Monday, 28 March 2011

Why do electric appliances emit electromagnetic radiation?

Electric appliances make our life easier and simple. 50 years ago there was a saying "more electricity less work to do". Electric home appliances do our hard work, entertain us, heat our food, heat the house at winter and cool it in the summer. Electric home appliances help us do every task and chore very easily and faster. But all electric appliances emit electromagnetic radiation in low frequency (eclectic network frequency) and some also in high frequency (cordless phones, Wi-Fi router, laptop, microwave ovens).  We need to know when and why these appliances emit electromagnetic radiation. We need to keep safe distance and to find ways to limit and to avoid unnecessary exposure to electromagnetic radiation.

Electromagnetic field is created around every electric conductor (a metallic wire for example) when an electric current is running through it. As higher the current is the higher the electromagnetic radiation will be.  The frequency of the electric current will be the frequency of the electromagnetic radiation, usually at the same frequency of the electric network at around 50 or 60 Hrz. The levels of electromagnetic radiation in low frequencies drops as you move away from the source.

In electric appliances, there are a lot of wires, electronic components, electronic board and power convertors. When the device is turned on, and in some of the cases even when turned off, those components and wires emit electromagnetic radiation in the frequency of the electric network (mainly).
It is important to remember that low frequency radiation passes easily thought walls. Therefore the location of the home appliances in the house is very important. If located wrongly people living in the house can be exposed to high levels of electromagnetic radiation.

Electromagnetic radiation emitted from electric appliances in standby mode.

Most home appliances emit electromagnetic radiation in low frequencies and uses electricity even when they are connected to the electricity network and turned off (standby mode). The way to reduce the electromagnetic radiation and the electric waist is to cut the power supply off. In order to do that you need to unplug your devices from the electric socket when not in use. This operation is both not easy and can be dangerous since you increase your chances of getting electrified. A multi socket with a power switch allows you to switch off the power supply to all the devices connected to it, easily and with no risk. A multi socket with a power switch is not very expensive (~US$10) and installing it is very easy. In this way you can easily save some electricity and also reduce the electromagnetic radiation emitted from the home appliances while in standby mode. Cutting off the power supply of home appliances in standby mode can also protect them from power bursts and lightning strikes.

Electromagnetic radiation from voltage transformers

Two types of voltage transformers are available today in the market, classic and electronic. The classic voltage transformer is based on two coils raped against a magnetic core. The ratio between the two coils is the ratio between the input voltage and the output voltage. The electronic voltage transformer consists on several small coils, capacitors, electronic parts and an electronic board.

The classical voltage transformer way of work is fully based on electromagnetic fields and while operating it emits high levels of electromagnetic radiation in the frequency of the input voltage. In most cases an electric voltage transformer emits less electromagnetic radiation than a classical voltage transformer.
The higher the current that flows via the voltage transformer wires, the higher the radiation it emits. It is recommended to keep a safe distance of one meter away from a classical voltage transformer and a half meter away from an electronic voltage transformer.

 Electronic voltage transfromersElectromagnetic radiation from electronic voltage transfromer 

Electromagnetic radiation from electric motors

An electric motor is based on the principle of magnetic fields. In all electric motors you will find magnetic core and coils. Every Electric motor emits electromagnetic radiation. The radiation levels are higher when the motor power and load are higher. You can find electric motors in every home, office and factory. You can find electric motors in a refrigerator, air-conditioning systems, an aquarium and ponds filters, air pumps, fans, washing machines, sewing machines and lots of other every day home appliances.

You can find a small electric motor even in clocks (analog), and around it you there will be an electromagnetic radiation field that can be measured by a very simple meter.
From a home used electric motor it is best to keep one meter of safety distance. In industrial motors you better keep more safety distance, or try to install some electromagnetic radiation shielding since their working current and the radiation they emit can be a very high (much higher than most home electric motors).
 Air condition Electric motor in Air Fan

Electromagnetic radiation from CRT, LCD plasma and LED screens and TVs

CRT - TV and screen based on a Cathode-Ray Tube.

