One of the most devastating, and sadly, one of the most plausible, mega disasters that preppers worry about today is that of an EMP, or electromagnetic pulse.
Generated by the detonation of a nuclear warhead, a specialized EMP device or even powerful cosmic phenomena, a potent EMP can completely destroy the electrical grid, anything connected to it and many other electronic devices. Accordingly, EMP protection is near the top of major disaster preparations.
Some folks claim that common mylar bags can be used to protect electronic devices from the effects of an EMP. Is it true?
No, typical mylar bags will not provide significant protection from the effects of a powerful EMP. Although these bags usually have a metallized coating, it’s not adequate to protect items inside from the most threatening EMPs.
It is difficult to say just how bad the consequences of a major EMP could be. A total blackout is all but certain, and many electronic devices will be temporarily offline with damaged components or even completely destroyed.
It’s certainly in your best interest to protect the devices you depend on against EMPs, but I don’t think a common mylar bag is going to do it. I’ll tell you why below…
What Exactly is a Mylar Bag, Anyway?
To make sure everyone is on the same page when it comes to mylar bags, we were referring to PET plastic bags, the kind that is usually, but not always, made with a super-thin aluminum skin on one or both sides of the plastic itself.
PET, an acronym for polyethylene terephthalate, is a ubiquitous type of plastic that’s used to make everything from packaging for food and other goods to plumbing components, clothing, water bottles, and a whole lot more.
This plastic has a good reputation in these applications because it provides a good seal that will keep oxygen out and also resist degradation from oxygen and many other environmental factors.
Lightweight, inexpensive and effective, PET has a lot going for it, and mylar bags are some of the very best you can get for food storage or for storing anything that needs protection from the elements, including moisture and pests.
But the big question that we need answered is whether or not mylar bags can and will protect electronics placed inside them from the damaging effects of a major EMP.
The Popular Case for Mylar Bags
The popular case that is sometimes sincerely, but erroneously, made from mylar bags as EMP protective enclosures is based on the fact that they can sometimes block various cell phone and other radio signals, in addition to being advertised for static protection as described above.
The test, such as it is, that is usually performed is a person placing a cell phone or other device inside the mylar bag before closing it and then trying either to receive a call on the phone or place a call with the phone.
People also demonstrate various bluetooth devices and other connected electronics that will or will not sometimes lose communication with the host device inside the bag.
The reasoning is that, because these signals are being blocked, the harmful emanations of an EMP must likewise be blocked. This determination is false: those with even a little bit of experience or theoretical expertise with electrical theory will quickly see the flaw with this testing protocol.
Cell phone signals are electromagnetic waves themselves, but they are far, far weaker than the potent emissions of a major EMP. Cell phone and bluetooth signals are relatively easy to interfere with, and a variety of materials, not just metal, will successfully do it.
Defeating these low-power waves is not evidence that the same material can defeat EMP waves coming from the other direction.
But there are other shortcomings in this equation besides the premise of the test and the supposed evidence itself. I’ll tell you more about them in the next sections…
The Metal Coating on Mylar is Insufficient for EMP Protection
One of the major shortcomings with metallic mylar bags as EMP protective envelopes is that the component that actually provides the protection, the aluminum or other metal, is simply insufficient for the task.
Mylar bags are incredibly thin, and the metallic skin that is applied over the plastic is even thinner.
This simply will not provide enough of a barrier to completely enclose the protected electronics via the Faraday cage approach.
Looking at purpose-designed and built or improvised Faraday cages that are likely to offer significant or total protection against an EMP, we will see they are invariably made of multiple layers of metal foil, metal mesh, solid metal paneling or other substantial metal material.
An EMP is going to be a significant electrical event, and the generated waves must be deflected, absorbed or redirected completely and adequately enough to protect the vulnerable electronics inside the cage.
Any metal that isn’t thick enough will allow the emanations to reach past the surface to the interior, endangering the protective device.
Typical Mylar Bags Have Inadequate EMP “Sealing”
Another principle of EMP protection via Faraday cage to keep in mind is another one where mylar bags again fall short.
A Faraday cage must offer a complete enclosure of the protected electronics and be sealed shut on all sides, with no gaps or weak points where the EMP waves could penetrate or “squirt” through to the interior.
Metal-to-metal contact, or specially constructed gaskets on larger containers are required for assured protection, and common Mylar bags just don’t offer it.
They might get close, assuming they are vibration welded or otherwise permanently bonded somehow, but common zipper, clicker or slider closures on these bags are just not sufficient for the threat.
Any of these closure types are weak spots that can allow EMP waves to easily access the interior of the bag, completely compromising whatever assumed protective value is there in the first place.
Something else to keep in mind is that even in the case of vibration-welded, vacuum-sealed or heat-sealed closures there has been basically no real word testing performed using Mylar bags against powerful EMP sources.
As you might imagine, common at-home tests are not proof of adequate protection, as described above.
At best, the level of protection is going to be marginal. At worst, it will give you a false sense of security and let you down on that fateful day.
Serious EMP Protection Requires Purpose-Designed Solutions
If you are serious about providing EMP protection for your vehicle, tools or devices, then it’s time to get serious about crafting it yourself or properly investing in it.
I am not claiming that it is impossible to craft your own completely effective EMP protection.
The principals are easily understood, even though publicly accessible data on the effects of the most powerful EMPs, and how our devices handle it even when protected is sketchy to non-existent.
In theory, you should be able to craft worthwhile protection using a little bit of elbow grease, ingenuity and common building materials. That said, mylar bags just don’t have a place in your arsenal.
Alternatively, you might find it more cost-effective to purchase purpose-designed EMP protective enclosures, of all sizes, from manufacturers and retailers that specialize in the sector.
Whichever way you decide to go, it is old but certain that you’ll wind up with superior protection compared to a common mylar bag.
Understanding these principles and figuring out the best approaches is a fairly lengthy conversation, and you’ll find lots of information here on that very topic.