How Long does EMP or CMP Last?

EMPSomeone asked this question the other day.  So I thought that I would attempt to share some additional information this subject.

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

An EMP pulse  would occur in just a few one ten thousandths of a second. 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 electronic I had stored.  The reason for this is to allow time for a second weapon to be detonated.

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.

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.

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


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9 Responses to How Long does EMP or CMP Last?

  1. Rob Hanus says:

    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).

  2. MrApple says:

    Strange question, Will a pacemaker inside of a person fail from an EMP or CMP?

    • admin says:

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

  3. Alfred says:

    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.

    • admin says:

      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.

  4. Dave says:

    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!

    • Noah says:

      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.

      • Ajax says:

        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.

  5. Everett Cooney says:

    I thought the original topic was how long EMP effects last.

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