What to do if you find high EMF levels
The Four "D"s of Reducing EMF Exposure:
1- Diagnose with a meter
This step is the key to a successful mitigation. Even if you know you are bothered by a specific device (your wifi router for example), there will surely be other sources of EMF in your environment which are contributing to your exposure burden, and so raising your overall sensitivity.
EMF Meters are easy to use and are affordable, and they are the only way to identify hidden sources of trouble. And they can help you check if your efforts have indeeed resulted in reducing the overall exposure.
Depending on the source of the high fields, there are several strategies for reducing them:
2- Increase your distance
Like heat from a candle, EMF strength decreases with distance from the source. Here are some common examples of how to increase your distance:
3- Turn off the source
Turning off the source of the field results in immediate and complete reduction of the problem. Turning off could look like this:
Turn it off permanently
Shielding involves placing a proper barrier between the source of the EMF and the people. There are many types of shielding material, and it is critical to choose the right one, in the right quantity, and install it in the right way. The shielding material can often be placed directly on the source of the EMF, or perhaps on or near the body of the person. We are always willing to assist you in choosing the proper material for your situation.
Here are some common examples:
How Can I Shield a Whole Room from Radiofrequency?
The concept of radiofrequency (RF) shielding is simple: simply put a barrier between the source of the radiation and the area you want to protect. But keep in mind that in many ways, RF behaves like light and can reflects off of some surfaces… working its way around any shield which is less than a complete enclosure.
Image that you are outdoors on a sunny day. You set a large mirror on a stand above your head. The attenuation for the mirror is very high, perhaps 120 dB or more, so basically no light comes through the mirror. If leakage was not an issue, you would be in total darkness. We all know this is not the case. Leakage from the sides easily illuminates the shaded area. Granted, the amount of illumination is less than standing in full sunlight, but the attenuation is nowhere near 120 dB. Maybe more like 20 dB. Furthermore, using a shield with even better attenuation will not yield any more benefit.
To achieve a high level of shielding, you must control leakage VERY carefully. Gaps under doors, joints between shield sections, and even pinholes from sewing shielding material can permit these high frequency signals to penetrate. You need to create a "complete" enclosure. Any part that is not shielded is a leakage point.
In addition, it is critical that you remove RF sources which are inside the room. Check with an RF meter for cordless phones, wifi routers, laptops, baby monitors, etc. An RF meter will also guide and evaluate the effectiveness of your shielding installation.
Windows will most certainly permit RF to enter the room. Think about the type of windows you have and whether or not you plan to open the windows. There are 3 basic approaches to shielding windows:
Actual photos of various windows shielding materials:
Shield the walls and ceiling
Painted surfaces are easily shielded with CuPro-Cote® or Y-Shield paint. This includes trim and doors. Be sure to caulk and gaps or cracks prior to painting so that you have a continuous, unbroken painted surface. You can paint over the shielding paint with any color of latex paint to achieve any appearance you like. You could also use a shielding fabric such as Nickel Copper RipStop or AL60 behind the wall. Attach these materials directly to the studs before installing the drywall. Pay attention to whether or not a vapor barrier is desired in your location.
Floors are best shielded during construction. The subfloor can be painted, or a shielding fabric layer can be applied before the final floor surface is installed. If the floor in already installed, you can lay shielding fabric, and cover it by a large area rug or sheet linoleum.
How can I shield my Smart meter?
A Smart meter is a radiofrequency (RF) emitting device that the utility company has installed on your gas or electric meter. The RF signal emitted transmits information back to the utility company about your gas or electric usage. The signal is intermittent, but operates 24/7. Usually, the utility company will not permit you to completely block this transmission. However, you can shield your body and your living space to minimize the amount of RF exposure you receive.
