Faraday Cages: What They Are and How They Block EMF Radiation

Last Updated on October 4, 2023

Faraday Cage
Source: sciencefacts.net

The year is 1836. A man named Michael Faraday is in England conducting an experiment using metal foil, a room, and some electric static charge.

After constructing a room coated in metal foil, he used an electrostatic generator to strike the outside of the room. Using an electroscope, he found that there was no electric charge present inside the walls of this metal-coated room.

Who is Faraday and what did he just discover? It’s a brilliant started-from-the-bottom story that resulted in the basis for an important physics field: Electromagnetism.

Who is Michael Faraday?

Everyone knows Einstein, Newton, and Edison. But Faraday isn’t as common of a household name, though modern technology has a lot to thank him for. He is often called the “Father of Electricity.”

A fun fact: Faraday was actually one of Albert Einstein’s heroes — he even had a picture of Faraday hanging in his study!

Michael Faraday
Michael Faraday

Faraday was born in 1791 outside of London, England. His family was not well off, and as the third of four children, he only received a basic education.

At 14 years old, he became an apprentice to a local bookbinder and bookseller. Because of this apprenticeship, Faraday had access to numerous scientific books, which he used to teach himself all about Electromagnetism and led him to become one of the greatest and most influential scientific minds of all time.

What is Electromagnetism?

An electromagnetic field is basically invisible energy that travels through the air in electromagnetic waves. This energy is called radiation, and varies in power based on the frequency of the wave.

The electromagnetic wave actually consists of two fields of energy moving perpendicular to each other: an electric field and a magnetic field. Electromagnetism is the interaction of these two fields, or currents.

Electromagnetic Field radiation, or EMF radiation, refers to the Radio Frequency (RF) fields and Extremely Low Frequency (ELF) fields that are emitted by technology as it transmits power and data.

At first, this radiation was not thought of as dangerous to human bodies, because it was too low in frequency to ionize (split) and damage cells.

However, now research is showing that this low frequency of energy can biologically change cell processes and communication.

Hundreds of studies have shown a correlation between EMF exposure and a wide range of neuropsychiatric effects. At the extreme end, EMF radiation can lead to infertility, cancer, behavioral disorders, and many chronic illnesses.

Faraday: The Father of Electromagnetism

Faraday had many contributions to the field of Electromagnetism, including his experiment with the metal-coated room demonstrating electromagnetic induction, which he discovered in 1831.

Faraday formulated that changing a magnetic field produces an electric field. In his experiment, he wrapped two insulated coils of wire around an iron ring. After passing an electric current through one coil, a momentary current was induced in the other coil. If he moved a magnet through a loop of wire, an electric current flowed in that wire.

This demonstrated Faraday’s Law: a conductor placed in a changing magnetic field (or moving through a stationary magnetic field) causes the production of a voltage across the conductor. This process of electromagnetic induction, in turn, induces an electrical current.

This discovery forged a foundation for Faraday’s future inventions, including the 1836 invention of the Faraday Cage, one of Faraday’s greatest achievements.

What is a Faraday Cage?

Vintage Faraday Cage
Source: nist.gov

Faraday cages demonstrate the concepts of electromagnetic induction, and reinforce the concept of electrostatic induction, which deals with electric fields.

Electrostatic Induction

Electrostatic induction describes what happens when an electrical charged current, or electric field, approaches a conductor.

The positive and negative particles in the conductor separate, and whatever the charge of the approaching object is, the opposite particle will swarm towards it.

For instance, if the approaching field is positively charged, electrons (negative particles) swarm towards it. Since electrons are no longer present in the rest of the conductor, it will have a positive charge.

It will create an opposing electrical field to the external object, insulating the interior of the cage from the external field.

Faraday Cage - How is Works
Source: nationalmaglab.org

Faraday discovered that an incoming electric field is diverted by the conductor, since the electric field rearranges the electrons in the conductor to neutralize any charge within the conductor. The Faraday cages take the electrical charge and redistribute it around the cage, rather than letting it penetrate through.

