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Electromagnetic Fields
Electromagnetic fields are characterized by the following:
Electric and magnetic fields are interconnected, but are two different aspects of the same phenomenon. Wherever there is electricity, both appear – both electric field and magnetic field. The two must both be separated in the working environment as their influential mechanism differs and distinct maximum tolerances have been established for both.
Table. The differences and similarities of electric and magnetic fields.
Electric Field |
Magnetic Field |
unit of measurement: volt per meter (V/m) |
unit of measurement: Tesla (T) |
relatively easy to screen |
penetrates almost everything; hard to screen |
spreads in rooms via magnetic field |
spreads in rooms via electric field |
field strength decreases when moving away from the source |
field strength decreases when moving away from the source |
emerges when the device is energized (the device must not be switched on) |
emerges when current is consumed (when a device is switched on) |
spread characteristics |
spread characteristics |
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Differently from the static electric and magnetic fields, most electromagnetic fields in the working environment change in time (make several vibrations per minute).
Electromagnetic fields that change in time are generally divided into three zones:
1. low frequency;
2. medium frequency; and
3. high frequency.
The change in time is measured with the frequency unit Hertz (Hz), 1Hz = 1 vibration per second. It is important to be aware of the electromagnetic frequency that a device emits because different maximum tolerances apply for different frequencies (certain frequencies have a more serious effect on people than others).
Static 0 Hz |
Low Frequency 0 - 300 Hz |
Medium Frequency 300 Hz - 100 kHz |
High Frequency 100 kHz - 300 GHz |
electrochemical processes (electrolysis), MRT-devices, electric transport, arc welding |
power network supply: systems with electric motors, transport, welding, energy manufacturing and distribution (substations), furnaces |
dielectric fusers, pulse power suppliers, monitors and screens, induction ovens and heaters, welding units, electrosurgical equipment |
radio and television transmitters, mobile communication (incl. radio transmitters), radars, induction ovens, glue driers, microwave heaters, diathermy |
Health Influences
Official maximum tolerances protect employees mostly against two main health influences:
Also other biological effects have been detected, but as scientists do not have a clear and uniform understanding about their functioning mechanism today, then these have not been calculated into the maximum tolerances yet.
Maximum tolerances regulating professional exposure apply only in the case of acute, short-term influences (up to one workday). Emanating from the limited scientific understanding about the long-term and repetitive exposition, such influence is not covered in the regulation.
Stimulation of the Nervous System
Alternating electromagnetic field generates weak currents in human organism, which gives rise to the ability to have harmful biological effects. Currents appearing in human bodies can have an irritating effect on nerves or muscles.
Thermal Effect
High-power radiation at the radio frequency is a source of heat energy and contact with it brings about all consequences related to the heating of biological organisms: burns, temporary or permanent changes in the reproductive ability, cataract and death. Even though humans can feel warmth with the skin, it is not sufficient for sensing dangerous situations – thermal receptors are located in the skin and cannot sense if the internal organs heat up due to radio frequency. The strength of the electrical current generated inside the body also depends on the body placement in relation to the source of radiation (the angle of penetration).
The effect of the electromagnetic field on the body mostly depends on the strength of the electromagnetic field, the distance of the radiation source and the length of exposure. When it comes to contact with electromagnetic fields, the main risk groups are people with an active or passive medical implants and pregnant women. The people in the risk group are advised to choose such positions and tasks that do not come into contact with large electromagnetic fields (such as welding).
Induction ovens
|
Electrically conductive material is heated with the strong magnetic current; used for blacksmithing, hardening, welding. Operating frequencies from 50Hz – several million Hz. |
Dielectric heating |
Radio frequency (3-50MHz) energy is used for heating. Fields of use: closing and coinage of plastics, glue drying, processing textiles, timber processing. In manufacturing: tarpaulins, plastic lining, shoes, etc. |
Communication and transmitting systems |
Communication systems’ staff do not mostly come into contact with high-power radio frequencies. Exposure is greater in the case of pole technicians and other employees who must work in the vicinity of the transmitting antennas. |
Medical contact |
Medical diathermy applies radio frequency energy to warm tissues. Unshielded electrodes create leakage-electromagnetic fields on high levels. In the case of MRT (magnetic resonance tomography), the staff’s contact with radio frequency fields is not notable as the radio frequency energy has a low power and spreads mostly inside the magnet. |
Even though industrial devices sold in Europe must comply with European safety standards, including regulations about electromagnetic fields, then practice has shown that certain devices could emit so-called leakage-electromagnetic fields, which can influence the human bodies either in certain areas or as a whole. Thus, it is important to periodically monitor and maintain devices applying high electromagnetic currents. Special attention must be paid if pregnant or young women work in the vicinity.
Prevention
By adjusting the factors which influence the employee’s exposure to electromagnetic fields, the dose can be considerably decreased. It is important to protect employees in areas where they spend much time. As people do not sense electromagnetic fields, employees could receive a large share of contact from sources and in places that are irrelevant for the work process. Thus, it is necessary to perform measurements in order to detect the “hot spots” of the workplace and to train employees to apply safe tricks of work. The unnecessary exposure to electromagnetic fields must be immediately stopped. Devices and places with great radiation must be marked with corresponding hazard signs.
Means to Decrease Contact with Electromagnetic Fields
Emanating from the fast increase of electromagnetic fields in living and working environments, and taking into account the limited scientific evidence about their safety, it is not possible to make final conclusions about their safety. Therefore, European Union recommends to apply the principle of caution and, where possible, decrease the electromagnetic fields to the minimum.
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