There are two main categories of shielding materials that can be used:
RF reflectors and RF absorbers
An RF reflector will cause the majority of the signal to bounce off, somewhat like a mirror reflects light. It can have very high shielding performance, and in general should be grounded for peak efficiency. It will usually offer better shielding (less RF transmission) than an absorbing material. An RF absorber will absorb the much of the signal, and minimize reflection. The energy absorbed is released as a tiny, almost unmeasurable amount of heat. Grounding is usually not needed. In both cases, SOME amount of RF does get through the shield, as no shield is 100% effective. You can use double or triple layers of shielding to improve performance.
So where should I put the shield? And how much area do I need to cover?First, the shield must be positioned BETWEEN you and the source of the radiation. Generally, this means that the shield will be placed on the interior surface of the wall adjacent to the Smart meter. Think about the Smart meter emissions as coming from a light bulb located at the meter, and the shield casting a shadow. Cover enough wall so that the people would be in the protective "shadow" cast by the shield. Notice the small shield in the floor plan at right. In this example, the majority of the bedroom area is protected, but that is not true for the rest of the living space.
So which one is right for your situation? In a hypothetical world where your Smart meter is the only source of RF radiation, either absorbers or reflectors would work well. However, in the real world, there will be multiple sources of RF radiation. Some of them might be right inside your own home. Some might be coming from other directions. In such a situation, if you use a reflecting material, it will reflect on BOTH sides, and you could end up increasing the amount of RF in your living space. On the other hand, if you use an absorber, it will absorb on BOTH on both sides, so you cannot increase your exposure. If, you use both materials, a reflector on the side closest to the RF source, and an absorber on the side closest to the living space, you get the best of both materials... and the absolute lowest RF transmission. Any small amount of Smart meter signal penetrating the reflector will be absorbed by the absorber. Any signal coming from the opposite direction will have to pass through the absorber, then reflect off the reflector, and finally pass through the absorber again before it re-enters the living space. This would be a very small amount indeed.
How can I shield magnetic fields in my car?
Magnetic fields are common in automobiles. Even cars with gasoline engines can have high levels, depending on the wiring configurations and the locations of the tires and other moving engine parts relative to the passengers. Electric or hybrid vehicles can have very high levels due to the high current demand and re-charging mechanisms. Every vehicle will have multiple sources of magnetic field, some of which may be in areas that are difficult to access for shielding. With persistence, a satisfactory reduction of field levels is usually achievable. But don’t expect the levels to drop to zero.
Begin by diagnosing the fields in your vehicle. Use a 3-axis gaussmeter with a range of at least 200 mG, and flat frequency response.
Select a location away from powerlines and other sources of background magnetic fields. Notice the background level with the car not running. You will subtract this number from all further meter readings. Park the car, but leave the engine running. Slowly move the gaussmeter in the passenger areas. Check all areas that will be occupied by passenger bodies, including the seat, head, and floor areas. If you have an electric or hybrid vehicle, you should have an assistant drive the vehicle while you make meter readings. Check during the various modes of power: electric only, gas only, accelerating, cruising, braking, etc. Identify areas which have high levels (above 3mG).
Next, for each “hot spot”, sweep around that immediate area looking for the source of the high field. Naturally, the true source may be hidden under the floor, behind a panel, or on the other side of the firewall. But identify the accessible area closest to the source. This will be the surface with the highest readings. Remember to check under the dash as well!
Starting with the area with the highest field, place the meter in a location which you can find again after shielding is installed. You may need to measure its position relative to landmarks in the car, such as bolts, wires, etc. It is important that the meter position be repeated in exactly the same position (before and after shielding), as changing the meter position will change the readings.
Now lay a piece of shielding in the area of the hot spot. Magnetic Shielding Foil was used in this example. Giron is also a good choice. (Caution! The edges are sharp!) Use the largest piece of shielding that will fit. You can always trim edges or corners to work around odd shapes. If your largest piece of shielding is not wide enough, you can place pieces next to each other, with 1-2 inches of overlap where they meet.
Later, you will lock these pieces in position and cover them with protective carpeting. It is imperative that they do not come loose and create a driving hazard!
Complicated shapes and multiple barriers in a vehicle may not permit the placement of shielding in all locations that need it. You have to accept some level of compromise because of these limitations.