Faraday also illustrated this phenomenon with an ice pail experiment in 1843.

Electromagnetic Induction

However, that only describes half of the equation when talking about EMF energy. When a magnetic field reaches a Faraday cage, something else happens.

Like we mentioned before, a moving magnetic field always creates a current in conductors. This current is called an eddy current, and it creates an opposing magnetic field to block the waves from the interior of the cage.

Faraday cages are therefore able to block electromagnetic fields

There can be different types and levels of Faraday-style cages. The materials used to make the “cage” depend on the length, or frequency, of waves you’re trying to keep out and how much of the frequency you would like blocked.

To block these different frequencies at different attenuation levels, the type of conductive material used, the dimensions of the material, and the size of the holes in the material all come into play. The holes can range from a continuous substrate with no visible holes, to a true cage with large holes of a foot wide or greater!

Different metals possess different levels of conductivity. Gold is among the highest conductivity of any metal, closely after that comes Silver, then Copper. Aluminum is also a very good conductor for radio frequency waves. However, EMFs can pass right through steel and lead (even though lead can block X-ray frequencies). The higher the conductivity, the lower the chance is of electromagnetic radiation making it through the cage.

In addition, having holes may allow wavelengths to pass through to just beneath the surface. The smaller the holes, the shorter the wavelength has to be to get through. As the holes get bigger, bigger wavelengths (lower-frequency energy) can pass through. Because of this, Faraday cages can be thought of as “high pass filters.”

At the most basic level, high pass filters allow high-frequency signals to pass through, but blocks low-frequency signals.

Faraday Cages as EMF Protection

Because Faraday cages redistribute electromagnetic fields, there are important implications when it comes to protecting from EMFs (electromagnetic field radiation), which are emitted from every electronic device.

Perfect Faraday cages that completely encircle a person or device can potentially block out 100% of EMF radiation, if the right material is used. However, any device within the cage wouldn’t work because the signals needed for service would be blocked as well.

The good news is that we can still use the concepts Faraday discovered to make a two-dimensional shield instead of a cage, one that can act as a wall to block EMF radiation coming from one side. Of course, this shield has to have the right material characteristics to block out the specific EMF frequencies emitted by technology.

Real Life Examples of Faraday Cages and Shields

  1. Cars and airplanes. Both of these modes of transportation are basically giant metal cages. Due to their metal exteriors, cars and planes are protected from lightning strikes. If you’re ever stuck in a car during a thunderstorm or your plane flies through a weather system, you don’t have to worry about being harmed by lightning. If lightning was to hit either type of vehicle, it would simply redistribute its energy and continue on to penetrate to the ground. While EMF radiation behaves differently from electrostatic lightning strikes, it can still get stuck inside the vehicle, increasing interior radiation exposure. For example, for traveling reporters working in big media vans with screens, antennas, and wireless transmissions, EMFs are stuck inside with them (with some leakage). Learn more about how the Faraday cage affects EMFs while flying by checking out this article.
  2. Elevators. They aren’t built as Faraday cages on purpose, but because elevators are built with metallic conducting materials, they produce the Faraday cage effect. Many times, elevators will become “dead-zones” for devices that require external electromagnetic signals—cellphones and two-way radios for example. So, next time you’re about to enter an elevator, make sure that important text has sent and to finish any calls you’re on.
  3. Microwave ovens. Just as Faraday cages can keep an electric charge out, it can keep one in. Microwaves demonstrate the reverse effect. This common household kitchen appliance is built as a Faraday cage to keep the bulk of the microwaves contained to cook food, instead of radiating out into the room. However, some excess radiation has been shown to leak out—the FDA has approved a maximum of 5 mw/cm2 of leakage. A good test is to put your cell phone inside the microwave, close the door, and call it. If it rings, some RF/microwave signals are escaping.
  4. MRI rooms. Magnetic resonance imaging machines use strong magnetic fields and radio waves to create images of the body. The rooms around the machines are created as Faraday cages to prevent outside sources of radio frequencies interfering with the imaging, as well as preventing the excess amounts of radiation from escaping the MRI room.
  5. Military and government buildings. War rooms, operations centers, data centers, conference offices, and industrial spying, security, and intelligence rooms are often composed as Faraday cages. This is to protect the room and its confidential or highly valuable information inside from hacking, sabotage, eavesdropping, electronic theft, or even cyber warfare and EMP (electromagnetic pulse) attacks. They are typically steel roofed and sided to prevent electronic surveillance in addition to providing some level of protection against EMPs. This is known as TEMPEST (Telecommunications Electronics Material Protected from Emanating Spurious Transmissions.) However, those working in Faraday cages with electronic equipment are often at a much higher risk of EMF exposure, since emissions remain trapped inside the building.
  6. EMF radiation protection products. Most EMF radiation protection products are not actually considered Faraday cages, but are instead considered a Faraday-type shield. They use conductive shielding placed on only one side of the device, so the electromagnetic charge emitted from the device cannot exist on the other side. An example of a modern day Faraday cages are our Ultra Armor data security & privacy Faraday Bags with shielding that fully encapsulates devices to block all radiation and all wireless signals from coming in or getting out. This is what makes them great privacy pouches, since they prevent digital pick-pocketing, identity theft, and tracking.

