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This mate­r­ial is intended for edu­ca­tion pur­poses only

Cap for EMF pro­tec­tion (ideal mate­r­ial)

There are lot of clothes in mar­ket to pro­tect sen­si­tive humans from elec­tro­mag­netic fields (EMF). Do they work? As I am not elec­tro­mag­netic field sen­si­tive and I am not good enough sit­u­ated to buy and test these clothes, I can­not answer this ques­tion for sure with 100% cer­tainty.

As the­o­ret­i­cal sci­en­tist and elec­tro­mag­netic com­pat­i­bil­ity engi­neer (EMC) involved in test­ing of shield­ing mate­ri­als, mea­sure­ments of elec­tro­mag­netic devices, 3D mod­el­ling of com­plex elec­tro­mag­netic sit­u­a­tions, I’ve knowl­edge to mea­sure and model. In this case, to eval­u­ate cap it is nec­es­sary to have cou­ple of them for mea­sure­ments. None of EMF clothes man­u­fac­tur­ers and sell­ers wanted to con­tribute to this arti­cle by lend­ing some caps for mea­sure­ments and tests. And it is under­stand­able– not all the facts writ­ten in item char­ac­ter­i­za­tion is true.

I’m not here to expose or crit­i­cize play­ers in elec­tro­mag­netic field (EMF) pro­tec­tion. I’m curi­ous by myself– can cap made of spe­cial con­duc­tive tex­tiles pro­tect humans. I’m using 3D elec­tro­mag­netic mod­el­ling to answer this ques­tion. Some val­i­da­tion is car­ried out in to ver­ify that mod­el­ling will give cor­rect results. Mod­el­ling will be car­ried out using ideal shield­ing mate­r­ial for cap (per­fect elec­tric con­duc­tor) not a mate­r­ial that is used in real life (con­duc­tive cloth that is far from ideal shield­ing mate­r­ial– link) as it takes con­sid­er­able less com­put­ing power. If cap made out of ideal shield­ing mate­r­ial can help to pro­tect from elec­tro­mag­netic fields, then fur­ther research can be car­ried out with real life mate­ri­als– tex­tiles.

Cap cov­ers the head and it obvi­ously is used to pro­tect the most impor­tant organ in human body– brain. Spe­cific Absorp­tion Rate (SAR) will be used for eval­u­a­tion. Max­i­mum Spe­cific Absorp­tion Rate (SAR) will be mod­elled sep­a­rately for brain, back brain and body mus­cles.

SAR (spe­cific absorp­tion rate) is an indi­ca­tion of the amount of radi­a­tion that is absorbed into a head whilst using exposed by elec­tro­mag­netic fields, the higher the SAR rat­ing the more radi­a­tion that is absorbed into the head. A SAR value is a mea­sure of the max­i­mum energy absorbed by a unit of mass of exposed tis­sue of a per­son in elec­tro­mag­netic field, over a given time or more sim­ply the power absorbed per unit mass. SAR val­ues are usu­ally expressed in units of watts per kilo­gram (W/​kg) in either 1g or 10g of tis­sue.

Also elec­tro­mag­netic field strength will be mod­elled in brain to see what are the elec­tro­mag­netic field val­ues in brain with and with­out cap.

An elec­tro­mag­netic field (also EM field) is a phys­i­cal field pro­duced by elec­tri­cally charged objects. It affects the behav­ior of charged objects in the vicin­ity of the field. The elec­tro­mag­netic field extends indef­i­nitely through­out space and describes the elec­tro­mag­netic inter­ac­tion. It is one of the four fun­da­men­tal forces of nature (the oth­ers are grav­i­ta­tion, weak inter­ac­tion and strong inter­ac­tion).

Source of the elec­tro­mag­netic field will be located:
1. Above human model (sit­u­a­tion when elec­tro­mag­netic field (EMF) source is located above per­son– roof anten­nas, anten­nas in plane fuse­lage, anten­nas on upper floors, etc.);
2. Below human model; (sit­u­a­tion when elec­tro­mag­netic field (EMF) source is located below per­son– anten­nas in plane floor, anten­nas on lower floors, etc.);
3. In front of human model;
4. Behind human model;
5. On left of human model;
6. On right of human model;

Eval­u­a­tion will be car­ried out at three fre­quen­cies 433MHz, 900MHz, 2.4GHz.
433MHz is a UHF band in which licence free com­mu­ni­ca­tion devices are allowed to oper­ate. Many wire­less devices are oper­at­ing in this range.
900MHz is UHF radio spec­trum inter­na­tion­ally allo­cated to ama­teur radio on a sec­ondary basis. This is one of most pop­u­lar fre­quen­cies for cel­lu­lar phones.
2.4GHz Wi-​Fi net­works, Blue­tooth, Zig­Bee, car alarms, microwave ovens.

In Fig. 1. human body with and with­out cap is rep­re­sented. Mod­el­ling envi­ron­ment with elec­tro­mag­netic field is shown in Fig.2. In this case, plane wave (red plane) is located in front of human body and it is hor­i­zon­tally polarised. Human body tis­sues– brain, back brain, body mus­cles are mod­elled with real tis­sue elec­tro­mag­netic para­me­ters as defined in “COM­PI­LA­TION OF THE DIELEC­TRIC PROP­ER­TIES OF BODY TIS­SUES AT RF AND MICROWAVE FRE­QUEN­CIES” by Camelia Gabriel in the U.S. Air Force Report AFOSR-​TR-​96.

