How Long does an EMP or CMP Last?

I was asked the other day what are EMP’s and CMP’s, and I thought I would do my best to share my knowledge on the similarities and differences.

First, while EMP and CMP are different both can cause the same type of damage to electronic devices.

What does an EMP do?

An EMP pulse would occur in just a few one ten thousandths of a second and has the capability of permanently damaging any electronic device.  That is what makes it so dangerous, it occurs so quickly that there is no warning.  It is thousands of times more powerful than lightning strikes and occurs many thousands of times quicker.

They will only occur as a weapon is detonated and there may or may not be a second detonation.  Personally, I would wait at least twenty-four hours to break into my Faraday cages and retrieve any electronics I had stored in case a second weapon is detonated.

More devices than you might realize could be affected by both EMP and CMP — not just computers and cell phones:

  • Solar panel systems
  • Cameras
  • LED flashlights
  • Walkie-talkies

Think about what you might want and need to provide you with massive survival advantages and prepare to store them in a Faraday container.

What does a CMP do?


CMP or Coronal Magnetic Pulse is cause by solar storms.  Examples would be the Carrington Event in 1859 which lasted 2 days.  Intense storms typically last 1-3 days and the surges are like a continuous series of waves.  Today we should have from 24 to 92 hours of warning. That’s enough time for the utilities to shut things down in a controlled fashion, if they heed the warning.

The dangers of an EMP or CMP event are real.  The electric grid is old, in some cases well over a hundred years in age, it also lacks essential backups to prevent outages. According to a 2014 report from the Library of Congress’ Congressional Research Service, “Despite their great size and internal complexity [high voltage] transformers can be readily disabled or destroyed.”  Most of these transformers are no longer manufactured in the US.  Many come from China.

See also  10 Preps For Your Nuclear-Event Go Bag

A study by Penn State University found that, “This vulnerability of the electric power grid is inherent to its organization and therefore cannot be easily addressed without significant investment.”

In case of a major event of either type you would expect to have a large scale failure of the power grid that could last from 6 months to years.  At the same time, many vehicles would fail and many smaller electronic items would fail.  There is a lot of questions about radios and other small devices that were not plugged in, some people think they would survive.  There seems to be a lot of confusion in the information that is available on this subject.  I would error on the side of caution.

You can protect small electronic items by building a faraday cage.  A faraday is defined as an enclosure formed by conductive material or by a mesh of such material.  Such an enclosure blocks external static and non-static electric fields by channeling electricity through the mesh, providing constant voltage on all sides of the enclosure. It is important to have one of these in case we do have an EMP.

The following links provide additional information on EMP, CMP and improvising homemade Faraday cages.

Updated July, 2020

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10 thoughts on “How Long does an EMP or CMP Last?”

  1. There is an important distinction between EMP and CME. A CME will not fry electronics if they’re not connected to the power grid, as an EMP will. Anything connected to the power grid during a CME *may* get fried due to the power surge, but much of that depends on where the surge occurs. IOW, you don’t need a Faraday cage to protect electronics from CME.

    The big issue with CME and EMP is these events will melt the large power transformers in the power grid, rendering the grid useless. We don’t make nor store these large transformers here in the states, so replacing them after an EMP/CME event will take a Herculean effort by the remainder of the world (assuming they don’t have their own problems to contend with).

    1. I don’t know for sure, but I think it is a possibility. Maybe someone out there has a good answer.

  2. My understanding of EMP is that it has the potential to induce current in anything conductive. I also recall reading that those massive transformers and other large mechanisms used in the power grid must be ordered years in advance, because assembly takes that long.

    1. You are right but a lot depends on the strength of the emp. The smaller the target the better chance the emp will not affect it.

  3. Hmmm, My understanding, and excuse me if I’m wrong, (it wouldn’t be the first time) But with the polar fields racing around as they are now doing and scientists talking global “magnetic flip” or “reversal”, and with the recorded rapid weakening of our protective magnetic field that surrounds the earth, any “solar events” need not be strong to adversely affect our “system”.
    In other words, “solar events” such as CME’s that our world “shrugged off” in the past are now likely to cause nasty negative events world wide. (or what we will perceive as negative eh?)
    We do live in an electromagnetic universe and I’m afraid our understanding of our reality is greatly limited to say the least.
    Check out the Suspicious Observers channel here on YouBoob, … They are on the cutting edge of observable and provable sun science.
    All the best and good luck.
    Oh yeah, … what use will electronics that are saved by a faraday cage be if the whole electronic system is down? Radios when there is no signal to receive. I’m pretty sure satellites will be a thing of the past, so there goes your GPS. Phones?
    Things will be radically different even for those of us who think we are prepared, let alone those who are have totally “bought in” to todays societal structures.
    Societal structures that are flawed to say the least. Unless you are to argue that eternal wars, millions of starving children in the world, uncountable homeless and destitute, not to mention the horrendous environmental disasters occurring hourly, are the result of a healthy, wealthy, and respectful society.
    Oops! Getting too real. Sorry.
    have a great one!

    1. I’ve come across your question about preserving electronics in a Faraday container because they’ll be completely useless. There’s another way of looking at that, though. Think about all the information that can be stored in lightweight and compact devices — entire medical manuals, textbooks, survival information, etc. Information, alone, increases survival odds. As well, it gives you an advantage over others without that information. Our partner site,, has an article that addresses this issue,

      If you have a few solar chargers, you’ll be able to charge these devices indefinitely.

      1. Until the lithium ion batteries that mobile device makers like to use die.

        These batteries are typically rated for a life of two to three years or 300 to 500 charge cycles, whichever occurs first. Keeping them charged up at 100% is damaging, fully discharging them kills them, and they also self-discharge. If you pack away a li-ion device in a faraday cage, and it’s been sitting idle for a few years, it’s quite likely the battery will hold no longer hold a charge.

        A better choice of battery tech is eneloop nimh rechargeables. These are rated for 2000 cycles and have low self-discharge, so they will retain 70% charge after 5 years. And taking them out of a faraday cage and charging them up every couple years isn’t the worst hardship.

        The only problem with eneloop is you’ll need tech that uses traditional battery form factor (AA, AAA, …) or your devices need to be converted over to use traditional form factor. You may be able to use some dead phones and e-readers if you power them over USB from a battery bank that uses the eneloops, but it depends on the device, so no guarantees here.

        I agree with your overall premise about the value of these devices, if you’ve planned ahead and stuffed them with offline content. I just urge caution and careful planning when relying on lithium-ion battery based devices.

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