Limits of Human Exposure to Radiofrequency Electromagnetic Fields in the Frequency Range from 3 KHZ to 300 GHZ - Safety Code 6

Appendix VIII Definitions

• Antenna - A device for radiating or receiving radiofrequency (RF) energy.
• Antenna Gain - The increase in power transmitted or received by a directional antenna when compared to a standard antenna, which is usually an ideal isotropic antenna. Gain is a ratio of powers and may be expressed in decibels (dB) or as a pure number.
• Auditory Effect - Human perception to individual pulses from RF fields in the form of audible clicks, chirping or buzzing sounds, depending on the pulsing regime and intensity of the field ⁽³⁾.
• Cavity - The interior of a metal structure that encloses or confines a radiofrequency field.
• Computerized Tomography - A diagnostic-imaging procedure in which anatomical information is digitally reconstructed from x-radiation transmission data obtained by scanning an anatomical area from many directions.
• Competent Person - An individual who because of his/her knowledge, training and experience is qualified to carry out RF and microwave surveys and/or repair and maintain RF and microwave devices.
• Contact Current - Current flowing between an energized, isolated, conductive (metal) object and ground through an electrical circuit representing the equivalent impedance of the human body.
• Continuous Wave (CW) - Successive oscillations which are identical under steady-state conditions (an unmodulated electromagnetic wave).
• Controlled Environment (area) - A location where there is exposure that may be incurred by persons who are aware of the potential for exposure as a con-comitant of employment, by other cognizant persons, or as the incidental results of transient passage through areas where analysis shows the exposure level may be above those shown in Table 5 but do not exceed those in Table 1 and where the induced currents may exceed the values in Table 7 but do not exceed the values in Table 3.
• Denied Access Area - An area not to be accessed by any person.
• Duty Factor - The ratio of the pulse duration to the pulse period (i.e., time lapse between the start of consecutive pulses) of a periodic pulse train. Mathematically, the duty factor is the product of the pulse duration multiplied by the pulse repetition frequency.
• Effective Isotropically Radiated Power (EIRP) - This term applies to directional antennas. The power that would have to be transmitted by an isotropic antenna to produce the same power density at any given point along the directional antenna's axis. Mathematically, EIRP is the gain of a transmitting antenna multiplied by the net power delivered to the antenna from the connected transmitter.
• Electric Field - The region surrounding an electric charge, in which the magnitude and direction of the force on a hypothetical test charge is defined at any point.
• Electrical Ground - The earth or a metal surface placed in contact with the earth, or connected to the earth with a conductor.
• Electromagnetic Interference - Degradation of the performance of a device, a piece of equipment, or a system caused by an electromagnetic disturbance.
• Electromagnetic Radiation - The propagation of time-varying electric and magnetic fields through space at the velocity of light.
• Extremities - Limbs of the body, including upper arms and thighs.
• Far-Field Zone - The space beyond an imaginary boundary around an antenna. The boundary marks the beginning where the angular field distribution is essentially independent of the distance from the antenna. In this zone, the field has a predominantly planewave character.
• Field Strength - The magnitude of the electric or magnetic field, normally a root-mean-square value.
• Frequency - The number of sinusoidal cycles made by electromagnetic waves in one second; usually expressed in units of hertz (Hz).
• General Public - All persons not employed as RF and microwave exposed workers or those not working in controlled environments (areas). They include pregnant women, the aged, children, the chronically ill and disabled.
• Induced Current - Current induced in a human body exposed to RF fields.
• Interlock - A component or set of components that, when actuated, prevents the generation of power from an RF and microwave source, such as the magnetron in a microwave oven or an RF transmitter.
• Leakage Radiation - Any unintended or accidental radiation emitted by a device outside its external surface.
• Magnetic Field - A region of space surrounding a moving charge (e.g., in a conductor) being defined at any point by the force that would be experienced by another hypothetical moving charge. A magnetic field exerts a force on charged particles only if they are in motion, and charged particles produce magnetic fields only when they are in motion.