There is a wide variety of television in today market and households.  Televisions and screens that are based on Cathode-ray Tube (CRT), the big, clumsy round and heavy devices, are the oldest type of TVs and they emit the highest levels of electromagnetic radiation (compared to other types of TVs and to other radiation sources in the house). The reason is that these TVs work on the principle of a variable electromagnetic field generated around the screen used to change the projection of the electrons making their way from the electronic booster/canon on the back of the tube to the Fluorescent screen. This field surrounds the screen on all sides. At the front of an old CRT screen there is a protective layer that blocks some of the radiation. Therefore on the back and sides (where there is no protection) the radiation levels are the highest. Since the low frequency electromagnetic radiation can pass through walls, a common mistake is to place a bed next to the other side of that wall where a CRT-TV is placed at. In a CRT TV some levels of electromagnetic radiation will be emitted even on standby mode.

In order to save office space, many businesses and offices, place computer tables against each other, back to back, which means that also the computer screens are placed back to back. In this situation, workers are exposed to high levels of electromagnetic radiation from the rear  and sides of the CRT screens.
Safety distance from a 29" CRT TVs is at least 2 meters from all sides. A safety distance from a 19" CRT PC screen should be around half a meter in any direction.

 CRT TVElectromagnetic radiation from 29" CRT TV

Electromagnetic radiation from 14" CRT TV 

LED/LCD and Plasma TVs

LCD, plasma and LED screens and televisions work in a digital method and are not based on a magnetic principle. Therefore the radiation levels that are emitted from all sides, are very low compared to a CRT TV or screen. The sources of radiation in these monitors are computerized circuits, microprocessors and power supplies that are located on the electronic circuit board on the back on the screen. Since the radiation levels from LCD/LED and plasma screens are usually very low, the safety distance from LCD/LED and plasma screens is only half a meter.

Plasma screens and TV are also a source of electric pollution (it produces an electrical noise that is added on to the electrical grid at home) but the levels of low frequency electromagnetic radiation emitted from the plasma screens are similar to the levels emitted from LCD and LED screens.
Safety distance from LCD screens, plasma TV LED is half a meter in any direction

Electromagnetic radiation from 19" LCD TV 40" LCD TV

Radiation form microwave ovens

The microwave oven can be found in almost every kitchen in the modern world. Microwave ovens use the heating effect of electromagnetic radiation (in the frequency of water molecules) to heat the fluid in the food and, by that, to heat the food itself. The frequency used in microwave is around 2.4 GHz and it is similar to the frequencies used for communication, cellular and DECT phone. When a microwave oven is on, part of the radiation goes through the protection shield-filter, that is part of the microwave oven door, and spread into the room. The part of the radiation that escapes from the oven is relatively small, and can't cook our body during the short time it is on, but it is definitely not recommended to look into the oven for several seconds (possible damage to the eye protein) or even stay in the kitchen when the microwave oven is on.

Just for comparison, In Israel when a radiation tester tests a microwave oven, the oven will be considered "safe to use" if at a distance of five centimeters from the door the tester will measure radiation level of 5000 micro watts per square centimeters (the Israeli standard, which is very high, for cellular antenna radiation level is about 42 micro watts square centimeters.
In addition, microwave oven, like most electrical appliances, emits low frequency electromagnetic radiation in the electrical network frequency of 50 Hz. This low frequency radiation is emitted all the time the microwave oven is connected to the electricity network. The microwave oven, low and high frequency, electromagnetic radiation emission must be taken into account when deciding about the device location in the house (not near people) and it is recommended to pull it out of the electric supply when not in use.

Low frequency Electromagnetic radiation from a microwave ovenMicrowave oven
High frequency Electromagnetic radiation from a microwave oven

Using a mobile phone

I think that using a mobile phone should be limited to only short "must" or "emergency" calls. Using a mobile phone exposes you, people around you and people who are in the vicinity of the mobile phone masts to electromagnetic radiation (both RF and ELF), so I think that limiting the time you use the mobile phone is a smart thing to do. However sometimes you have to use the mobile phone, to call the police, to ask for help, to say you are late, to ask for directions. I suggest that you should try to reduce your exposure to electromagnetic radiation as much as possible, while using the mobile phone. Even if you use the mobile phone once in a while, I still suggest you to try and limit your exposure to the electromagnetic radiation from your mobile phone.