Fig. 1. Human body with and with­out cap

Fig. 2. Human body in mod­el­ling domain with plane wave (red) in front

900MHz elec­tro­mag­netic field mod­el­ling with human body with cap is given in Fig. 3. Elec­tro­mag­netic field source is in front of human. Zoomed head with cap is shown in Fig.4. As can be seen elec­tric field strength on cap sur­face is very high. Brain is zoomed in Fig.5. for the same sit­u­a­tion.

Fig. 3. 900MHz elec­tro­mag­netic field and human body


Fig. 4. 900MHz elec­tro­mag­netic field and human body, head zoomed

Fig. 5. 900MHz elec­tro­mag­netic field and human body, brain zoomed

In Fig.6. elec­tro­mag­netic field strength in brain is analysed and most exposed sur­faces can be located.

Fig. 6. 900MHz elec­tro­mag­netic field in human brain


SAR results (spe­cific absorp­tion rate)
SAR results are sum­marised in Table 1. “Ideal mate­r­ial” cap the best brain pro­tec­tion offers if source of elec­tro­mag­netic wave is located on the left or on the right of your head exceed­ing 80% of SAR reduc­tion for all three analysed fre­quen­cies– 430MHz, 900MHz, 2.4GHz. If elec­tro­mag­netic field source is located above the head SAR reduc­tion (brain pro­tec­tion by cap) varies by the fre­quency– at 433MHz it is only 26%, at 900MHz it is 76% and at 2.4GHz it reaches 86%. In case if elec­tro­mag­netic field source is located in front of you, absorp­tion rate will decrease by only 5% at 433MHz, decrease by 15% at 900MHz, decrease by 62% at 2.4GHz. In case if elec­tro­mag­netic field source is located in behind you, absorp­tion rate will decrease by only 46% at 433MHz, decrease by 68% at 900MHz, decrease by 80% at 2.4GHz. SAR val­ues are increased– brain receives more elec­tro­mag­netic field– in case if source of elec­tro­mag­netic fields is located below the human body (if you are on roof or tower and anten­nas are located below you, or if you are in your flat and your neigh­bour below you have ). At 900MHz SAR increases by 14%, and at 430MHz it increases by 23%. SAR results in Table 1 are marked in red if SAR is increas­ing due to cap usage.

Elec­tro­mag­netic field results
These results are cor­re­lated to SAR results as field is the energy source that heats up the brain. Elec­tro­mag­netic field results are sum­marised in Table 2. “Ideal mate­r­ial” cap the best field atten­u­a­tion offers if source of elec­tro­mag­netic wave is located on the left or on the right of your head. At 433MHz reduc­tion is only 7dB, at 900MHz reduc­tion is only 6dB and at 2.4GHz elec­tro­mag­netic field reduc­tion is 1dB. Fur­ther analy­sis is not car­ried out as elec­tro­mag­netic field reduc­tion is less than few dB. Few dB atten­u­a­tion for elec­tro­mag­netic field offers very low pro­tec­tion, if com­pared to shielded elec­tro­mag­netic rooms that offer more than 120dB atten­u­a­tion. SAR results in Table 2 are marked in red if SAR is increas­ing due to cap usage.

Results in short and in sim­ple lan­guage
Cap effec­tive­ness (use­ful­ness) depends on elec­tro­mag­netic field source fre­quency and loca­tion (and mate­r­ial– not analysed in this arti­cle). Cap can reduce elec­tro­mag­netic fields in your brain and increase fields in your brain.
If cap is made out of ideal shield­ing mate­r­ial or alu­minium, cop­per foil, it will reduce heat­ing up your brain by 80%, if elec­tro­mag­netic field source is located on left or on the right of you. If field source is located in front, back or above head, heat­ing reduc­tion will be at least 26%. If source of elec­tro­mag­netic field is located below you, brain will be heated up by up to 23%. In Table 1 and Table 2 results are marked red if cap increases elec­tro­mag­netic effects on brain.



Table 1 Energy absorb­tion reduction/​gain in human brain if “Ideal material“cap is used



Table 2. Elec­tro­mag­netic field reduction/​gain in human brain if “Ideal material“cap is used


Visu­al­i­sa­tion
Visu­al­i­sa­tion of human brain is pre­sented, to take a look how elec­tro­mag­netic field is prop­a­gat­ing inside the head. Elec­tro­mag­netic field source is located above the human body.


Model with and with­out cap. Cap is made out of per­fet material.


433MHz prop­a­gat­ing in human brain. Cap offers no pro­tec­tion at this fre­quency, if wave is located above the head.
Elec­tro­mag­netic field is amli­fied at some areas due to res­o­nances in cap. Max­i­mum field value increases by 1dB.


900MHz prop­a­gat­ing in human brain. Cap offers poor pro­tec­tion at this fre­quency, if wave is located above the head.
Elec­tro­mag­netic field is atten­u­ated by 6dB

2.4GHz prop­a­gat­ing in human brain. Cap offers poor pro­tec­tion at this fre­quency, if wave is located above the head.
Elec­tro­mag­netic field is atten­u­ated by only 4dB


433MHz prop­a­gat­ing in human brain. Cap offers no pro­tec­tion at this fre­quency, if wave is located above the head. Elec­tro­mag­netic field is amli­fied at some areas due to res­o­nances in cap. Max­i­mum field value increases by 1dB.


900MHz prop­a­gat­ing in human brain. Cap offers poor pro­tec­tion at this fre­quency, if wave is located above the head. Elec­tro­mag­netic field is atten­u­ated by 6dB


2.4GHz prop­a­gat­ing in human brain. Cap offers poor pro­tec­tion at this fre­quency, if wave is located above the head. Elec­tro­mag­netic field is atten­u­ated by only 4dB

This mate­r­ial is intended for edu­ca­tion pur­poses only

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