Now, place the meter back in the same position and take a reading. The level should be lower. Sweep around the shielded area to identify the remaining “hot spots”. You may need to add more shielding to the edge of the shield. Or try another layer of shielding. Or you may need to shield an area opposite the shield (In this example, we shielded the driver’s foot area, and needed to add shielding to the underside of the dash.)
Keep adding shielding until either you are satisfied with the results, or you find that adding more shielding does not yield any further decrease in readings.
Refine the shapes of the shielding pieces by trimming and bending. You can number them with a marker or tape to help you remember where they go. Take up carpeting if possible and lay the shielding in its final position. Fasten it securely. Use screws, pop rivets, tape, glue or any other mechanism you can think of to keep the shielding material in place. In this case, we were able to achieve an 84% reduction (1.47-0.25 / 7.61-0.25 = 16% field remaining).
What is the best way to shield magnetic fields from wiring?
First, let's understand that the magnetic fields from a single conductor wire emanate from that wire in a pattern that could be described as concentric cylinders. The image at right represents a cross section view of a current carrying wire. Notice the concentric circles of magnetic field lines around the wire. Notice also, that the magnetic field lines are more concentrated near the wire, and less concentrated as the distance to the wire increases.
Now, understanding that magnetic shielding "works" because it is a better "conductor" of magnetic field lines than air or just about any other material, let's see what happens with 2 different shield designs. First, let's make a shielding cylinder around the wire. In the cross section image at right, we see that the magnetic field lines that would have occurred at the radius of the shield will exist INSIDE the shield. However, magnetic field lines at all other radii will not be affected. Net effect: no shielding.
But what happens if we use a flat shield? As you can see from the image below, the magnetic field lines which intersect the flat shield will be compressed into the shield, leaving less magnetic field on either side of the flat shield.
But also, note the following:
If the edges of the shield are bent slightly TOWARDS the source, the high field area at the edge of the shield will move further away from the "shielded area".
In conclusion, for net current, flat (or nearly flat) shielding is more effective for fields from wiring in the area adjacent to the shield. The wider the shield, the larger the shielded area. Here you can download an excellent article on magnetic shielding principles. Contact us if you have specific questions about your shield design.
For situations where you have balanced current (that is equal current in the hot and neutral wires), a cylindrical shield can be effective. Take a look at this 13 minute video from Michael Neuert which demonstrates this phenomenon:
What is the safe distance for people from powerlines?
The sad short answer is: there is no such thing as a safe distance.
Here are the reasons:
What can I do (short of moving and saddling some other poor person with this problem) to reduce my exposure to a powerline outside my window?
In general, there are 5 ways to reduce your exposure to magnetic fields:
When it comes to powerlines, the options are limited as you do not have control over the powerlines themselves. The first step should always be to record readings of the magnetic field strength over a period of a few days using a reliable AC Gaussmeter to find out if you truly have a problem. Remember that the field will vary according to how much current (not the voltage) if being carried by the powerline. Also, remember that the only relevant readings are those taken where people actually spend time. High readings up close to the powerline are meaningless if the field inside your house is low.
Armed with this documentation, your next step should be to contact the utility company that owns the powerlines. Explain your concern and ask for their help in reducing your exposure. If the utility company wants to, they can do several things to lower your exposure:
Should you fail to get assistance for the power company (likely), you may be tempted to consider shielding. Naturally, the most effective shielding approach would be to shield the wires. Unfortunately, this is also impossible as the power company would never permit it. Shielding your home is possible, but not very practical. To achieve a reasonable degree of shielding, you would have to create a metal vault around your house, using thick metal plates with no windows. It would also be very expensive. Placing magnetic shielding material around your body is possible, but again not very practical.
Moving your house further back from the powerlines may be an option, but certainly not a very easy one. Make sure you carefully survey every proposed location for your house to make sure the fields are actually sufficiently lower at the new location that you are considering. Selling your home and moving to another location also comes under this heading. Make sure to use your gaussmeter to survey all homes you are considering, to avoid jumping from the frying pan into the fire.
