While working on my preps I found electrical specifications in the data sheet for the mylar-foil bags I was investigating for my food storage. This reminded me that many computer components (e.g., motherboards, hard disk drives, and expansion cards) are packaged in mylar-foil bags for ESD protection. I reasoned that since the ESD protection is provided by the conductive foil layer in the bag one should be able to use the same mylar-foil bags as Faraday cages to protect electronic devices and components from EMP.
One of the perks of my engineering career at defense contractor is that I work with genuine experts who deal with EMI and EMP issues on a regular basis. I ran my mylar-foil Faraday cage idea past a co-worker to make sure I wasn't missing something. In addition to designing EMP hardened equipment this individual is very like-minded with respect to survival and TEOTWAWKI topics. His response was that the mylar-foil bags offer good protection against EMP events due to their continuous and highly-conductive foil layer.
I think that mylar-foil bags offer several advantages when compared to the commonly recommended popcorn tins and ammo cans. First and foremost, sealed mylar-foil bags provide the water resistance near that of an ammo can without the bulk and weight. With one bag you can protect the gear in your BOB from both moisture and EMP! Also, the mylar-foil bags can be much more space efficient, especially for irregular shaped devices. Finally, these bags are inexpensive. Even if you don't have extras left over from your food preps you can visit your local computer store and usually find an assortment of them for the cost of your time.
If you choose to use salvaged bags make sure to stick with the mylar-foil style ESD bags. Avoid the bags that are clear, pink, or blue and those with printed patterns of conductive ink. If you can find them, I would recommend the mylar-foil bags with “zip-lock” style seals. These will allow one to periodically rotate the rechargeable batteries in their emergency gear without consuming material in the resealing process.
A word of warning: DO NOT use electronics grade mylar-foil bags for food storage! Bags that are not made specifically "food grade" for food storage may contain harmful chemicals and compounds that could leech into your food.
Many thanks for the great blog! Sincerely, - Kron