Electromagnetic radiation from mobile phones

When talking on the mobile phone, the mobile phone emits changing levels of electromagnetic radiation (High frequency RF single). In addition the cell phone emits also low frequencies EMR created in his electronic parts, boards and as created in the processes of the RF signle transmission . The levels are dropping as you move away from the device. The most sensitive part of the body, to electromagnetic radiation, is considered by many to be the head. I think that other parts of the body might also be very sensitive to electromagnetic radiation. The first thing I feel when I am exposed to electromagnetic radiation is a headache but this does not say that only the head is affected.  Having said that I would suggest not to put the mobile phone next to your head while talking but I would also suggest not to put it in your pockets or in your belt clip, try to stay as far as possible from it at all times especially when making a call and during conversations.

Limit your exposure

So what can you do if you do want or need to use the mobile phone but still want to limit your exposure to electromagnetic radiation? I think the best thing to do is to use AIR TUBE earphone or the speaker mode and hold your mobile phone as far away as possible from your head and body. If you use the speaker phone or AIR tube and the mobile phone is still next to your body, head, on your belt clip or in your pocket you still get exposed to electromagnetic radiation. You need to remember to keep distance from the mobile phone as much as possible while it is emitting electromagnetic radiation.

Speaker phone

Most of today mobile phones have a speaker option, and together with holding the mobile phone far from your head and body, using it will limit your exposure to electromagnetic radiation emitted by your mobile phone (both high frequencies and low frequencies).  But sometime you can't use the speaker phone option, like when there is a lot of ambient noise, when you don't want other people to be disturbed by the conversation and some other reasons.

Using a regular earphone

Using regular earphone allows you to hear and to be heard better than when using a speaker phone while reducing your exposure to electromagnetic radiation since the mobile phone is no longer next to your head (the far it is the less electromagnetic radiation is getting to you). But some of the high frequency electromagnetic radiation makes it's way on the earphone wire to your head.

Air Tube earphone
Using an Air Tube earphone allows you to hear and to be heard better than when using a speaker phone while reducing your exposure to electromagnetic radiation. In a regular wired earphone some of the high frequency electromagnetic radiation makes it way on to the earphone wire and to your head. When using an Air Tube wired earphone most of this radiation does not reach the ear or head. In an Air Tube wired earphones, the wire goes up as far as 20 cm from the head. It has 2 speakers and a microphone and the sound from the speakers is making its way to the ear via one or two air tubes which can pass air waves and sound but do not carry electromagnetic radiation. In an Air Tube earphone some of the electromagnetic radiation makes its way onto the wire but not to the head since there are no metal wires coming up to the head. You still have to keep the mobile phone as far as possible from your body, and the long wire of the Air tube earphone allows you to do so.

My experience

When I must use the mobile phone I usually start to feel bad after several seconds (about 20 seconds) of using it against my ear. If I use a regular wired earphone the headache appears after a minute. Using the mobile phone speaker allows me to use the mobile phone for up to 2 minutes, depending on how far I can place the mobile phone (and still hear and be heard). When I use my wired air tube earphone I can talk for about 3-4 minutes until the first sign of a headache appears. In addition using the wired air tube earphones allows me to place the mobile phone far away from me and still hear and be heard.

First I did not believe that this wired air tube earphone is really working, that it is worth the money and that it is better than the ordinary wired earphone. But when I did some tests and measurements I noticed that most of the electromagnetic radiation that was making its way up the wire was "stopped" at the speakers and did not make its way to the user ear. Later on I tested it on myself several different occasions when I had to use the mobile phone, and was amazed as I did not feel the expected headache, even after a 3 minute call. Usually when I use a regular wired earphone I can use the mobile phone for only 1 minute before I feel the pain.  If I would (and when I used to) use the mobile phone and I put it next to my head the expected headache appeared after only 20 seconds.

Why not Bluetooth?
In the market today you can find many types of bluetooth and wireless earphone, some types even have air tubes. Using a bluetooth device exposes you to some additional electromagnetic radiation from the bluetooth device and from the mobile phone, in addition to the one emitted from your mobile phone when making a call. In addition people usually tend to keep their bluetooth device working all the time. Bluetooth devices and mobile phone with their bluetooth connection enabled emits electromagnetic radiation all the time.  I don't recommend using a bluetooth devices or earphones even when it comes with an Air Tube.

Official protocol of electromagnetic radiation testers in Israel

The official measurement protocol was created by the Israeli ministry of environment protection and all radiation testers in Israel are obligated to follow it. The environmental protection ministry supervise environmental sources of radiation like mobile phone towers and therefore this protocol is meant to measure these kind of sources (that are located in the environment) even when the measurement is done inside the house. The environmental protection ministry will allow the tester to step outside the protocol, if the customer requests it, but the outcomes of these measurements can't be included in the official report but only as an appendix. 