Finally, there is the possibility of installing an active cancellation system. This is a device which constantly monitors the incoming field and produces an equal and opposite cancellation field. While it is not a do-it-yourself project, it may actually be your most practical solution. For each active cancellation system, an engineer must visit your location and custom design and install a system that takes into account the size, location, and strength of the offending source(s) and the dimensions of the area you want protected. Costs can vary from $10,000 to $50,000 or more. If this option appeals to you, contact us. We will be happy to answer your questions and refer you to a qualified engineer.
What brand of TV or computer monitor is best?
Our experience in measuring monitors of all kinds is that one cannot make generalizations about which type or which brand has higher or lower emissions.
A few years ago, we took our meters to a large electronics store to try to settle this question. We measured dozens of different types of TVs and monitors, including CRT, LCD, and plasma. Some where high, some were low. Some were high on E but not M, some were high on M but not E. Size had no correlation either. We found one unit which was the lowest on both. It was a Motorola product. The display model had a black bezel (plastic frame), but we wanted the gray one so we took a boxed unit OF THE SAME MODEL, but with gray bezel. When we got it back to the office, we set it up and tested again. It was worse than the worst unit in the store!!
Furthermore, a few months later, we went back and found that almost all the units available were different models.
From this, we have learned:
How do I shield my home from cell tower (or RF) radiation?
Compared to magnetic field shielding, shielding a home from cell tower radiation is reasonably straightforward. In theory, you want to create a continuous, highly conductive enclosure around the home. Any areas that are not conductive, even cracks under a door, will allow radiation to leak in. Perfect total shielding requires a perfect total enclosure. However, in a home environment, total radiation elimination may not be required. For example, perhaps 90% reduction is adequate.
There are several materials you can use to create the conductive enclosure, depending on your needs and your budget. Some materials are more appropriate for walls and ceilings, while other are better for windows. The higher the conductivity of the material, the better the shielding it will provide. Keep in mind such additional factors such as: durability, corrosion resistance, toxicity, ease of installation, appearance, and size.
For doors, walls, floors and ceilings, CuPro-Cote® or Y-shield conductive paints offer very good shielding and are very convenient. Apply like ordinary paint on interior surfaces. You can paint over the conductive paint with a standard latex paint to achieve the desired color and to protect the conductive surface.
You can also cover the walls with a conductive fabric such as Pure Copper Polyester Taffeta or ArgenMesh. Apply the fabric as you would a wallpaper, remembering to overlap slightly at the seams to avoid leakage. You can cover over the fabric with a standard wallpaper, paneling or drywall.
Remember to treat openings such as switch plates, outlet covers, dryer vents etc. But because shielding materials are conductive, be very careful to avoid allowing them to come into contact with electric wires to avoid a shock hazard. Also remember to provide proper grounding to each component which is not in contact with the others.
I used an RF shielding product which claims 80 dB attenuation at 2.4 GHz. Why am I only seeing 20 dB?
There is only one important 1 key to successful RF shielding: control leakage.
Remember that the attenuation spec for a shielding material is how much radiation penetrates through the shield. Let’s look at an analogy:
In many ways, RF behaves much like visible light, and RF shielding materials behave much like two sided mirrors. Image that you are outdoors on a sunny day. You set a large mirror on a stand above your head. The attenuation specification for the mirror is very high, perhaps 120 dB or more, so basically no light comes through the mirror. If leakage was not an issue, you would be in total darkness. We all know this is not the case. Leakage from the sides easily illuminates the shaded area. Granted, the amount of illumination is less than standing in full sunlight, but the attenuation is no where near 120 dB. Maybe more like 20 dB. Furthermore, using a shield with even better attenuation will not yield any more benefit.