The Verdict on Faraday Cages:

While you might think that living in a fully shielded Faraday cage would be beneficial in terms of EMF radiation protection, this might not be the case.

As mentioned before, EMF radiation might be blocked from going inside, but it is also blocked from leaving. If you have an electronic device in a Faraday cage-style building, the emissions from the device will not be able to fully escape, putting you at increased risk of exposure (you also won’t be able to receive a signal, and if you do, it won’t be as strong).

Additionally, the type of shielding you use, may not do much. Using a conductive paint on the walls to create a Faraday-style cage in a house might not be effective, because the conductor in the paint is a particulate. That means aluminum particles are spread in the paint, but there are many holes (that you won’t see). We recommend not using conductive paint, especially if it happens to be the quite-toxic lead paint, that EMFs can go right through anyway. Using aluminum foil might be more unsightly, but it would work better than paint.

If you have a cell tower close by, shielding only the wall facing the cell tower should be enough to shield you. However, if you have electronic devices close by, it still won’t offer much protection.

It is much more important to limit the sources directly around you that are transmitting wireless signals. Using some shielding for your mobile devices, WiFi routers, and/or smart meters offers you protection while ensuring the signals aren’t stuck inside your home.

In addition, turning off your electronic devices when you aren’t using them, and keeping them as far away from you as possible is a good rule-of-thumb for reducing your daily exposure to EMF radiation, while still enjoying the benefits of technology.

Unless you are extremely electromagnetic hypersensitive and have rid your home of all electronics, Faraday-caging your living space will probably do more harm than good.

Research has come a long way from the discovery of electrostatic and electromagnetic induction, but the recent introduction of current mobile wireless technology and its EMF radiation emissions has brought us to a whole new path of research and learning.

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Daniel T. DeBaun

Daniel T. DeBaun is an internationally recognized and influential expert in Electromagnetic Radiation (EMF) and shielding electronic emissions, with a particular focus on the effect of exposure from mobile devices such as laptops, tablets and cell phones. Daniel’s concern regarding the health impact of electronic radiation emissions grew from over 30 years of engineering experience in the telecommunications industry, where he held a variety of leadership and executive positions at Bell Labs, AT&T, SAIC and Telcordia. Daniel is co-author of recent bestseller, Radiation Nation: The Fallout of Modern Technology, a complete guide to EMF radiation safety and protection. Daniel is also a highly regarded industry consultant, speaker as well as frequent guest national radio and television programs discussing EMF health issues.