Protocol's instructions

High – all measurements should be taken at the height of one meter above the floor, in case there is an under floor heating it is allowed to measure 20 cm above the floor. 
Location – the tester must measure in four corners of the room, one meter from the walls and also at one point in the middle of the room. The tester can also measure radiation levels in more locations in the room but he is not obligated to do so. If the room is too small for several measurements, the test should measure only in the middle of it. 

Don't measure next to windows or radiation sources. 

The outcomes that appear in the official report are sometimes average calculations of the measurements that were done in the field. I think that this method does not give the whole picture and can cause, in some cases, disinformation especially when the costumer wants to identify the radiaiton sources inside and outside the house and in case he wants to understand where, when and what where the highest levels. 

Room background test 
When you need to test the electromagnetic radiation background levels inside a room you better start with the official protocol above. You need to stay one meter from the walls windows doors and radiation sources inside the room. This kind of measurement can show you the background levels inside the room. It is recommended to use an advanced electromagnetic radiation meter that gives a numeric indication of the radiation in all three axis, with fast sampling rate and with a clear and detailed display. A simple electromagnetic radiation meter can give you only a raw estimation of the levels. It is recommended to repeat this measurement twice, once with the radiation sources (cordless phones, WIFI routers, a CRT TV and etc) inside the house turned on and the second time when they are turned off. Analysis of these measurment outcomes can show you what the background radiation levels in the room are, and how the radiation sources affect these levels. If you want to understand the effect a single source has on the background levels in the room you can also repeat the test when only this source is turned on. 

Searching for radiation sources in a room:

All types of electromagnetic radiation meters, even the simplest ones, can be used for searching radiation sources in a room (the meter should be for the same type of electromagnetic radiation as the source emits, either high frequency-RF or low frequency). All you have to do is to scan the room step by step, meter by meter. Whenever the meter shows an increase in the radiation levels that means that you are getting close to a source. If the radiation levels are dropping you are getting away from the source. It is recommended to use a meter with voice indication that makes it easier to notice changes in the radiation levels without looking on the meter’s display. 

Scan key points: 
  1. Scan in the room 3 times, once on the floor, a second time at one meter high and then at the hight of a human being’s head. 
  2. The scan should include all the parts of the room. 
  3. Use a clear scanning pattern that was planned before the test started (from center to the walls, or from one side of the room to the other side. 

Searching for radiation source from other rooms

When searching for radiation sources outside the room we should focus on the border areas of the room with other spaces of the house (other rooms and floors) and with the outside, like walls, windows, doors, rooftops and underground spaces. 
When there is a high level radiation source outside the room, the first sign for that will be medium to high radiation background levels inside the room itself. 


  • When there is a high current electric wire inside the wall, the low frequency that is created around the wire will penetrate the room. If you scan the wall, verticaly and horizontaly, with a Low frequency electromagnetic meter the meter will show high radiation levels near the wire, and will enable you to expose the wire as the radiation source. 
  • In case there is a DECT base station next to the wall in the next room, the first signs will be medium to high levels of high frequency radiation inside the room. When the right wall will be scanned the radiation levels will increase as the meter will be closer to the DECT phone location, until it will reach the maximum measurement. 
  • In some cases when there is a radiation source in the next floor or in the floor below, there will be high radiation levels next to the ceiling or floor. 
  • When there is a high frequency radiation source outside the house, for example a mobile phone mast, the meter will show high levels of high frequency electromagnetic radiation mostly next to the window, and in some cases even on the wall which are in the direction of the mobile phone mast. 
  • When there is a low frequency radiation source in the near vicinity of the house (like an external electric power convertor or high voltage electric power wiring) you will be able to measure high levels of extreme low frequency electromagnetic radiation in parts of the rooms of the house which are close to it (low frequency electromagnetic radiation passes easily via walls). 
  • When there is a CRT TV on the other side of a wall you will be able to measure high levels of low frequency electromagnetic radiation in the room, the pick will be on the wall next to the location of the TV (on the other side). 
  • When there is an external radiation source outside the room that radiates in medium or low levels, for example a wifi router or a small power convertor, it will be difficult to locate the source by doing measurments in the room next door. In order to do so you will need to use a very sensitive and accurate advanced electromagnetic meter with a detailed display. In this case it is recommend taking a look inside the rooms next door in order to get some clues for the radiation source that can influence the measurement. 
 Sleeping bed. Low frequency radiation sources from the bed sides and from the next room are marked in red.
 Living room with an aquarium filter, a TV and some audio and video equipment. LFE radiation sources are marked in red. The radiation emitted reaches the next room (see pictures above).
Kitchen ELF source is marked in red.