Now imagine you are in a small room with only one window. Bright sunlight comes in the window and illuminates the room. When you place your mirror shield over the window, you get a dramatic attenuation of the light. But the extent to which leakage of light occurs around the perimeter determines how far from total darkness you will achieve in the room. We have all experienced this when trying to draw a curtain over a bedroom window. You must control the leakage to get it really dark. There is nothing wrong with the shield, light is leaking around the shield.
Because RF shields are reflective on both sides, radiation which does leak in will be reflected by the inner surface of the shield, effectively amplifying the amount of radiation in the room. Even the tiniest leakage at a seam can reduce attenuation by many dB. The obvious solution is to pay serious attention to leakage points. A great how-to book is available which describes materials and methods for controlling leakage in detail.
Why is it so difficult to shield a cellphone signal?
There are several ways to interpret this question.
First, let's look at it from the perspective of the cellphone owner:
Now, what's so hard about blocking a cell phone signal completely?
1- Therefore your shielding materials must provide very high attenuation levels. Typically, 100 dB or more shielding materials are required. Think about this way analogy: when you put sunglasses on the amount of light entering your eyes might be reduced by 90%, but you can still easily see where you are going. To block your vision completely, you would need a much higher level of reduction.
2- You must control leakage point VERY carefully. Gaps under doors, joints between shield sections, and even pinholes from sewing shielding material can permit these high frequency signals to penetrate. You need to create a "complete" enclosure. Any part that is not shielded is a leakage point.
A small pouch is not that difficult to make with the proper material. Shielding a whole house, or even a whole room is a more difficult challenge... if you want to completely kill the signal.
How do I measure the radiation from my cell phone?
This is perhaps the trickiest measurement you are likely to attempt. The reasons include:
There are NEAR FIELD probes which can be connected to a spectrum analyzer for a cost of $30,000 or more. And of course, there are $100,000 SAR machines for doing SAR testing. But what can an ordinary person use to measure the output from his phone or check the effectiveness of a shield?
We recommend the 6 GHz RF Meter with Near Field Probe accessory. For about $240, you can use this NEAR FIELD meter to check all surfaces of your phone and establish where the hot spots are.
I have speakers near my TV (or computer monitor) that are causing distortion (jitter) to the image. How can I shield these speakers?
Conventional speakers incorporate both a permanent magnet and an AC magnetic field to produce sound. The field from the permanent magnet is present whether the speaker is active or not. The AC magnetic field is only present when the speaker is activated, and varies in frequency and strength with the pitch and volume of the sound produced. The magnetic field from the two sources can deflect the electron beam in a cathode ray tube monitor (TV) causing distortion of the image, sometimes called jitter (and possible damage to the equipment).
You will have to use magnetic shielding alloys to shield these magnetic fields and you have a choice of several methods. Keep in mind that with magnetic fields, you can either shield the source of the offending field, or shield the thing(s) that you wish to protect.
1] Method for maximum aesthetics
To achieve maximum aesthetics you will need to be able to open the speaker cabinet and get access to the back of each speaker. There, you will find a donut shaped magnet, proportional in size to the size of the speaker, over which you will place a cup shaped shield.
Because you will be placing the shielding material in close proximity to this strong magnetic field, you will have to take saturation into account. This means using at least 2 layers of shielding.
For the layers closest to the magnet, choose a high saturation material such as MagnetShield. This material has the ability to "absorb" the initial blast of the field without saturating and becoming useless, but it will only give a limited attenuation. It is very low cost, so 2 or 3 layers are practical.
The outermost layer should be a high permeability material such as Joint-Shield. This outer layer will "absorb" much of the field which has evaded the first layer and yield a very high degree of attenuation. Note that attenuation will be greatest close to the speaker magnet, where the field is strongest (most interfering) anyway.
MagnetShield and Joint-Shield are both offered in a convenient 4 inch wide strip. The material is thick enough to provide good shielding, but still can be cut with a scissors and shaped by hand. For especially strong magnets, you may need more than one layer of each material.
