the benefit of protecting your electronic devices from an electromagnetic pulse at a fraction of the cost? Say, the price of what the hinges alone would cost on the steel bunker?

What's an EMP, Anyway?

A galvanized steel trashcan would work in the same way the bunker would in protecting your electronic devices for a post-apocalyptic world.  But first, you need to understand how an electromagnetic pulse (EMP) works in order to understand how valuable this inexpensive item could be for your electronic preps.

Without getting too “techy,” an electromagnetic pulse happens when a nuclear event unleashes gamma rays above the atmosphere – either caused by a solar flare hurled from the sun or by a nuclear attack from a terrorist up in the atmosphere.  Gamma rays are extremely high energy photons and when they strike atoms in the atmosphere they knock large quantities of electrons free producing a pulse of electromagnetic radiation – an EMP.  At the speed of light, this electromagnetic pulse travels through the air and is also picked up in all telephone and power lines.  So if your electronic devices aren’t hardened or shielded; it could fry them… all of them. 

Things to Consider:

The critical point in making a Faraday Cage out of a galvanized steel trash can is to make sure the items you put into the trash can do not touch the sides, bottom or top of the trash can.  To do this, line the trash can with cardboard, including the bottom and up under the lid.  Before you place any item in the trash can – and as an extra measure – you can wrap the items in heavy gauge aluminum foil.  Once the items are wrapped, place the items you’re not likely going to need or get to right away on the bottom and then pack items that you may need to be periodically checked on top.  Once all your items are in the trash can, place the lid on securely; metal to metal, making sure nothing is caught in or obstructing the lid and trash can from making complete contact.  As an added step, you may want to tape the lid with a metal foil tape, to provide a total metal seal between the two surfaces.

Holiday cookie or popcorn tins can be used for Faraday Cages.

Photograph by Rick Austin and Survivor Jane, Aleven Goats Media, Inc.

But let’s say you don’t have the space for a galvanized steel trash can.  Not a problem. You know those cute tins we get at the holidays filled with cookies and candies?  Or, those huge tins filled with popcorn?  Those tins can be used as mini-Faraday Cages.  By placing those tins in numerous areas around your house as decorations, you could have quick and handy Faraday Cages at your fingertips, should you get notification that a solar flare is coming our way.  This is important because you may only have a few minutes to get valuables like cell phones into those cans.

Testing Your Set-Up:

To test your faraday cage, whether it is a big or a small can, the procedure is the same.  Take a working cell phone and put the volume as high as it will go. Then, place the cell phone in the Faraday Cage and put the lid on it.  Call the cell phone that you put in the Faraday Cage. If the Faraday Cage is working properly, you should not be able to call the cell phone. In other words, the cell phone won’t ring (if you hear the phone ring then the tin is not sealed well enough to keep out an EMP). An electromagnetic pulse travels just like radio waves, so if the radio waves going to the cell phone are stopped, then an electromagnetic pulse would be stopped too.

Keep in mind, no one knows for sure what will happen if we are struck with an electromagnetic pulse, but as the saying goes - two is one and one is none.  Or in the case of an electromagnetic pulse - all may be none if not protected.

Parts and materials.

The Steps:

  1. Line the walls and floor of the can with cardboard.

  2. You can line the cardboard with foam for additional protection.

  3. This 31 gallon trash can will hold all these electronic devices.

  4. Wrapping radios and other electronic devices in aluminum foil gives even more protection.

  5. Wrap your most important items in foil. Hearing aids, and other electronic devices you may not want to live without, could be invaluable after an EMP.

  6. Having a small solar panel, along with a battery charger and rechargeable batteries, can keep your electronic equipment running, even if the whole power grid goes down.

  7. You can make your own silica gel moisture absorbers with crystal cat litter and nylon stockings.

  8. Pack all your items so that none will touch the walls of the metal can.

  9. Place foam and/or cardboard on the top of the can.

  10. Place the lid on the can.

  11. Seal the can and lid completely by wrapping a metal foil tape around the top rim and the can.

The Doomsday Preppers articles, videos, links, images, and instructions (“Content”) are for entertainment purposes only. The National Geographic Channel makes no express or implied representations regarding whether the Content is up-to-date, complete, or accurate, and shall not be liable for any consequential damages, claims, losses, or demands of any kind based upon reliance of the Content. Do not rely on this Content for disaster, medical, health or safety advice.

murray bennett
murray bennett

Question. I wouldn't think so, but want to make sure. Rechargable batteries wouldn't need to be in a Faraday cage, would they? Also, in a pinch with only min.s to go, could you use your microwave as a cage?

Frank Traynor
Frank Traynor

Just one problem:  the sticky side of the tape may insulate the tape from the can and thus the tape would not be grounded...letting EMP into the can through voids between the lid and can? Better check for electrical continuity between the tape and can.

jeanne weaver
jeanne weaver

Would a Monolithic Dome Home be considered a faraday cage because of the rebar construction.

Thomas Samuelsson
Thomas Samuelsson

If you use a tin don't forget to remove the color around the edge of the tin and the lid.
Don't wire cable in to the Faraday cage from the outside this will puncture the EMC protection.
To wire cable in to another EMC-zone special installation is needed.
//Electrical engineer 

Thomas Samuelsson
Thomas Samuelsson

Tip, if you use a metal tin don't forget to remove the color around the tin edge och on the lid.
Do not wire cables from the outside of the Faraday cage to the inside, as this will puncture EMC protection.
// electrical engineer  

Neil McGillicuddy
Neil McGillicuddy

@jeanne weaver    I don't believe so. If you can recieve cell phone calls or pick up radio stations inside the dome it will not block an EMP. If you put your cell phone in a closed  microwave oven and call it, it should not ring, leaving he door open a crack will let the signal in. Windows, doors and other gaps are the weakness in a home like that. It doesn't take much gap to let a signal in.