“A Faraday box is simply a metal box designed to divert and soak up the EMP. If the object placed in the box is insulated from the inside surface of the box, it will not be effected by the EMP travelling around the outside metal surface of the box. The Faraday box simple and cheap and often provides more protection to electrical components than “hardening” through circuit designs
which can’t be (or haven’t been) adequately tested.

Many containers are suitable for make-shift Faraday boxes: cake boxes, ammunition containers, metal filing cabinets, etc., etc., can all be used. Despite what you may have read or heard, these boxes do NOT have to be airtight due to the long wave length of EMP; boxes can be made of wire screen or other porous metal.

The only two requirements for protection with a Faraday box are: (1) the equipment inside the box does NOT touch the metal container (plastic, wadded paper, or cardboard can all be used to insulate it from the metal) and (2) the metal shield is continuous without any gaps between pieces or extra-large holes in it.

Grounding a Faraday box is NOT necessary and in some cases actually may be less than ideal. While EMP and lightning aren’t the “same animal”, a good example of how lack of grounding is a plus can be seen with some types of lightning strikes. Take, for example, a lightning strike on a flying airplane. The strike doesn’t fry the plane’s occupants because the metal shell of the plane is a Faraday box of sorts. Even though the plane, high over the earth, isn’t grounded it will sustain little damage.

In this case, much the same is true of small Faraday cages and EMP. Consequently, storage of equipment in Faraday boxes on wooden shelves or the like does NOT require that everything be grounded. (One note: theoretically non-grounded boxes might hold a slight charge of electricity; take some time and care before handling ungrounded boxes following a nuclear attack.)

The thickness of the metal shield around the Faraday box isn’t of much concern, either. This makes it possible to build protection “on the cheap” by simply using the cardboard packing box that equipment comes in along with aluminium foil. Just wrap the box with the aluminium foil (other metal foil or metal screen will also work); tape the foil in place and you’re done. Provided
it is kept dry, the cardboard will insulate the gear inside it from the foil; placing the foil-wrapped box inside a larger cardboard box is also wise to be sure the foil isn’t accidentally ripped anywhere. The result is an “instant” Faraday box with your equipment safely stored inside, ready for use following a nuclear war.

Copper or aluminium foil can help you insulate a whole room from EMP as well. Just paper the wall, ceiling and floor with metal foil. Ideally the floor is then covered with a false floor of wood or with heavy carpeting to insulate everything and everyone inside from the shield (and EMP). The only catch to this is that care must be taken NOT to allow electrical wiring connections to pierce the foil shield (i.e., no AC powered equipment or radio antennas can come into the room from outside). Care must also be taken that the door is covered with foil AND electrically connected to the shield with a wire and screws or some similar set up.

Many government civil defence shelters are now said to have gotten the Faraday box, “foil” treatment. These shelters are covered inside with metal foil and have metal screens which cover all air vents and are connected to the metal foil. Some of these shelters probably make use of new optical fibre systems–protected by plastic pipe–to “connect” communications gear inside the room to the “outside world” without creating a conduit for EMP energy to enter the shelter.

For larger items which cannot be boxed, such as living room TV sets, etc, I tape a Mylar space blanket to a piece of 6 mil black plastic sheet, using double-sticky tape every foot or so to make sure the Mylar stays in place (it is slippery). I leave a 2 inch edge of black plastic showing all around the space blanket, and while taping down the edges I put on a short lead of ground wire. When it appears that EMP or CME’s are on the way, the blanket can be draped over the appliance, the alligator clip attached to a small, unobtrusive ground wire behind the cabinet, and any electromagnetic radiation will be diverted to the ground wire. Very cheap, simple, and once done, items can be “draped” for protection very quickly indeed. The “EMP Blankets” roll up for storage, but can be unrolled and thrown over a TV/VCR setup, a computer/monitor combo, etc. As EMP comes from altitude and is line of sight, it’s OK that the bottom isn’t covered, as the bottom of the units sit on non conductive wood.

The time to build Faraday cages or blankets is NOW, as when they are actually needed it will be far too late. Each box should be labeled on the ends and the top for the exact appliance they were built for, to eliminate any confusion when they must be protected in a hurry. Any electrical appliances not in use should be stored in the Faraday cage, where they will be kept clean, neat, in a known location, and protected against any sudden EMP surge

NOTE: There are electrical engineers who say that only ferrous metal boxes will protect against EMP-enhanced weapons, while other sources say EMP is not a problem at all. I’ll take the middle ground.”

http://www.whenshtf.com/showthread.php?11095-EMP-Protection-and-Defences