Here is how you do it:
Wrap the MagnetShield around the speaker magnet (notice that it is attracted to the magnet) in a cylinder shape. Cut it so that you have about 1" of overlap at the seam. Use duct tape to tape the seam securely. Cut the material which extends backward at several locations so you can bend these "tabs" inward to form the "bottom of the cup" shape. Leave this layer in place.
Joint-Shield is provided with a peel-and-stick adhesive on one side. Before removing the adhesive backing, cut and shape the material just like the first layer, but on top of the first layer. Remove the adhesive backing and press the second layer onto the first layer. You are done!
Just be careful not to disturb or allow the shield to touch the electrical contacts on the speaker.
2] The Quick and Easy Way (and Maximum Field Reduction!)
If you need maximum field reduction, or cannot open the speaker cabinet, or you simply want to take the easy route, you can simply place flat magnetic shielding alloy between the speaker and the TV.
The magnetic fields at the side of the speaker magnet have different characteristics compared to at the back of the magnet, and different shielding materials are required. Take this into account when considering where your speakers will be positioned relative to the TV.
Shielding the side of the speaker:
Shielding the back of the speaker:
3] The Third Alternative
You can always place the TV or monitor inside a shielded enclosure. This will protect the monitor from external fields produced by the speakers and any other sources.
How can I shield my laptop?
The most direct way to reduce your exposure from a laptop is to increase your distance from the device. Use a wired remote keyboard and mouse (not the wireless type!!) and place the laptop as far away as you can while still being able to view the screen. You can increase the text size on the screen if needed.
Laptops usually produce three types of electromagnetic fields: Radiofrequency (wifi), AC electric fields and AC magnetic fields. You can either shield the laptop (source) or shield yourself.
To shield the electric fields and wifi from the laptop screen, use a Computer Monitor Shield to cover the screen. Be sure to connect the ground cord. Covering the keyboard area of the laptop with a shielding fabric such as High Performance Silver Mesh will reduce electric fields from these areas while still allowing you to see the keyboard.
Why can't I just use lead or copper or aluminum foil for magnetic shielding?
In the strictest sense, magnetic shielding is not truly shielding at all. Unlike the way a lead shield stops X-rays, magnetic shielding materials create an area of lower magnetic field in their vicinity by attracting the magnetic field lines to themselves. The physical property which allows them to do this is called "permeability".
Unlike X-rays, sound, light or bullets, magnetic field lines must travel from the North pole of the source and return to the South pole. Under usual circumstances, they will travel through air, which by definition has a permeability of "1". But if a material with a higher permeability is nearby, the magnetic field lines, efficient creatures that they are, will travel the path of least resistance (through the higher permeability material), leaving less magnetic field in the surrounding air.
Air ........... 1
Nickel .................. 100
Now it is easier to see why a magnetic shield in the shape of an enclosure (sphere, box, tube, etc.) offers much better shielding than a flat shape or partial enclosure. A source within the shield will produce field lines which will travel through the air immediately surrounding the North pole until they reach the shield. Then traveling through the shield, they will emerge into the air surrounding the South pole and back to the source. Traveling through the low permeability air outside the shield does not offer any efficiency advantage! (Notice that the diagram to the right is a cut-away view of a tube shaped shield.)
Similarly, if the source of the field is outside of the enclosure, the magnetic field lines will travel through the material of the enclosure on their way back to the source, never finding it more efficient to permeate the air space inside the enclosure. For these reasons, enclosing either the source of the field, or the thing(s) that you wish to protect from the field, offers the most effective use of the shielding material, and is usually the most cost efficient as well!
An important consideration when shielding magnets is that the magnets will be attracted to the shielding material. There are no magnetic shielding materials that will not be attracted to a magnet.
Shielding repulsion between 2 magnets is easy:
Shielding attraction between 2 magnets requires that each magnet have its own shield. The shield does not need to be in contact with its respective magnet, but it must be held fixed in position relative to its magnet. Again, the proper number of layers will depend on the strength of the magnets, the distance between them, and the size and shape of the shield. Simply add one layer at a time until the two magnets drop away from eachother.
Finally, a word about shielding just one pole of a magnet:
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