Testing Faraday Bags

Testing Faraday Bags

Do Faraday bags work? There’s a lot of misinformation about what a Faraday cage (or bag) protects against.  The basic belief is that Faraday bags are designed to block radio wave transmissions, act as an insulator to protect against electronic currents, block tracking and hacking.  Federal agencies and local law enforcement officers use them to protect information and evidence (cell phones or laptops) from being hacked and tampered with.  Preppers use them as a precaution against an electromagnetic pulse (EMP) from a bomb or astrological event.  Nonetheless, are all Faraday cages and bags created equal and how protected are we really?

Mylar Bags vs Faraday Bags

Mylar bags and Faraday bags look the same so how are they different?

Testing Faraday Bag - Mylar vs Faraday

Mylar bags are made of a transparent polyester resin and coated with aluminum.  The thickness of the Mylar bag is 3.5 mils.

A Faraday Defense bag has five layers made up of static dissipative polyethylene (plastic), aluminum, polyester, aluminum, and the final coat dissipative polyethylene polyester.  The thickness of it is 7 mils.

The thickness and protection from light is apparent in the picture above.


Testing Faraday Bags

I decided to try some basic tests with the Faraday bags before stashing them away and I am so glad I did.  The outcome of the tests were surprising!  It definitely changed how I’ll be protecting my electronic devices.  Supplies used to conduct the tests:  tinfoil, cell phones, walkie talkies, a radio, and two Faraday Defense bags.  Watch the following video to see if the Faraday bags work.



What is a Faraday Bag Designed to Block?

Not all Faraday bags offer the same protection. The most basic Faraday bags are designed to block electromagnetic interference (EMI). Electromagnetic currents can damage electronics. Attenuation or dB is what you’re looking for when shopping for Faraday bags. Attenuation is the measurement of how effective the shielding is. Anything above 60dB is considered very good protection.


Since the bags failed two out of the three tests, it raised the question:  why didn’t they block the radio frequency better?

I would like to address your concerns if possible to help clear up questions:
1. Our listing does not claim to block cell phones or walkie talkies – these are EMP bags for protecting items from EMP frequencies causing damage to electronics (they are not bags blocking cell signals – we do carry a full line of privacy bags if this is what you’re after)
2. Much like lightning will pass on the outside of a car (faraday cage) but not harm inhabitants, so an EMP bag acts as a path of least resistance for EMP frequencies to reach the ground.
3. A car will still easily allow a cell phone call or radio signal, but the car itself can block an inhabitant from a direct lightning strike.


The bags you see above DO NOT block radio-frequency interference (RFI), RFID, GPS, WiFi, or cell phone signals. They are just designed to block electromagnetic interference. There are Faraday bags that provide more protection. Sometimes, they are called privacy bags or blocking bags. These bags are designed to protect devices from hacking and tracking by adding more protection.

After researching and testing the Faraday bags,  I’ll be adding extra protection to each electronic device.  Each item will be wrapped in plastic to act as an insulator, then wrapped in two layers of tin foil, and lastly placed in the Faraday bags for anti-static shielding.

There are a couple of things I liked about the Faraday bags.  First, I like that the bags seal completely.  The zip-locking seal also protects the contents from moisture. Second, it’s easily accessible and compact, unlike most Faraday cages.


Ideas on What to Store in a Faraday Bag


  1. laptop
  2. cell phone
  3. solar charger
  4. solar light
  5. tablet
  6. walkie-talkies
  7. radio (NOAA emergency weather radio, AM/FM, shortwave radio, ham)
  8. external memory devices
  9. calculator
  10. alarm clock
  11. small DVD player with monitor
  12. glucose tester

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Welcome to my site! My name is Nettie and I started this blog to provide simple tools to help Preppers.  I am a Girl Scout Prepper. “Be prepared! A Girl Scout is ready to help out wherever she is needed. Willingness to serve is not enough; you must know how to do the job well, even in an emergency" (the motto, in the 1947 Girl Scout Handbook). Being a Prepper has been a blessing to me, my family, and friends on more then one occasion. You'll find these stories throughout this blog.  You will also find prepper supplies checklists, prepper events, cheap food storage ideas, emergency heat sources, survival books recommendations, reviews on power outage lights, printable prepper pdfs, and articles on emergency disaster preparedness.  Click here to read more

11 Comments on Testing Faraday Bags

  1. Nice article. Though I’ve tried these bags and they don’t really seem to work that well. I used the md faraday bags tester app and they didn’t block wifi or cell signals. Just FYI as I recently got other bags and they do the trick. I know that EMI protection relates to radio frequency blocking, they are similar in effect. If the bag blocks radio frequencies it will likely block emi. Thanks for the info, you did a nice and thorough job. I am a big fan of this site and we take a lot of tips from here. Thanks!

  2. A Faraday Duffel Bag? Does anyone know how heavy that can get? My sea bag hit around 66 lbs. with just issue clothing (commercial air travel max load at the time. I can easily get 100 lbs or so of “essential” clothing into a duffel / sea bag. Electronics are denser and more fragile than any towel or coat. I have a number of transceivers that I do not co-locate do to the potential threat of loss. A bag of this size MAY be handy as I do not know what Jeannie or someone else has in mind. I would offer turning one’s garage into a Faraday Cage would be a potentially better solution.

    • Gunz, You really could turn a garage into a Faraday Cage? I never gave much attention to preserving electronics in the event of wide spread emp wipe out, basically because of 1) the cost of Faraday Cages 2) would need alot of them and ultimately like you state 3) bulk and weight which without a vehicle would make them immobile. 4) the chances that what ever item I want to protect, I cant afford multiple of them, to have one always protected and put away and another to use (such as laptop), it will without doubt NOT be protected cage when shtf.

      Yet you raise an excellent alternative option if its doable and relatively low cost if done ourselves. Please elaborate

  3. Excellent test. Thank you. I think I’ll get more aluminum foil to wrap my electronic things in. Along with paper towels for moisture, plastic baggies for water proofing then aluminum foil for emp’s and cme’s that should be good. 🙂

  4. So, what you are saying is that Faraday Defense bags don’t work as advertised. I use .50 cal ammo cans and 10 gallon galvanized steel garbage cans to store sensitive items, such as radios, GPS, etc. They work!

  5. Just an interesting point for everyone. Where I live, metal roofs and stucco walls are normal, stucco is usually placed on chicken wire attached to the walls of the house. This in itself can help you protect your equipment, notice I said HELP. This along with a 10 gallon steel garbage bag. My hope is that my equipment will be safe if an EMP event happens.

    I use the EMP Defender bags and have tested them using both cell phone and radio. Put them in a bag, then into the garbage can. I closed the lid and tried to call the phone. No ring. I then turned on the radio very loud. Put it into the EMP bag, there was a signal decrease along with some fairly heavy static. Placed the radio in the can and it went dead with the exception of static. I’m hoping that I’m protected during such an event.

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