• Magnetic Resonance Imaging - A technique for obtaining images of the internal anatomy based on the use of nuclear magnetic resonance (NMR) signals. The NMR method is based on partially aligning the nuclear spins by use of strong, static magnetic field, stimulating these spins with an RF field oscillating at the precession frequency of nuclear magnetic moments, and detecting the signal that is induced at this frequency.
• Microwave - A radio wave which has a frequency of between 1 GHz and 300 GHz or a wavelength of between 30 cm and 1 mm.
• Modulated Wave (radiation) - An electromagnetic wave which is modified by pulsing, or by varying its amplitude, frequency or phase. Such a wave is called, respectively, pulse-, amplitude-, frequency-, or phase-modulated.
• Near-Field Zone - A volume of space generally close to an antenna or other radiating structure, in which the electric and magnetic fields do not have a substantially plane-wave character, but vary considerably from point to point. The near-field zone is further subdivided into the reactive near-field region and the radiating near-field region.
• Occupationally Exposed Persons - Workers who are exposed to RF fields and microwaves in the course of their regular employment.
• Organ-averaged SAR for the eye - Specific Absorption Rate (SAR) averaged throughout the whole eye ball.
• Owner - A person, organization or institution having title to, or, an administrative control over a given RF emitting device.
• Plane Wave Character - Nature of the angular field distribution in the far-field region of a source antenna, in which the electric field vector is perpendicular to the magnetic field vector, and they are both perpendicular to the direction of propagation.
• Power Density - The rate of flow of electromagnetic energy per unit surface area usually expressed in W/m² or mW/cm² or µW/cm².
• Portable Transmitter - A mobile device that radiates electromagnetic waves for the purpose of communication, examples of which are cellular telephones and walkie-talkies.
• Radiofrequency - The frequency in the portion of the electromagnetic spectrum that is between 3 kHz and 300 GHz.
• Radiation (electromagnetic) - The emission or transfer of energy through space in the form of electromagnetic waves.
• Radiating Near-Field Region - The region between the reactive near-field and the far-field wherein the radiation field dominates the reactive fiel d, but lacks substantial plane-wave character.
• Reactive Near-Field Region - The region that is closest to an antenna or other radiating structure and contains most or nearly all of the stored energy.
• Responsible User - A person who is authorized to operate an RF device properly and safely with respect to RF radiation.
• Restricted Occupancy - An area where access is restricted to RF and microwave exposed workers for a prescribed time duration.
• RF Device - A device which generates and/or utilizes RF energy.
• RF Survey - An evaluation of the actual or potential RF field levels in any area, specifically in the vicinity of RF devices, and an evaluation of induced and contact currents.
• RF Worker - An employee or a person (including a pregnant woman) who because of his/her knowledge, training and experience with RF devices is qualified to work with these devices properly and safely with respect to RF exposure.
• RF and Microwave Exposed Workers - Persons who are exposed to RF fields and microwaves in the course of their daily work (e.g., those who may work near an RF device but may not be RF workers).
• rms - Root mean square. Mathematically, it is the square root of the average of the square of the instantaneous field or current taken throughout one period.
• Safety - The absence of detrimental health effects from RF exposures.
• Safety Officer - A person who is appointed to ensure safety of working within an RF environment.
• Specific Absorption Rate (SAR) - The rate of radiofrequency energy absorbed in tissue per unit mass. Quantitatively, it is the time derivative (rate) of the incremental energy (dW) absorbed by an incremental mass (dm) contained in a volume element (dV) of given mass density (p).

SAR is expressed in units of watts per kilogram (W/kg). Also

where σ is the tissue conductivity (S/m), E is the rms electric field strength induced in the tissue (V/m) and p is the mass density (kg/m³).

• SI - An acronym of Système International d'Unités (International System of Units).
• Transceiver - A combination of transmitter and receiver in a single housing, with some components being used by both parts.
• Uncontrolled Area - Any area that is neither a Restricted Occupancy Area, nor a Denied Access Area.
• Visible Warning Indicator - A display such as flashing lights and signs to warn people of the fact that the power of an RF device is on.
• Wavelength - The distance travelled by a propagating wave in one cycle of oscillation.
• X-Radiation - Electromagnetic radiation having a wavelength in the range of 0.0001 to less than 1 nm.