Identify radiation sources outside the house.

In order to identify high frequency radiation sources outside the house you need to use a directional radiation meter (the meter should have a directional antenna). The trick is to hold the meter in front of you and to scan the 360 degrees around. When the meter will be directing to, or will be closer to a radiation source, the radiation levels will usually be higher than when the source is not in front of the meter or far away from it. 
If you are using a 3 axis meter it is best to configure the meter to measure only in the axis which is parallel to the axis of the radiation source (for example axis Y for mobile phone masts). 

Identifying low frequency radiation sources outside the house is trickier since low frequency electromagnetic radiation is less directional than the high frequency. The search for the source should be based on getting closer or going away from the radiation source while trying to look and guess where the low frequency radiation sources are located in the near vicinity.

Measuring radiation levels in places you stay in.

One of the most important measurements to be done inside a house is to measure the electromagnetic radiation levels in all the places in which you might stay in for a long time (more than 5 minutes). Examples for such locations in the house can be found in the following list: 
  • Sleeping Bed 
  • Home office station 
  • Kids Gaming-playing room 
  • Desk 
  • Dining Table 
  • Pc station 
  • Sofas
  • Sitting arraingement, sofa 
  • Living room 
The technique is to measure on top and next to the place in which the human body will be, and to try and understand what will be the radiation level and for how long the body will be exposed to it. In addition you need to try and figure out which radiation sources influence the radiation levels at this point. 
In the past I came across people who told me that they found a radiation source on their home working station desk, but they didn't think that it was serious since they sit next to it only for a short time. When I asked them for "how short?", they replied that they use it for half an hour to one hour each day. I just want to make it clear; I think that every exposure to electromagnetic radiation is not good and should be minimised as much as possible, and if possible to reduce it down to zero. Half an hour a day is not a short time as much as exposure to radiation is concerned, it is a lot of time. Whenever there is a radiation exposure it is highly recommended to try to find the source and turn it off so there will be no radiation emittion (no radiation for you :-)  ) . 

bed room


Home office room

Several ways to measure electromagnetic radiation

It is important to know the difference between the different types of Electromagnetic Radiation measurements. Every type of measurment will have a different focus, different methods and in some cases you should use different meters. The right meter should be chosen according to its charataristics and not only according to the frequency that it can measure. 

Electromagnetic radiation sources can be divided into 2 frequency types, low frequency (power line, power transformers) and high frequency (RF, DECT, Mobile phone, microwave). Some meters can measure both types, some can measure only one. 

Meters sampling rate 

When the radiation level is changing rapidly (like in some digital radiation sources like 3G and 2G mobile phones, WiFi routers and etc.) it is very important to use electromagnetic radiation meters with a high sampling rate. If the sampling rate is slow, for example once a second like in some simple meters, the measurement outcome of a WiFi router will be very low, when in reality it picks to high levels several times in a second. I usually use electromagnetic radiation meters with the highest possible sampling rate. 

Average measurements 

In some cases it is the custom to make an average out of the levels of radiation that were measured. It is recommended (but not a must) to make a note of the minimum and maximum values that were measured. When average outcomes are reported it will usually mean that the picture revealed by the report will be very partial and limited since the peaks and high values that happened in some of the time were averaged by low values that were measured most of the time. In most cases I don't average my measurements. I try to get a clear and full picture and try to understand what causes the high peak levels. 

Measuring over long periods of time 

When the Radiation levels are changing throughout the day there is a need to measure them during all the hours of the day, sometimes for several days. In most cases when this is the need you have to use electromagnetic radiation meters that has the option to monitor the radiation levels throught the day and night, and to store all the results in an internal memory, which can later be reviewed, examined and processed . The most recommended meters for this operation are meters that can be connected to a PC for data acquisition, extraction, realtime and offline analysis and display of all the information gathered during the measurement.